Team Chevelle banner

Transmission Advice and Recommendations

1K views 14 replies 8 participants last post by  Kirk's67SS 
#1 ·
Hi Everyone,
I have a new 383 stroker that is rated around 420+ horsepower and 470+ftlbs of torque. I have a newly rebuilt 10 bolt with Yukon DuraGrip, Ten Performance by Motive Axles and 3:73 US gears. I have a 400TH transmission with a shift kit. I’m not sure if it was just a shift improver kit or the Transpak kit. The PO didn’t know. When I installed the new engine, I replaced the converter with a TCI Breakaway one. (About 1000 rpm over stock). The transmission seems to be working well. It has a good firm shift from 1-2, but 2-3 is almost unnoticeable, however, it is definitely shifting into 3rd. I’ve dropped the pan a few times, replaced the filter and refilled with B&M trick shift fluid. I have noticed when I manually shift around 3k, I hear a whistle type sound. Otherwise it seems to do pretty well. I have been chasing a vibration while in gear stopped normally on a hill. I also have been hearing an exhaust leak sound from the converter area. I think I found the culprit for the vibration, which was the u-joint where the transmission yoke connects to the driveshaft. I have new u-joints already ordered. After some research about the exhaust leak sound, I checked and tightened the bell housing to the engine and the converter to the flywheel. I was able to get a few more turns on all of them. Hopefully, those things will solve my current issues.

My question now is with the Black Friday sales, should I consider ordering a new transmission to go along with the rest of the new driveline?

1. Are there any recommendations as far as certain brands to look at for another 400TH? I’m wanting to stay around $1500.

2. I’ve considered switching to a 700R-4, but I’m concerned with my current set up and how the difference in gearing from 1-2 in the 700R-4 would affect performance. My Chevelle is mainly just a street cruiser and has only been on the interstate once. Future plans for the engine may be EFI conversion, probably not much more as far as power and torque. If I went the 700R-4 route, is it just a swap out and drive? I know I would need a new converter, but is a lockout system required? The overdrive gear would be nice, but not a must.

3. I have considered purchasing a junkyard 400TH and rebuilding it over the winter as a project for myself. I found 2 for sale near me that are $125 and $150. They say they are good cores and both came out of running vehicles, which who really knows if they did. One is a short shaft and the other is a long shaft. Does anyone have an idea price wise if buying one of these and rebuilding it with heavy duty parts and a Transgo kit would be worth it or if buying new would be the better option?

I’m on the fence about which way I want to go and would love to hear everyone’s thoughts and recommendations. I want something strong and reliable enough to handle over 500 hp and 500 ftlbs of torque. I’m just trying to take advantage of any Black Friday/Cyber Monday sales. Thanks in advance and have a great Thanksgiving!
 
See less See more
#2 ·
I'll dive in and reply to question #2 for you - if you don't want/need the overdrive, stick with the TH400. Also, the 700r4 would not be just a drop in - minimally you'll have to move the crossmember and get a different driveshaft, deal with the TV cable setup and then determine if you want lockup or not (and then deal with lockup if you go that route.)

For your other questions - I'm no expert with a TH400 (other than I know you can put a TON of power in front of them and still have them hold together) so I'll leave those to others to answer.
 
#3 ·
:cool: 1. Find a local to you transmission builder. Ask around at Car Shows, ask club members, ask TC members who live near you. Don't buy from a natilnal builder because most (and note that I said "most") of their warrentys require YOU to remove a malfunctioning tranny, and YOU to crate it, and YOU to ship it back to them, and YOU to pay for shipping (see where I'm going with this?). With a local builder the worst case would be your ride gets fowed to their shop.

2. You'll like (nope, I didn't say love) a 200-4R or a 700R4, once it's sorted out.

3. As far as building one youself. Fine, but lots of book learning involved.
 
#4 ·
I usually buy TH400 cores for around $100. Try to find the one you need, in your case a short shaft, but if you can't it's not a huge deal. You can get an output shaft and housing.

I would stick with the TH400. But it doesn't sound like there's anything wrong with yours. You can firm up the shifts a bit by turning the modulator screw in a little. It will move your part throttle shift points up slightly as well. Start with that. Is your kickdown solenoid working? That has a big impact on WOT shift firmness.
 
#5 ·
Thanks for the replies! I really appreciate them. I was leaning towards staying with a 400TH, so you guys sealed the deal for me. I’m sure the 700R-4 would be great, but I like to keep it simple and don’t really need the OD at this time.

As far as the kickdown solenoid, it isn’t even hooked up. I know the PO was building it as a drag car, but I really don’t know a whole lot about the kickdown solenoid. I can see it’s leaking a little bit, but there are no wires going to it let alone it being hooked up. Maybe this is something I should set up? The transmission currently will downshift. Mostly at WOT or when coming to a stop. Please advise me more on this, if you can!

Besides replacing the filter and fluid, is there any other things I can do to freshen it up a little or as preventative maintenance? Concerning whatever shift kit was installed, would it be helpful for me to install one of the Transgo Reprogramming kits? Like I said, I have no clue what shift kit was installed in it.

Is the whistle sound when manually shifting around 3k something to be concerned with or something that may foreshadow an upcoming issue?

I did research a bit and found someone near me that has a little shop and has 35 years experience building transmissions. He charges about $500 in addition to your core for a 400TH. He does advertise that he can build you a transmission with Borg Warner and heavy duty parts for an additional amount. But, after hearing from you guys I may just fix up my current transmission and use my money on a new complete wire harness or some suspension upgrades.

Thanks again for all of your help!
 
#6 ·
After doing some research, I think the kickdown solenoid was not hooked up by the PO because the car originally came with a 350TH. I wasn’t able to find the wiring to the solenoid, so I checked the build sheet that I found under the gas tank and compared it to my Factory Assembly Manual. It came with a M38 transmission, which ends up being a 350TH. After reading a little, the kickdown was attached to the throttle linkage on the 350TH. The 400TH kickdown wiring was attached to the top of the gas pedal. Makes sense why it’s not hooked up and the wiring is missing.

I’m assuming it would be best for me to purchase a kickdown solenoid kit to hook it up in my Chevelle. Sounds like it would really help the downshifting and driveability.

Do you guys think this is something that will be very noticeable after installation? Has not having it hooked up caused any stress to the transmission itself?

Thanks!
 
#7 ·
It hasn't caused any extra stress not having it hooked up but it makes a world of difference in drivability. Get it hooked up and working, adjust your modulator and you'll think you got a new trans. You've done all the maintenance you can do and I wouldn't change anything until you get the kickdown working.
 
  • Like
Reactions: shovelrick
#8 ·
My T400 (RV HD T400) doesn't have an adjustable vacuum modulator so you might have to buy one to do this mod but from my understanding it's a very good improvement to be able to do it. I'd work with what you have since it aint broke :thumbsup:
 
#9 ·
I replaced the vacuum modulator not too long ago and did get an adjustable one. I just never played with the adjustments on it yet. Thanks for thinking of that, though!

I’m going to order the B&M kickdown switch and replace the kickdown solenoid. I’ll change out the filter and gasket while I’m at it. I have a small leak from the tailshaft extension gasket. I may just replace that and the bushing as well. After all of that it should be good to go and I can spend my money on other improvements to her!!

I’m truly grateful for everyone’s help!!! Thanks a lot!!
 
#10 ·
Rear gear's and intended usage has a lot to do wither or not an O/D trans would be of any major benefit.

Your T400 built correctly will take a considerable amount of abuse for a long, long time.

The kick down solenoid is only for passing gear and unimportant for any other trans. functions.
Unlike the throttle cable on a T350, which controls both.

The old ford type F fluid is basically the same as the B&M stuff.

The vacuum modulator controls light throttle upshift points to a degree, while the governor does the full throttle high RPM point.

Not sure about the 3Kwhistle.

For a builder.
Any drag strips locally?
Talk to some people out there.( A common name will start coming up. )

I personally like the T400's.
Been beating on mine on and off track for almost 3 decades now.
 
  • Like
Reactions: Kirk's67SS
#14 ·
If only I still lived in Jersey! I was born and raised there, but after joining to USAF I got stationed in Omaha, NE. Then, got married and had 3 daughters. So, I stayed here. I have good memories of going to Atco and Cecil County Drag Strip in Maryland. I’m from South Jersey. I had an 82 S-10 with a 350 when I was in high school. I thought that thing was the fastest vehicle on the road. Boy, was I young and dumb!!! It was fast among the cars in the high school parking lot. I went to Cecil County expecting to run in the 13’s. Not even close!! My best was like 15.9! It was still
a great time, though. I did win a few street races against fellow classmates in their mom’s minivans!!
 
#12 ·
Do not have a Kickdown/Passing option on my TH400 as it is a good way to ruin/wear out a Trans quicker

the Kickdown is the Trany going from 3rd Gear to 2nd Gear
and therefore the Rpms of the Engine going from say 2,500 to 3,500+ to maintain/increase your Speed is bad

So not only does it produce more stress/wearout on the Trany it also increases wearout on the Engine IMHO

I would never install a 700R4 in my car as the Gearing for 1st is too high & then drops too low to keep the Engine in it's power band

And if I ever go to a OD Trans it will either be a 200-4R or a 4L80 for me
 
#13 ·
So having the kickdown solenoid properly hooked up and functioning is bad for the transmission and engine as opposed to not having it hooked up? I’m just looking for clarification.

Your reason for not wanting a 700R-4 was one of my main concerns about it. I’m going to stick with my 400TH. Thanks for your input! I appreciate it!
 
#15 ·
So having the kickdown solenoid properly hooked up and functioning is bad for the transmission and engine as opposed to not having it hooked up? I’m just looking for clarification.

Your reason for not wanting a 700R-4 was one of my main concerns about it. I’m going to stick with my 400TH. Thanks for your input! I appreciate it!
The TH400 in my car has been in it since I bought it in 2005 and has never had a Kickdown hooked up

Rebuilt it in 2009 because of a bad/loose Torque Converter that burnt it up

Just had it rebuilt, with a Reverse VB / Manual Shifting, again in 2019, after 10 years of Street/Hwy and Track duties/abuse

If you are needing to rebuild it look into stronger than stock parts etc. & the Reverse VB Manual Shifting
it took me a little while to get use to it after 50+ years of regular type Shifting
- Shifts N 123 VS N 321
And the benefits are great
- the Rebuild should last longer as less things to go wrong VS the Auto Shift aspect
- no shifting into Neutral by mistake after 2nd Gear
- no hesitation on each shift from 1st to 2nd to 3rd
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top