question on th400

Hey, I just put a th400 in my 94' Z28 and the problem is that it short shifts from first to second even though hold the shifter in first gear. It has a shift kit and 9.5" coverter.It has an adjustible modulater valve that I've tinkered with no luck. Someone told me that all th400's do this. I've owned th350's that I'm sure didn't. Is there something I can do to stop this besides a new valve body?
I know this ain't classic tech but the trany kinda is and I figured u guys are more familiar with them. Any help would be greatly appreciated.


~Jared

I'm not sure how that could be changed, but I do believe that's common with TH400's.

My friend used to drive a '75 Chevelle Malibu (it was literally his grandpa's car!!!:D) with a 350 and a TH400, and that car could not be held in 1st gear with the shifter --- regardless, it shifted to 2nd. My '81 Z28 with a TH350 however, would stay in 1st gear if I held it there........so it's obviously "normal" for a TH400.

If you took it to a tranny shop though, they may be able to tell you how to change that??:confused: (sorry I can't help ya with that?!:()

Yeah, I talked to a few people and they all said it's normal and that the only fix is a manual valve body or a B&M transpak.Looks like I'll be forking out more dough :cry: Thanks, Jared.

What kind of shift kit did you use? I used a transgo in mine and have no problem holding gears. You can set it up manual or auto shift.

It has a trans go, but I bought the transmission with it already installed from a buddy...Hmmmm.....I wonder if he still has the rest of the kit. I'll give him a holler. Thanks alot!!

I cannot remember the exact modification, but I rebuilt mine like years ago and fixed that problem. It seems like I took a particular valve and ground a flat spot on one side of it. Of course, there were holes to plug and check balls to remove, too. I think it took a couple of mods to the valve body to correct that early shift point. Anyway, I had a book that had an article on TH400 mods, and it told how to set one up for street performance or even hard-banging strip perfomance. I wish I still had that book. It was great, but it disappeared a long time ago, probably loaned out and never returned. The mod definitely made a difference, and the other stuff made shift hard under acceleration. I bet if you did some searching on the internet, you might find some info, maybe by trying "TH400 tips," "TH400 mods," "TH400 shift points" or something along those lines.

Wish I could give you some more specific help. It's just been too long ago, like 1985. It's starting to leak pretty bad, so I may be doing a reseal job on it before long. Actually, I'll probably just replace it with a T-56 or one of the automatic overdrives.

Good luck!
Bill B.

Additional info: Here's a link that might be helpful. Without some real specific information, your best bet may be to buy a good shift kit from B&M or TransGo, etc. Check this link...

http://www.camaros.net/forum/Forum9/HTML/003594.html

Thanks Bill, I've searched the web high and low with no luck.Guess I'll just order the goofy kit LOL.

Yeah, I did some searching myself and came up with nothing more than fixing it with a shift kit. I wish I could find that article, but it was a long time ago. It was a little more work than putting in a shift kit, but I think it did essentially the same thing. I remember grinding on a valve from the valve body and plugging a hole. Other than that, it was not a whole lot more. I guess I'd have to do the shift kit myself these days. Anyway, good luck with it.

Take Care!
Bill B.