Turbo 400 transmission rebuild?

[Steve G.]

I am in the middle of a restoration that started out to be a 'just clean it up and get it running' project. Motor and tranny are out. Body is off. And I am starting to clean up chassis before I paint it...

I have no idea if the transmission worked ok or not as car was not running when I bought it (car sat since 1985 and I was afraid to start it). Previous owner said it ran good in early/mid '80s when he last drove it. I understand Turbo 400's are pretty solid, so I am thinking of just changing front and rear seals and bolting it back in. But have heard a couple people say have it rebuilt just in case. That is another $1000 I'd rather not spend if I don't have too. Do the transmissions go bad from just sitting in garage for 20+ years? Is there any way of checking for signs that something may be wrong? It is the original transmission as VIN is stamped on lower edge of it. Steve

[Jim T.]

Re: Turbo 400 transmission rebuild?

Steve I have a original owner 1970 with the turbo 400.

I have changed the transmission filter and the fluid 4-5 times since it was new.
Removed it, easy to do once and took it to a transmission shop to have new front seal and rear seal installed, it was inexpensive.
I installed a new seal for the shifter rod that goes into the case and installed a new speedometer seal, both easy to do.
Have over 160K on it now and it can literally chirp the tires shifting from first to second like when it was new. Never did this often.
With yours I would only change the filter and fluid and drive it and evalute the performance.
If you want to spend a few bucks go to GM and buy a new transmission oil pan for your turbo 400.
The replacement pan is made of thicker metal and really seals very well. I did this over 20 years ago, no seepage and no leaks from the replacement pan unlike the inferior original transmission pan. Well worth the money in my opinion.
Not knowing the history of the fluid changes on your turbo 400 you could drive it after the fluid change and then change it again. Only changing the fluid and filter will not change the fluid retained in the convertor. I would give it a chance to perform. You will find some "stuff" in the pan, this is normal.
Something else you can do with your trubo 400 is buy the magnet that GM put in later model automatic transmission pans and install it when you change the fluid and filter. I recommend the GM Delco filter if it is still available.
Check up in the tube cavity for the transmission filter to ensure you remove the o-ging gasket on the filter removal if it is not on the filter tube when removed.

[Tom L.]

Re: Turbo 400 transmission rebuild?

I found out that my TH400 was used up about a month after I bought it on the first real cold day of the Fall, all of a sudden the car would not move! A friend told me he rebuilt his own using a B&M transmission kit and it wasn't that bad to do. I decided to give it a try. Directions were great. They outlined everytrhing step by step, even told me when to take a break because I should be getting tired! As scary as it was all went well and it works fine. just take your time and NO beer!!!

[Gary R.]

Re: Turbo 400 transmission rebuild?

Invest in rebuilding it now. It's out of the car. $1000 for a TH400 delivered to a shop is too much. These can be done in a day by an experienced man.
Better yet invest in the good video on rebuilding it, buy a qaulity rebuild kit and new TC and do it at home. Probably cost $450-500.
I made a holder to hold it on my engine stand.
Check this link as well

http://www.digitalcorvettes.com/forums/showthread.php?t=109572

[Steve G.]

Re: Turbo 400 transmission rebuild?

Thanks Gary! When you say buy a new TC - is that torque converter? Aren't those expensive?

The link showed some interesting info. The story about someone rebuilding it and running into trouble makes me think I shouldn't do it. You are probably right - $1000 might be if someone had to take tranny out of the car. If I can find someone experienced to do it for $450, I would pay to have it done right. Steve

[Jim T.]

Re: Turbo 400 transmission rebuild?

Took my 1970 for a ride yesterday. Doing about 30 keeping in second gear on a on ramp to get on I-40 traffic was coming and I punched it, the engine responded rapidly and the turbo shifted down into low and I get onto I-40, about 60 the turbo 400 shifted out of low to second and broke traction real good. The ole GM ZZ1 350/345 crate engine responded really great and the original 39 year old turbo 400 is still impressive.
My son gave me a B&M shift kit back in 1980 for Chrsitmas, still don't think I need it.

[Greg L.]

Re: Turbo 400 transmission rebuild?

Steve,

Since it's already out it wouldn't hurt to go through it just because it's such a bear to get out later if something does fail. The ole 400 isn't really that hard to do if you have some basic mechanical skills, the proper instructions and a couple special tools for compressing the springs on the clutch packs. These special tools can be made without too much trouble especialy if you have a hobby type welder or torch of some kind.

I agree that a grand to do this is WAY too much for a hand delivered trany. If you check around with some local members or even on Craigs list you might find someone willing to do if for a reasonable price. I would think that $200 labour, $300 tops would do it plus a seal kit and clutches(if it needs any).

I did mine last summer and the last one I did before that was about 20 years ago and it was this same trany. The only reason I redid it was because it was out and I wanted to sure that it was going to be okay. One set of clutches were turning dark so I replaced them and I also replaced all the seals just because. For what it's worth they still seemed soft and probably would have been okay had I not taken it apart but like I said, it's a bear to get out so I just wanted a little insurance.

If you want to tackle it yourself feel free to ask me anything and I'll try to help.

[Michael H.]

Re: Turbo 400 transmission rebuild?

I would think that $200 labour, $300 tops would do it plus a seal kit and clutches(if it needs any).

I agree, a grand is outrageous. That's about a six hour job IF you take your time.

[Scott P.]

Re: Turbo 400 transmission rebuild?

Steve, my vote is to pull the pan, check the color, smell and condition of the fluid, tear the filter apart to see if anything is in it, if there is any indication of yuk, rebuild it, if not yuk change filter, speedo seal, shifter shaft seal,vac modulator oring, rear seal, front pump seal, dip stick tube seal, drain out as much of the fluid from the converter as possible (Chevy does show drilling a hole in the converter draining the fluid and pluging the hole with a rivit in some automatics), add the new fluid after instulation and drive away. Turbo 400s are a really good transmission, as you stated.
Scott

[Terry B.]

Re: Turbo 400 transmission rebuild?

Steve,

I was in the same situation as you with the body off and everything off the frame with my '68. There was no doubt that my tranny needed to be rebuilt. I called a few restoration shops to get their recommendations of who should rebuild my Turbo 400. I called the shop that most had recommended, said they could do it for $650 complete if I dropped it off and picked it up. They had it done in less that a week. It sat in the garage for about 2 months while everything else was being completed.

One thing I would do differently is the outside cleaning of the unit. The transmission shop dipped the case in sometype of cleaning solution that took the paint off the lable tag of the transmission. I do not know the other cleaning options but I sure wish I would have not lost the paint on the tag. I still have the stamped numbers however.

I would definitely get the tranmission work done now while the car is apart..

[Steve G.]

Re: Turbo 400 transmission rebuild?

Wow - lots of great information. Thanks guys! If I tackle it myself, I may contact you Greg for some further help. Terry, thanks for pointing out the numbers could come of the tag during cleaning at transmission shop. If I go that route, I will make sure to tell them to not dip it. I have been thinking about cleaning the case myself. I used some Gunk on it, and that got most of the grease and dirt off. But it looks oxidized. I was thinking about polishing it, but then it wouldn't look original. Any suggestion for cleaning it to get the factory look back? Steve

[Dick W.]

Re: Turbo 400 transmission rebuild?

Wet the case with water, spray it with aluminum cleaner, use a wheel brush and scrub the case. Thoroughly rinse with water.

[Steve G.]

Re: Turbo 400 transmission rebuild?

Thanks - I will try that. Steve