OldsManNJ

I am in need of a new TH350 for my 71 Daily Driver. My motor is a mild rebuild making about 325HP so I don't need anything crazy as it is a daily driver. there are so many places that sell rebuilt TH350's though I don't know where to start and I have a few questions I am unclear on. I am hoping one or several of you tranny gurus can voice your opinions for me.

First - I see them listed as manual or automatic - I am assuming that means the shifting mechanism? So an auto you can put the tranny in Drive and go - or you can shift manually with it - a manual shifting would be that only - there is no Drive and go? Is this correct? I also see a lot of them state that they do not work with a kick-down? Why would they not have the kick-down option?

Now the tough part - there are so many places that sell transmissions - I have no idea who makes quality and who doesn't - I see them ranging in price from about $600 to up over 1200 - can someone recommend a quality unit for me to buy? Summit, Jegs, Monster, etc - too many choices. I would also like to change out the Torque Convertor at the same time as the trans - so my next question is - What convertor do I want to use with my setup?

My budget for this project is $1200 and I will do the work myself with friends, so I can spend that whole amount basically on the parts.

I really appreciate the time anyone takes to read and reply to this - the amount of knowledge here is extremely valuable and I appreciate your time.

oddball

It's been too long since I built mine, so I can't help with sourcing. Although my opinion is the TH350 has been around long enough and basically unchanged that there's not much to screw up. Any reputable build should be OK. I'm pretty certain my current torque converter is a TCI Saturday Night Special. That was behind a mild 350 with 2.73 rear end and worked really well. Picking the right torque converter would require knowing your camshaft and rear end specs.

The variants that you're seeing are for drag cars. A manual valve body means it goes into the gear you select - and that's it. So D is really 3rd, even if you're stopped. There's also reverse-manual where D is actually 1st and 1st is actually 3rd.
Same thing for the kickdown - you don't want that messing with the valve body calibration when going down the track.

For a driver, you don't need - or want - any of that.

I have a deep appreciation for the TransGo stage 2 shift kit, so I'd look for a tranny with that already in it. Similarly, I didn't enjoy the B&M shift kit very much. There are opinions both ways.

You can probably get one cheaper by calling up local transmission shops. Installing the shift kit yourself is very easy, especially out of the car!

matt69olds

If a shift kit is advertised as a auto/manual, that means if you leave the shifter in drive, it will shift 1-2-3 just like stock. It will downshift to any gear at any speed, and will HOLD any gear at any speed. Most stock valve bodies will upshift at a certain speed, regardless of what gear the shifter is in. I'm guessing that was designed into the valve body calibration to prevent warranty claims for blown up engines.

If the valve body is advertised as a manual, that means there are no automatic features. The trans is in whatever gear the shifter is in, without regard to vehicle speed. There are also reverse pattern manual valve bodies, they were originally designed so you upshift the shifter away from neutral and more importantly reverse gear. With modern ratchet style shifters hat isn't much of a concern anymore.

To answer your question, I'm pretty sure every shift kit made for the TH350 trans includes the "dual feed" transfer plate for the direct clutch. For some silly reason, GM designed their transmissions with a direct clutch that is split into to chambers, 1 for third gear, and uses both chambers for reverse. Its real easy on a TH350 to combine both chambers with the use of the transfer plate for third gear, this doubles the torque capacity in third gear. Its even easier to do the dual feed modification during a overhaul. All that is required is a small freeze plug (used in the TH400 trans) or a small setscrew (used in the TH350 trans) and leaving out the sealing ring or lip seal that separates the 2 chambers. There are no compromises doing this modifications. I have ask lots of professional trans builders why GM did this, nobody has a good reason. Seems to me its a lot of unnecessary extra hydraulics and machining.

The B&M Transpak and Trans-Go shift kits are the best in my opinion. The B&M is cheaper, but makes the shifts really firm at part throttle due to the bigger orifices and deleting the accumulator functions. I like this shift kit if your using a loose torque converter, the higher stall speed absorbs a lot of the shock out of the upshifts. The Trans-Go kits are more refined, they leave the accumulators functional so they shift smoother at part throttle. Due to the extra parts needed to recalibrate the accumulators they are a littler more expensive. Either kit can be installed in the garage with the trans still in the car. If the trans is in good condition and you would like a firmer shift then either of these kits will work well.

If your looking for a NEW transmission the TH350 is about the easiest trans to build. I walked my 13 year old step-daughter thru building one years ago. There are few special tools needed to build one, what is required is pretty cheap to buy or fabricate. If that more than you want to tackle then any transmission shop can rebuild one. They are very durable transmissions.

OldsManNJ

Thanks for the responses Matt & Oddball - I appreciate it. Since this is my daily driver and it is still driving right now (but slipping worse every day) - I really need to buy a new trans and put it in over a weekend as I need my car for work. I wouldn't be able to take it to a trans shop and have them rebuild it and keep it for a week or so.

I would like to buy one with a shift kit in it and a new torque convertor, but I don't know who's to buy or which convertor to get (How many RPM's). I am ready to order it as soon as I figure out who's to buy.

oddball

If you haven't done much to the engine, then keep the stall around 2000 or less. Wild cams need the high stall, but it's a PITA around town.

Matt's info is excellent! Although I did a TH350 rebuild myself, and that's now on my list of things not to do. Having the proper tools would've helped a lot, though. Unfortunately the pump ended up exploding. The shop said it was slightly out of spec and would've been impossible for me to know anyway.

Several tranny shops will stock common units like a TH350 - just make sure to get a universal bellhousing or a BOP-specific one if you can. I can't remember if the TH350 came in chevy-only or if all the chevy ones were universal.
Anyway, you can probably walk out with a rebuilt unit and haul in your busted one whenever to get a core deposit back.
IMO, it's not worth getting a high-spec aftermarket unit for where you are at right now.