:( Well I did today !

First Time Trial ran a nice 10.390 at 129.48 at 6800 RPM (with my 850 DP Carb with Choke Horn (Bob and Chris ;) and my new HEI distributor with MSD rev limiter module but NO MSD Box)

BUT I felt a strong vibration from the Rear of the Car that came on when I let out of it. This is a new thing since my rear was re-done 4 passes ago. OK so I take the wheels off, check the c-clip eliminators, axles look in the right position, I take the driveshaft off and re-set it in the pinion, pinion nut good, Check everything except pull the rear cover off. Can't find anything except when the rear was done, the guy who did it for me (I don't do them on my back) tightened the U-Joint strap Bolts to at least 60 ft lbs and they should be around 15...maybe the needle bearings weren't rolling right when under the extra load by the strap..maybe..maybe..I have to see what happens..

First Round comes up, I nail the tree, my opponent (10.05 dial-in) isn't anywhere to be found, so I let out at 1000 ft and a bang comes from under my seat and the smoke show begins.

Cracked trans case right above the cooler ports and a waterfall of fluid cometh onto the ground...Glad I kept it under control as the fluid got under my rear tires.

I figure the vibration stressed the case so much it just couldn't hack it..Ultra-bell here I come....I was going to anyway with the next freshening..

I did win the race, but had to go home...:sad:

I need to pull the rear apart and hope something is obvious..

Any comments or previous experience..feel free to let it loose

Only two things come to mind.
1) Ouch.
2) You probably shouldn't just try to "drive through" what you were
pretty sure was a drivetrain problem. Good way to put yourself, and maybe the other guy, into a wall?
Glad you didn't get hurt.

I popped a case in half, at the track no less, right around the torque convertor area.
I built a new engine and was going to track test it, somehow over the winter my driveshaft must have been leaning on the wall and fell, it had a slight wobble in it...couldnt figure out where the vibration was from at first, i thought it was the bias ply slicks i wasnt used too...

ak

I popped a case in half, at the track no less, right around the torque convertor area.
I built a new engine and was going to track test it, somehow over the winter my driveshaft must have been leaning on the wall and fell, it had a slight wobble in it...couldnt figure out where the vibration was from at first, i thought it was the bias ply slicks i wasnt used too...

ak

I put new tires on for this race and balanced them and checked them at two different places different friends work to make sure they would spin true....they did.

Anyway, I really thought I found the problem with the possible crunching U-joints. The guy who set up my rear does dozens of them every year for the racers at my track and that Denny's Driveshafts was pretty adament about the 15 ft/lb maximum on the bolts. I am going to send the driveshaft out to them to check it just to rule it out.

Bummer Tom!!

I guess the bright side is ya didn't get into your trans fluid which could have been real nasty. I would have thought that your th400 would have been up to the task. Maybe just one to many hard launches. What kinda of trans mount do ya run?

I don't have to worry about such things with a weak old s/b!LOL

BTW ya got the Monte hauling the mail!!!

David

Bummer Tom!!

I guess the bright side is ya didn't get into your trans fluid which could have been real nasty. I would have thought that your th400 would have been up to the task. Maybe just one to many hard launches. What kinda of trans mount do ya run?

I don't have to worry about such things with a weak old s/b!LOL

BTW ya got the Monte hauling the mail!!!

David

Thanks Dave

The trans was probably up to the task except the vibration was pretty bad that last time and I had already decided win or lose that I was going home if the vibration was still there after adjusting the U-joint strap bolts....But that didn't seem to be it.

The transmission internals are set up for 1200+ HP, but the case was a GM stocker.

I have solid motor mounts and a rubber trans mount...

I went to 35 spline Mark Williams stuff, Pro-Gears and a spool as the last piece of the puzzle before I uncork this motor and exhaust into the high 9's on the street with pump gas.

Way off the subject here but at the super chevy show a few weeks ago I saw a car run a low 10 and as soon as he hit the brake at the finish line the drivers side brake locks up and takes him from the right lane over into the other guy's lane which he clips the other guy and hits the wall at 130+ mph. There was not much left of his car but nobody got hurt.

If the crack is into the fluid passages, I think it's beyond hopes of a Super Bell fix. Besides having all of the mounting ears hel-i-arc'd at one time or another, my old Fairbanks TH400, sustained a crack all of the way past the front pump gasket area. It was questionable whether welding it would work, as only the external damage was visible/accessible.

With the pump out, it appeared that the crack was limited to the outer shell, however, it did breach one rectangular passage, behind the pump.

I reassembled the tranny and took it to my dad's, he is an Operating Engineer (Welding Supervisor/Forman) at the Nevada Test Site, and has a nice TIG set up at home. After torqueing everthing to spec (avoid warpage), he drilled/ground a little hole at the end of the crack to keep it from running further, then welded the hole back up. Little tacks were incremently placed the full length of the crack, starting in the critical area, where the pump gasket and o-ring are expected to seal. Finally the rest was filled in, while I tried to keep the case cool with a wet towel.

I pulled the pump back off to make sure that there wasn't any disfigurement of the sealing surfaces, which there were not. I had a couple of months of anxiety, because I was swapping my drivetrain from my wrecked '66 (cause of the crack), to my then, newly acquired '66 (2002-3). A couple of months later, it was up and running, good as new. I remember that the first drive had a shift abnormality, no shift or something. For a moment, I thought, "CRAP, looks like I'll be buying a new tranny". But, after manually shifting through the gears once, all returned to normal

Just thought I'd share that, maybe give you a little hope of salvaging your existing case. Too bad you're halfway across the world, I have a TH400 sitting in the backyard. Fortunately TH400 cores/cases are still pretty cheap and abundant.

If the u-joint caps and needles look good, check your pinion angle.

Good Luck

Tom,
Sorry to hear your tranny issues continue but very glad that you were able to get it stopped safely.
We all know crap happens quickly at these speeds. :(

The theory that the u-joint caps being too tight causing a vibration is almost comical IMO. U-joint caps would more likely crack before they would distort enough to cause an issue. If they were an issue, it would have shown up immediately.

Your vibration was more than likely caused by the trans bellhousing bolts being loose, or the case was already cracked and causing the vibration.

Bad news is, you need to check the pump gears, replace the bushings, and probably the stator bushings in the trans. Check the stator tube for square to the pump.

You need to also have the converter hub checked for cracks and runout.

Tom,
I broke two in two weeks when I first built my Camaro drag car. I could not figure it out, nor could my trans builder. There was no vibration whatsoever that I could feel at 7500 rpm. Just for grins, after the second case I took the driveshaft to a local driveline shop and he told me that it was slightly bent and out of balance :( Had a new shaft made and never had another problem. Put almost 3500 runs on the car before I sold it. Cant swear that it was the driveshaft, but that is the only thing changed and the problem went away.

Tom, why the old 850 DP? Guess it runs as good as the high-end stuff?

Sorry to hear the bad news Tom,sounds like the case may have already been cracked or the bellhousing bolts came loose.How was the weather up at LVD today.I got up at 5:30AM and the weather report on LVD website showed t/showers all morning after that I went to take a shower and had no water and by the time I was done messing with the well pump it was to late to go anyway.
Vinny

The theory that the u-joint caps being too tight causing a vibration is almost comical IMO. U-joint caps would more likely crack before they would distort enough to cause an issue. If they were an issue, it would have shown up immediately.

Your vibration was more than likely caused by the trans bellhousing bolts being loose, or the case was already cracked and causing the vibration.

Bad news is, you need to check the pump gears, replace the bushings, and probably the stator bushings in the trans. Check the stator tube for square to the pump.

You need to also have the converter hub checked for cracks and runout.


The trans had 250 passes on it since 2005, This happened on the FIRST Pass after the Rear End Was Re-Done last Fall. I had new tires at the same time that I made the first pass with the new rear. Felt like out of balance tires only made 2 passes last Fall. First time out today with new absolutely balanced tires I get it again....After first pass, the only thing I find is way overtorqued U-joint bolts.

I'd say the FIRST Pass Is quite IMMEDIATE Wouldn't You ?????

The Bell Housing Bolts WERE and STILL are ALL TIGHT As I checked them FRIDAY (36 hours ago), along with every other conceivable bolt and connection on the car.

That to me is Comical .

Cracked Case Already - NO Way !

I cannot believe the Trans caused the Vibration, the Vibration Hurt the Trans..If I am wrong so be it and I'll report it.

I am pretty confident it lies in the pumpkin.

OR

My driveshaft got dropped and he didn't tell me about it.

Tom, why the old 850 DP? Guess it runs as good as the high-end stuff?

Ain't that the truth !! That 4781-C Carb has been like a best friend. It repeats and repeats everytime. When it (or if) it gets retired it will be placed on the mantle over the fireplace under plexiglass !!

I sold off my HP's and will be feeding with a dominator and a Super Victor (Bill B :thumbsup: ) or Dart intake matched to my Heads Once I put in the much needed new cam and get rid of my 2 1/2" mufflers...Time to make some noise..LOL

Tom,
I broke two in two weeks when I first built my Camaro drag car. I could not figure it out, nor could my trans builder. There was no vibration whatsoever that I could feel at 7500 rpm. Just for grins, after the second case I took the driveshaft to a local driveline shop and he told me that it was slightly bent and out of balance :( Had a new shaft made and never had another problem. Put almost 3500 runs on the car before I sold it. Cant swear that it was the driveshaft, but that is the only thing changed and the problem went away.

Thanks for the Info Bill,

I will send mine back to Denny's Driveshafts for a check. I am wondering if my driveshaft got dropped and was never told.

Sorry to hear the bad news Tom,sounds like the case may have already been cracked or the bellhousing bolts came loose.How was the weather up at LVD today.I got up at 5:30AM and the weather report on LVD website showed t/showers all morning after that I went to take a shower and had no water and by the time I was done messing with the well pump it was to late to go anyway.
Vinny

Thanks Vinny,

Turned out the rain came and cancelled the rest of the race in the 3rd round..A couple oil-downs limited everyone to 1 time trial. As you might have read in my response to Jake, not the bolts and I really doubt the case. I am really thinking the driveshaft got messed up somehow because I really don't think he would have messed up something in the ring and pinion setup...but there is always the possibility, maybe a cap wasn't tightened? Pinion bearing not seated properly, I am only guessing until I get it apart...

First the driveshaft to Denny's for a check.

Tom, a cracked transmission case is almost always the result of driveshaft out of balance.

Tom,
this story is one of many that are the reason why i do all of my own work. if the guy doesnt know not to torque the u-joint bolts to more then 15ft-lbs, then what else does he not know?
brian

Tom,

Sorry to hear about the trans. failure. Seems it's a little contageous (broke mine last weekend) around here. Good luck getting to the bottom of it and getting back on the track.

Are any of those broken cases from 1969 TH400,s? I once read that the alloy was changed to something cheaper that year. I don't know that as a fact. Perhaps someone else does.

If it isn't the result of loose bell bolts, it was more likely a driveshaft balance/runout issue. Very unlikely to be the the result of the u-joint straps being too tight. The straps would more likely strip/break before causing damage to a u-joint.

There are many reasons a trans bell can crack and the most common ones have been stated but there are also dowel pin issues, converter issues, internal transmissions issues, trans mounting, fatigue, improper installation, etc.

A crack could have started when the trans was installed from a burr on the dowel pin or bellhousing mating flange and just now have shown up as it progressively got worse or spread within the time of the last 3 or 4 passes. Cast aluminum is somewhat brittle and the last TH400 used in regular production was 1990, almost 20 yrs ago. I would bet your core is even older than that. Plenty of time to fatigue or have been installed/removed multiple times.

Hmmmm.
Nothing broke in the drivetrain?
Front u-joint is ok? Front yoke is ok?
Rear u-joint?
Of course if you remember, I broke the front yoke, u-joint, and driveline. Got the T-shirt, got the smoke, got the severe driveline vibration on the prior run..... and broke the case all to ****. The big bang theory.

Are you running solid mounts on the engine? Solid on the trans? (I doubt it)

The TH400 case is weak right where yours broke....but it needs something out of alignment or something to break behind it to cause this.
On mine, there was only one bellhousing bolt holding the trans in....the case busted around all the rest.

The ultra bell is an easy install. Find a BOP TH 400, and go for it. PM me and I'll share my install...it's pretty simple.

Sorry to hear of the carnage....but glad you didn't crash my freind! We hate when we hear that!

Ron

Don't worry about finding a BOP case, I have plenty of cases here that can use an Ultra-Bell, just pay shipping. LOL

Tom,sorry to hear about all this :eek:
Glad you are all right...thats scary stuff!

Tom sorry to hear about the broken trans. I broke the case on my powerglide when I first took the car out and it was due to the wrong joint on the driveshaft. The car also had a solid rear mount that quickly went in the trash. The driveshaft vibration at that speed was enough to crack the case from the pan rail up and over the top of the case.

Tom,
this story is one of many that are the reason why i do all of my own work. if the guy doesnt know not to torque the u-joint bolts to more then 15ft-lbs, then what else does he not know?
brian


I agree Brian,

Time Time and Time is always my foe. with my regular job, 3 kids all under 12, and at the time it was done I was coaching Pop Warner football heading to the playoffs, some things have to be farmed out or they will never get done. Transmissions and Rear ends are about the only things I don't do.

Thanks to all for the positive information....

My car rode like Glass until the rear gear swap..

I am anxious to get the driveshaft sent out and checked...no matter what happened to the Trans, I need to get tothe bottom of the source of the vibration..

I'll get the shaft sent out on Tuesday and keep everyone posted...

Tom, a cracked transmission case is almost always the result of driveshaft out of balance.

Thanks Ed, My main goal here is to find the cause of the Vibration..Transmissions can be removed fixed and reinstalled..

Diagnosis can take way more Time so I have my fingers crossed that it is the issue.

Don't worry about finding a BOP case, I have plenty of cases here that can use an Ultra-Bell, just pay shipping. LOL

Thanks Jake, I'll keep that in Mind. Wouldn't you know I got rid of 3 Chevy TH400 cores and 1 BOP core last Fall...:(

I Can't let it get to me, because if it makes me stressed, it isn't fun anymore, this is supposed to be enjoyable.

I have 3 empty good BOP cases and 2 Chevy cases that have a small peice missing from the bell. Any would be a good candidate for an ultrabell. I buy the early model cores even if they are busted because they have the good direct drums that I need for the 34 element sprag.

You have to be careful buying those drums from the supply places beause often they have been reground and the inner race is smaller diameter, the sprag can roll over in a HD application.

I have 3 empty good BOP cases and 2 Chevy cases that have a small peice missing from the bell. Any would be a good candidate for an ultrabell. I buy the early model cores even if they are busted because they have the good direct drums that I need for the 34 element sprag.

You have to be careful buying those drums from the supply places beause often they have been reground and the inner race is smaller diameter, the sprag can roll over in a HD application.

This trans has a 36 element and drum, would that be a problem for the BOP Case?

Don't the '63-'67 TH400's also have a steel center support, while later models use aluminum (or other alloy)? And, of course, the box type filter.

This trans has a 36 element and drum, would that be a problem for the BOP Case?

No,Not at all.

The early TH400's whether they were Chevy, Caddy, or BOP used an actual sprag type element, and those direct drums are different. The case itself makes no difference. I rarely build a BOP trans and the cases are dime a dozen, the Chevy cases are harder to find and I build alot of those.

You have a 36 or 34 element setup? The 34 element is the common upgrade, the 36 element is like the Coan "Super Drum". The case will still work but the 36 element setup requires different steel plates that have to also be machined, a specific intermediate pressure plate, and different intermediate friction clutches. These aren't standard TH400 parts. So just be sure whoever assembles it knows this and gets it right if it is the 36 element setup.

Don't the '63-'67 TH400's also have a steel center support, while later models use aluminum (or other alloy)? And, of course, the box type filter.

TH400's started in 1964. Center supports have always been made of cast iron. Some models used a steel apply piston. Nothing to be concerned with.

Later models had a change on the center support machining to use a fretting ring between the case and CS to prevent wear to the case.

if you're going to put an Ultra Bell on it why start with the Chevy case? BOP 400's aren't hard to get.

I prefer to use a case that needs a new bellhousing...Plenty of those around.

No,Not at all.

The early TH400's whether they were Chevy, Caddy, or BOP used an actual sprag type element, and those direct drums are different. The case itself makes no difference. I rarely build a BOP trans and the cases are dime a dozen, the Chevy cases are harder to find and I build alot of those.

You have a 36 or 34 element setup? The 34 element is the common upgrade, the 36 element is like the Coan "Super Drum". The case will still work but the 36 element setup requires different steel plates that have to also be machined, a specific intermediate pressure plate, and different intermediate friction clutches. These aren't standard TH400 parts. So just be sure whoever assembles it knows this and gets it right if it is the 36 element setup.

Yup, that's what I got 36 Element Sprag with Super Drum..Dynamic Transmissions did this Trans and it has worked flawlessly for the two seasons I have had it. Was going to get it freshened this coming winter along with my Converter...Guess I can do that now...LOL...Dynamic will be getting the Trans back in a week or so.

I only expected 50 passes this season witht he Monte as it will be down a lot getting many upgrades...so I didn't do the freshening this past winter.

There is a 34 element in my Fresh TH400 and Coan converter sitting on my garage floor ready for the Chevelle..

It will be a few weeks before I get the trans out as I have to focus on my Chevelle Motor as I have a Dyno appointment for Saturday. Let's see there are 4 baseball games for my kids that have to fit in there too :confused:

Summertime fun! :eek:

Sorry to hear Tom.

Summertime fun! :eek:

Sorry to hear Tom.


Hey Gene, Good to hear from you. Hope all is well !!!

Tom,
this story is one of many that are the reason why i do all of my own work. if the guy doesnt know not to torque the u-joint bolts to more then 15ft-lbs, then what else does he not know?
brianSo are you saying that regardless of what U-joints people run, that 15 FT/LBS is not to be exceeded? Maybe I'm missing something here, and kindly point it out to me if I am, but I must ask you guys something.... so what if you have 1350 series Spicer U-joints with 3/8" U-bolts? Are you saying that the nuts on those should also be torqued to merely 15 FT/LBS? You mean to say that the bearing cups cannot survive the torque spec on 3/8" fasteners of 30-40 FT/LBS? If that is the case then why would the manufacture use 3/8" U-bolts instead of something smaller?

http://www.chevelles.com/showroom/data/500/medium/Broken_trans_case_from_side.JPG

Look familiar???

I was concerned about the 235 PSI pressure in my transmission being too high, and FWIW the tech guy at the place I bought it from said that TH400 cases can break when you take the pressure above 250 PSI. He said that below that, the case should be fine. I wonder if that's a factor here in your case (no pun intended:D). Tom, did your transmission shift really hard?

So are you saying that regardless of what U-joints people run, that 15 FT/LBS is not to be exceeded? Maybe I'm missing something here, and kindly point it out to me if I am, but I must ask you guys something.... so what if you have 1350 series Spicer U-joints with 3/8" U-bolts? Are you saying that the nuts on those should also be torqued to merely 15 FT/LBS? You mean to say that the bearing cups cannot survive the torque spec on 3/8" fasteners of 30-40 FT/LBS? If that is the case then why would the manufacture use 3/8" U-bolts instead of something smaller?

Go to Denny's driveshaft website and take a look. It's not the yield of the fastener, it's the fact you are clamping a needle bearing.

I think they say 15-18 ft/lbs and is what I set mine to last year and the driveshaft is still swinging around.

http://www.chevelles.com/showroom/data/500/medium/Broken_trans_case_from_side.JPG

Look familiar???

Hey, how did you find my house so quick ???

What was the final conclusion on the cause ?

Thanks

Tom

I just looked on the Denny's website...

it says 17 FT/LBS for the 1310 and the 1330 series U-joints, and 20 ft/LBS for the 1350 U-joints. Hmmm, I never knew that. You would think that every driveshaft manufacture would tell you that. Thanks for the info Doug. :thumbsup:

I guess now that I've really muscled the U-bolt nuts tight on the 1350 series U-joints on my car, I should go back and lossen them up before I begin driving it around.

I was concerned about the 235 PSI pressure in my transmission being too high, and FWIW the tech guy at the place I bought it from said that TH400 cases can break when you take the pressure above 250 PSI. He said that below that, the case should be fine. I wonder if that's a factor here in your case (no pun intended:D). Tom, did your transmission shift really hard?

Hey Billy,

Trans shifted firm but not hard.. Wherever the vibration came from is likely what did in the trans.

Tom, I never decided for sure what happened. See an earlier post that discusses it. I really think the case broke and put undo load on the rear main which caused it to fail which in turn took out rods #7 & 8 which in turn took out the block crank etc.
butttt,
it may have happened the other way around.
Either way it was a $12,000.00 pass!!!!!!!!!!!!!!!!!!

I was concerned about the 235 PSI pressure in my transmission being too high, and FWIW the tech guy at the place I bought it from said that TH400 cases can break when you take the pressure above 250 PSI. He said that below that, the case should be fine. I wonder if that's a factor here in your case (no pun intended:D). Tom, did your transmission shift really hard?
Excess pressure in the TH400 doesn't cause the bellhousing to break, it causes the case lugs inside to be blown out on a 1-2 shift. If it is a full manual transmission and not using an intermediate band, there is a fix for this.

250 psi is the commonly quoted limit.

Too much pressure can cause other issues too, engine thrust bearing problems, converter ballooning, etc.

Excess pressure in the TH400 doesn't cause the bellhousing to break, it causes the case lugs inside to be blown out on a 1-2 shift. If it is a full manual transmission and not using an intermediate band, there is a fix for this.

250 psi is the commonly quoted limit.

Too much pressure can cause other issues too, engine thrust bearing problems, converter ballooning, etc.Thanks for that info Jake. I stand corrected. ;)

I broke a TH350 a couple of weeks ago. Not like you would think though. It fell 4 feet to the floor with a transfer case still hooked to it :eek: Since then I have modified my new jack to be able keep it in place and learned the motorcycle straps hols much better than any chain could. The jack worked a lot better putting in the new TH350 and NP205. I swear that 205 weighs more than a TH350 :eek:

A couple of years ago the 400 in Old Blue cracked on a maintenance run. You could tell that the crack was already started once we got it apart. Pretty dang scary to hear the big thump and then see all that smoke and fluid dumping out behind the car. :eek:

So are you saying that regardless of what U-joints people run, that 15 FT/LBS is not to be exceeded? Maybe I'm missing something here, and kindly point it out to me if I am, but I must ask you guys something.... so what if you have 1350 series Spicer U-joints with 3/8" U-bolts? Are you saying that the nuts on those should also be torqued to merely 15 FT/LBS? You mean to say that the bearing cups cannot survive the torque spec on 3/8" fasteners of 30-40 FT/LBS? If that is the case then why would the manufacture use 3/8" U-bolts instead of something smaller?

I like my U-joint caps concentric ;)

I like my U-joint caps concentric ;)LOL...I hear ya.:D

Yep, Denny (from Denny's Driveshafts) told me to torque the U-bolts to 1/4 turn past the point where there was no slack. I've been religious about keeping that torque value when taking the D/S in and out.

Tom,
Sorry to hear of the breakage, but as was stated before,...at least nobody got hurt. That kind of breakage has the potential to be disaterous.
FYI....I torque my 1350 u-bolts to 17 ft-lbs. :)
So, have you at least inspected the driveshaft and rear u-joint yet?
I just got rid of my driveshaft because it was trying to "jump rope" under my car. I went with a 3.5" aluminum.

Tom,
Sorry to hear of the breakage, but as was stated before,...at least nobody got hurt. That kind of breakage has the potential to be disaterous.
FYI....I torque my 1350 u-bolts to 17 ft-lbs. :)
So, have you at least inspected the driveshaft and rear u-joint yet?
I just got rid of my driveshaft because it was trying to "jump rope" under my car. I went with a 3.5" aluminum.

Thanks Jim,

I have not looked at anything yet, maybe tomorrow.