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TH350 rebuild

E

ed rex

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Penn Valley, CA
So, the TH350 in my '70 Jimmy is pretty much toast. Looked into replacing with a TH400 but not sure that I want to deal with all the 'fit-up' as well as the loss of HP. Most of the local tranny shops will rebuild for about $500 - $600.......that's with me removing, dragging in and then re-installing.

With that in mind, I'm starting to think why not just go for it myself? Get the hi perform/HD kit and a 'do-it-yourself' video from say JCW and dive in. That way I'd be learning something as well. Naturally, the ads for the video make it seem like a simple operation. Have any of you attempted this route? Any special considerations I should be aware of? I consider myself to be rather handy in the garage. About the only thing I haven't done on that truck is the inside of the tranny.

What do ya think?? Go for it?? Or is this a not no but HELL NO situation?

Thanks
 
I'm considered rebuilding my TH350 too but decided that I really don't know enough or have enough time to deal with it. I did go to the library and noticed several books on rebuilding the TH350. You might check out one of those books and see if it is a reasonable undertaking. From what I heard, the TH350 is one of the hardest trannys to learn how to rebuild for your first one. For just a little more than the shops rebuild price, you could probably pick up a remanufactured TH350 with a nice warranty. You'd still be removing & installing it though.

'69 K-5/350/TH350/35's & 6" Lift
 
I bought a good book and did mine myself about 75k miles ago and it's going strong. Wasnt really hard, only new tools I remember getting were bushing drivers. Used all the best parts and was still much cheaper than generic rebuild by tranny shops. When I was in the middle of it, I stopped by a shop looking for different thickness spacers to set the gap in the clutch packs and they said they were all the same, I went through their junk pile with my calipers and found what I needed. Turns out the guys at that shop were idiots, glad I didnt listen to them. I guess it comes down to who you trust and how much time you have to spend.
 
I bought the B&M transkit for my TH350 rebuild for a little less than $200. It has a good manual for someone who has never done this kind of work before. Actually a TH350 is one of the easier trannys to learn to rebuild according to my local trans shop. There are a couple special tools you will need, but they can be fashioned at home if you have some steel strips and some long bolts (to compress the clutch springs), or you can rent the tools. I did it with no previous experience, and recommend the B&M product. I can give more details if needed. See ya, JT
 
Naturally all of us would love to see a bunch of digital pictures of the rebuild!!! I am sure they always welcome tech articles on the main page.

Just to throw a possibiltiy into the works, I saw an article a couple years ago about a rebuild kit that eliminated 'something like a clutch?' in the auto tranny. It also added an overdrive as well? I think it was in 4wheeler mag if I remember right.

Basically the reason I was asking about it, supposedly it made for a much stronger transmission. As you can tell I am an accountant, not mechanic so the details are a bit fuzzy. Anyone know of the rebuild kits that BEEF up the tranny while you are in there?

My transmission needs rebuilding as well, 72, automatic so I think I will be in same boat! Let me know how all goes!
 
The nice thing about the B&M kit is that you can dial in the shift firmness in three stages by performing different mods while you are in there. There are drawings included to have the clutch pistons machined to accept additional clutch discs which increase the torque capacity of the tranny. Additionally you will remove certain springs and check balls to give a more positive shift. Very quick and firm but not harsh. Along with the B&M Holeshot 2000 torque converter, this set-up has been more perfect than I imagined. JT
 
That's good to know about the B&M kit. My Blazer has been sitting in the driveway since August waiting for the $ to get a new tranny. Now, I'm considering the B&M Kit. The tranny now has a shift kit (don't know what stage but I'm guessing stage 2) but the shift is way too hard and clunks the whole truck. If I rebuild, I'll go with a kit with a little less harshness in the shift.

Let us know if you rebuild. Also let us know if you buy one of the JCW videos. I'd be interested if they are worth it.


'69 K-5/350/TH350/35's & 6" Lift
 
Sounds like the B&M is the way to go.

JT - what kit exactly did you purchase from where?

Thanks! Ed
 
I'm in the middle of a FOR and once my 383 is buttoned up and my garage can be kept clean for a few weeks (important), I'll tackle the TH350. The local transmission guy said the TH350 is the simplest (vs. Honda - very difficult) and he suggested using the GM overhaul book (which he let me photo-copy) since it has high definition pictures. He also offered his press for some of the clutch mechanisms. So I went from thinking 700R4 ($1800) to overhaul ($500) to DIY ($180) with some confidence. I can hardly wait!

Once I dissassemble the tranny, I look for wear, pitting, etc. then determine the parts list (vs. buying a generic kit). The guy also liked a non-B&M vendor (I forgot for the moment) for replacement parts (I'll worry about that when the time comes). Mine already has a shift kit in it, so I don't know if I'll need to do anything there.

The main goal was to beef it up for the increase in torque from the 383. I'm not sure of your timetable, but I can document the steps I took and report back, if you guys are patient...
 
I built the TH350 in my Suburban. The only specialty tool that I used was a clutch spring compressor. I bought the rebuild kit at NAPA and the Tran-Scat Super II shift kit through JEGS. I used a Haynes GM transmission manual. It is full of pictures and was a lifesaver throughout the process. After teardown I found that the case under the valve body was chunked and I ended up replacing the case with a used one. It took a buddy and me about 2 days to remove, rebuild, and replace. It has been running strong for a year and a half behind my healthy 388 stroker.
 
When you replaced the case did you get a 4X4 case or a 2X4 case???
The reason I ask is I had my tranny rebuilt almost 3 years ago, and the first case was cracked so I had to get a new one... I just recently found out that it's a 2X4 case. I was steaming when I found out. The 4X4 cases are supposed to be a little stronger because the flange is about twice the thickness on the front of the tranny, and there are 4 drilled and tapped holes in the 4X4 case that are not there in a 2X4 case.
It's too late to do anything about it now, but I went back and fu%kin' b!tched out the dude asking him if it is common for them to replace 4X4 tranny's with a 2X4 case!?!???
You'd think there's a reason why there are 4X4 cases for 4X4's huh!
I'm looking for spare 4X4 cases... but I've seen 2X4 cases on other 4by trucks!?

[Real Men Don't Care About Gas Mileage Or Rapid Tire Wear!]
Ryan B.
 
Ed rex, I purchased the "B&amp;M Transkit" for 68-81 TH350 (part number 30229). I got mine from <a target="_blank" href=http://www.PAWinc.com>www.PAWinc.com</a> for 192.00. I'm sure Summit Racing also sells it. I also bought the B&amp;M deep trans pan for extra capacity and the B&amp;M Holeshot 2000 torque converter. Good luck. JT
 
The tranny I bought was a 2wd tranny. I tore the tailshaft housing and all of the guts out and put the guts from my Suburban tranny in it. I compared the cases and noticed no differences. No problems with cracks or anything so far and I wheel her pretty often

1971 GMC Suburban K1500
388 CID SB Stroker
4" Rough Country Lift
32" BFG MT's
 
Thanks all for the advice. I am currently in the final stages of swapping out the front end. Just a couple of brake lines to refit and she's back up. Then I'll be looking at tackling the tranny. Gonna order up the material directly so's it should be here by the time I'm ready. I'll keep you all posted.
 
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