Just had my th350 rebuilt ,, new clutches sprag bands,, pump -- whole deal,,,,,, got a new coan converter,,,, drove to 1 car show and did not make it home!! made it 28 miles
made it 28 miles
made it 28 miles


MAN I AM PISSED

shifted to 2nd gear and free wheel!! Flatbed to tranny shop



now tranny shop says the sprag is detonated ,,, that it is my fault for abuse ,,, hott rodding ,, to many hole shots,, and downshifting,,, ect

and wont warranty it!!!




how bad did i get screwed ????????



no names but I wouldnt go to the tranny shop that is real close to Auto city speedway in Clio Mt Morris Michigan area if i were any of you

Where you hotrodding it and making really harsh shifts? Just because it is new rebuilt doesnt mean its unbreakable. What engine are you running?

They have no warrantly policy on new rebuilds? Any reputable shop should...

Most transmission shops do not warranty "racing" transmissions. If you asked them put a "shift kit" in it, it became a "racing" transmission.

How long since they rebuilt it?

Have you done any burnouts?

When it broke (or seemed to) was it a WOT run or something less?

TH350's in stock form are pretty tough. The intermediate sprag is a known weak point but the key is to keep the 1-2 shifts from being too brutal.

If the trans shop did their own valve body/accumulator mods or used a B&M valve body kit at max settings they may have actually caused the failure.

1-2 accumulator spring should always be in place. Intermediate wave steel should always be retained.

1-2 feed hole should not be over .135" and the checkball should be left in place. Pretty much stock calibration, increased line pressure and slightly increased orfice sizing makes for a firm shift without damaging parts.

Any good shop should do at least a 6 month/6000 mile warranty IMHO and experience..
How can they prove it wasn't their faulty work at 29 miles?

Any good shop should do at least a 6 month/6000 mile warranty IMHO and experience..
How can they prove it wasn't their faulty work at 29 miles?

Chris,
I agree. I warranty my racing units for 90 days and street/strip stuff for 6 months. I "take care" of guys for longer than that. I have a 10 second GN unit in the shop now that is over a yr old and it won't cost the guy anything for me to fix it, except fluid and his R&R time.

However,
Most shops simply don't want to mess with performance work. You have to find a shop that does, and then they will usually warranty it. Many shops will not warranty a bench rebuild anymore. They have no control over whether you use a new converter, flush the cooling lines, properly seat the converter, etc.

29 miles over what time period?
Did the guy buy it 2 yrs ago and just now put it in? I cover guys in this case, let me know when you get it running, and I'll start a warranty then. However we don't know all the details here.

If I were guessing, I bet the shop "hotrodded" the trans and either installed the B&M kit on Street/strip mode with the feed holes drilled to 3/16 and no checkballs, or they removed the 1-2 accum spring and drill the feed holes big, and left out all the cushion plates, particularly the intermediate.
Old school tricks that are proven to break these units.

How hard did it shift to 2nd at light to medium throttle?

It lasted 1 day,, I made it 29 miles,,, I did 1 burnout ,,, I am running a zz4 crate motor ,,373 rear and a coan converter 3000 stl,,,, stopped working on a normal 1st to 2nd shift,, it was converted to full manual,,,, with a zz4 I cant be to hard on it its only 355 horse,,,,,,, it was supose to have a 1 year warranty,,, and I had it built to handle 500 hp 500 tq and 7500 rpm ,, with all the parts put in it ,,,,, it should have been somewhat bulitproof,,,, And I run street tires on it

As a side note from experience.
A TH350 seems to hold up best when it is closest to stock.

I think an absolutely stock TH350 rebuilt with proper clearances, and no mods except the dual feed would take 500 HP all day every day. I know this from experience. I've seen them stock live at near 500 until they start to drive through the 3rd gear clutches.

It lasted 1 day,, I made it 29 miles,,, I did 1 burnout ,,, I am running a zz4 crate motor ,,373 rear and a coan converter 3000 stl,,,, stopped working on a normal 1st to 2nd shift,, it was converted to full manual,,,, with a zz4 I cant be to hard on it its only 355 horse,,,,,,, it was supose to have a 1 year warranty,,, and I had it built to handle 500 hp 500 tq and 7500 rpm ,, with all the parts put in it ,,,,, it should have been somewhat bulitproof,,,, And I run street tires on it

Ya,
Sounds like it should have been overbuilt for the engine you have.
You may have broken it on the burnout. What gear did you burnout in, and during the burnout how did you shift (if you did). i.e. did you start out in 1st and shift to 2nd while spinning at WOT? Did it hook hard while spinning in 2nd?

Did they install a 36 element sprag and drum? Spiral retaining ring on the sprag retaining plate?

Why full manual? You don't have a combo to warrant full manual IMO.
What VB?

I was just gonna say the stock 350 with the cheap transgo kit lasted me 4 years of totally beating the hell out of it,,,,,,,,,


The tranny failed on a 1 to 2nd shift at 3200 rpm...

overhall kit 170
band 18
bushing kit 35
planetary unit 35
pump bushing 4
sprag 60
shift kit 85
converter 428

that is my part slist wich was put in it

the total with them r=r was 1175.40

kit is a transgo,,, what should i have go tfor 850???

The TransGo kit definitely won't hurt the sprag. If anything it is a little conservative IMO.

I would question whether it even has the TG kit. Look for a black anodized plate between the VB and case.

$35 for a bushing "kit" and an additional $4 for a pump bushing? WTF? Prices are OK, but you got charge twice for a pump bushing. They are included in the "kit". Maybe the fouled it up and charged you for it. LOL

$60 for a sprag... What does that include? Is that a low reverse roller clutch assembly from a 700-r4 as an upgrade, or is that a hardened intermediate outer sprag race?

Not a bad price if the trans had lasted....
If they installed it and all, I would threaten to take them to small claims. It isn't worth their time. Does your reciept have a warranty on it?

They can't prove you abused it and they can't prove they built it right. Make em fix it..
they should anway...

Did a burnout on street tires 1st to second at about 5800 to 3rd at about 5800,, and let car drift down the road for about 200 feet then let off



When I got it,,,,,,,,, the 1st to 2nd seemed kinda spongy -not snappy,, if that tells you guys anything

Ya,
It does actually sound as if you broke it on the burnout.

In the future,
do not do a WOT 1-2 burnout, get tires spinning in 1st, shift to 2nd at moderate throttle, accelerate, shift to 3rd, and do your burnout in 3rd.
Most trans shops don't even know this, but the 1-2 shift at high rpm during burnout is brutal on the sprag. As you've learned the hard way.

If it were one of my units, I would fix it, however IMO you broke the transmission due to "abuse".

However a 500 HP capable Th350 would include a 36 element sprag/drum assembly IMO too, and your's likely doesn't have this, not at that price.

Did burnouts like that ,, bout 2 sets of tires a summer for -- 4 years on the stock 350 with the cheap transgo kit in it,,, with no problem,,, I took the tranny in to get beefed up for bigger heads cam,,ect on my motor.... Seems it should of held 1 burnout......

My union lawyer made 1 phone call justa while ago,,, and now he is goin to warranty the tranny!! Thank god


And the guy is also digging through the pile of recycling junk to FIND my old parts


because I was told they didnt keep em when i picked it up.....

The way the TH350 operates, it can kill a sprag when you do burnouts that way.
IMO, ya it SHOULD handle a burnout. It sucks to break one on the first burnout. However my point is, be careful how you do them in the future.
No matter what, this is a pain for you, as well as the builder so you don't want to repeat it.

An old worn out TH350 isn't going to shift as hard (all else being equal) as a freshly built one with new clutches, etc. The difference may be the trans was new, so it is mechanically working better and now broke a sprag although it never has before.

There are many posts on this forum about proper burnouts with a GM 3 speed automatic. I would suggest you read up a bit. I've posted on the subject before.

Another thing,
and it is a hunch on my part, but the hardened sprag race commonly used in TH350s, is heat treated to be harder than stock.
My theory is this MAY actually make it more brittle.
I know from speaking with some very knowledgeable guys, one who occasionally posts here and works for a big name trans company, that some heat treat this part to actually soften it a bit on the Rockwell. Less brittle?


Get it fixed and good luck with it.

HEY Jake,,,,, how much should the 36 elementl sprag cost me???


thanks

They are $300 and up from most vendors. I have them for less.

email me

jakeshoe@yahoo.com

Stopped up there today and the guy who built it said he owed me an APOLOGY>>>>> Turns out it was coans fault,,, something he said came unglued inside the converter and busted the gear in the pump,, then ping- pong from there,,,,,, both sprags were completely OK,,, but thats about all that survived inside,, but now I need a new CASE,, and I have to wait for the converter to go back to coan and have a new one built again!!!!!!!!!!!!!!!

Well even though you have to wait, at least it will be taken care of.

I agree they should back it up!!
i bought my built 350 8 yrs ago and told them up front gonna drop about a 475 hp sb in front of it with a 3000-3500 stahl and do some weekend 1/4 mile fun with it i beat on it from day one with shifts from 1-2nd at 6000 rpm and 2-3 at 6000-7000 and it still runs great no problems as of yet!!