Hot Rods First time installing a TH350

Hello guys. I bought a Studebaker with a 406/TH350 setup. The seller had already ripped up the last TH350. Now, in the car, is a standard TH350 that he installed. 1st acts like a brake; 2nd goes forward but no different than Drive (as though they are the same). I was thinking of acquiring a good used transmission and removing the old. I am not going to hammer this car. Cruise only. The engine feels very powerful as if it has 500 + horses. Any suggestions as to a tranny and how I should install it. I have $700 budget (currently) for the used tranny. Thanks.

 

I'm not really understanding your post.

Are you telling us that the trans that's in it is a TH350 with a first gear that acts like a brake and a 2nd that works like D, which would be the second TH350 that's been in this car, and now you're looking for a third?

If the engine is as powerful as you say it is, and it keeps lunching TH350s, you either need a stronger TH350, or a TH400. Neither of which is going to be available for $700. A TCI Streetfighter would probably be up to the task, but you're not getting that within your budget. And frankly, unless I know the history, or I am willing to take a chance that it doesn't work at all, I consider every used trans to be a core.

 

Maybe look at having yours gone through with some performance upgrades? Might stay near your budget, I don’t know for sure.

 

maybe consider a 700R4 or 4L60E. that would also give you an overdrive.

 

Price a rebuilt one, from a rebuilder. That will give you a warranty, and will be as good as most used ones you will find, and would be well worth the extra dollars.

 

Well the former owner abused both transmissions and the car. The vehicle had brand new 375 tires on the rear $500 a piece) and he peeled out in it so often the right rear tire is bald.

There is a transmission guy sort of by me in Oregon who has a used built TH350 for $750 plus core. I know him to be reliable so I'm not worried about that. I really am looking at guidance pertaining to de-install and install of a replacement TH350, or, a TH400 upgrade. Thanks.

 

Would a 700R4 require a different driveshaft because of any size difference compared to the TH350?

 

I do have the other transmission. The seller claimed the internals were all hardened and that he was planning to "swap the guts" into another housing.

 

you could learn how to build 350 transmissions, and probably make one that would live for a while. But if you just want to know the procedure to Remove & Reinstall a TH350, we can help you with that.

You need to get the car up in the air high enough to be able to lower the transmission, and it needs to be well supported...so you need good quality, big jack stands, or else cribbing blocks under the tires, and a way to get the car onto them. Or a lift, if you have access to one.

Then you probably want to drain the transmission, do this either with the drain plug, or if it's like most and doesn't have one, drop the pan part way down, let it drain, and bolt the pan back on. You need a big drain pan for this, I use a restaurant bussing tub.

Then disconnect the stuff connecting to the transmissions, such as the kickdown cable (do this at the top end for now), shift linkage, cooler lines, vacuum line, speedo cable, and remove the driveshaft. Remove the cover under the torque converter, and remove the 3 bolts holding the converter to the flexplate, you'll have to rotate the engine to do this. Then support the transmission with a transmission jack, remove the crossmember and the bellhousing bolts, and lower the transmission.

When you get ready to install, let us know, and we'll tell you the tricks about the kickdown cable, getting the torque converter in all the way, etc.

 

There shouldn't be anything too difficult in removing and replacing a th350, the bellhousing bolts will probably be the most difficult thing, perhaps the cooler lines also, and the kickdown cable is not an actual necessity. Keep your shifter piece and all should be a relative piece of cake.

 

If he's having problems with longevity with a TH350, it makes zero sense to switch to a weaker transmission. The OD is great, but that TV cable is difficult and these transmissions are not meant for high HP applications. If OD in an automatic is necessary with that much HP, then 4L80E or GearVendors is about the only option.

I agree with the other here that a simple remove and reinstall is easy enough, with the reinstall being essentially the reverse of the former. Getting the torque converter all the way in can be a bit tricky, but that's really about it. You also don't need to run a TH350 with a lockdown, though you can. The only thing you need is a vacuum modulator, which is almost impossible to screw up.

The only other comment I'd make is with the TH350, if you do wind up sourcing a new trans, make sure the tail shaft is the same length or the driveshaft is not going to fit. They came in 3 varieties.

 

Just get a rebuilt TH400 and be done with it. They will handle the HP and last a very long time.

 

Well, I don’t know what I’d be looking at tearing an automatic apart, if you plan to swap the parts over, get a good manual to show you what to check/etc

 

The problem I see with this is that the op doesn't sound very knowledgeable so he probably wouldn't know what are "good" parts and what are "bad" parts once he gets it torn down...

With the amount of experience he sounds to have I'd just suggest having a good one built or just buy one....


...

 

Are you sure the shifter is set up correctly?

 

Yes, that was why I suggested a manual, I’ve never opened up an automatic (yes, I have miniature balls about some things).

 

The TH350 is one of the easier ones to rebuild, but you do need to know what to look for when inspecting parts.

There are good aftermarket books available. The factory shop manuals don't really give you the little tricky insights that are nice to know, about what parts usually wear in what ways, etc. They are good for disassembly/reassembly instructions.

 

Hey Jim, do you have a suggestion on a book/manual to follow?

 

I don't have a book on that one, but I do have the Ron Sessions book on the 400, which is helpful.

The factory shop manual from Chevy, I have for a few different years of cars/trucks.

 

I think Cliff Rugles wrote one for CarTech on T-350s. If so, it will be good and I think Ron Sessions did one too. I have one downstairs; I'll check back if it is not by Ron Sessions.

 

Before you get too far out there, have someone with maybe a bit more experience have a look at your set up and make sure everything related to the trans is operating properly, like the shifter and modulator valve. Once you are sure you need a transmission, then figure out how to best spend your money.

Good luck and keep us posted.

-Abone.

 

One thing to remember is keep the torque convertor with the transmission. Do not leave the convertor bolted up and try to slide the transmission out. If you need to tilt the transmission forward to get it out, be sure and have something keeping the convertor from sliding forward. If it happens to come out, you will have a mess as it will dump a bunch of fluid.

When installing the new transmission, be sure the convertor is all the way in. It takes some jiggling and turning to get it to bottom. When it is all the way in, you won't be able to get your fingers behind the convertor at the top of the case. If your finger will fit, the convertor isn't fully engaged.

 

Oh yes, a good 350 is a fairly stout transmission. I built a couple for a guy who went mud bogging in a 4X4 Chevy. I didn't do anything special and he was happy. The second transmission I built was a for a spare.

If you happen to decide to try and rebuild a 350, take a good look at the end of the input shaft where it mates into the output shaft. The lubricating oil for the gear train is sent through the input shaft into the output shaft. If the end of the shaft or the bushing is damaged, the gear train will get little to no lube. It was a common failure on abused 350's.

 

Uh, "internals all hardened", unless its racing stuff, (high dollar components) its not likley.

A very good quality rebuilt Turbo 350, with OE internals, a hardened intermediate race, brand name reprograming kit, preferbly a trans from 1976-1979, which has needle thrust bearings between components instead of brass thrust washers and a high quality torque converter, and that the trans does not have a bunch of high dollar racing internals in it, are good for about 400 lbft. of torque.
Torque is what kill the trans, HP is kinda irrelevant.

Some of the things that will kill automatic transmissions is, poor quality rebuild (just because they say its rebuilt, be aware, all rebuilds are not created equal), a loose nut behind the steering wheel, and a car that hooks hard off the line (like a drag strip start), pulling a zillion pound trailer or a mega heavy car or truck.
If the car hooks well, the torque capacity of the trans can be easily exceeded.
If the car just fries the tires on a launch, the trans will really never see the actual torque output the engine is capable of, due to the torque is lost in the spinning of the tires.

I have built many HP Turbo 350s over the years, that have survive for years, provided the car is not driven by an animal.

If you are going to beat on the car, I would recommend going to a turbo 400, built the same way.
Many do not like the deep 1st gear ratio of a 700R4 overdrive and the shift feel.
Yes there are custom ratio planetaries available and hardened (race type) components, but it can get real expensive, real fast.

Bill

 

Might also add to support the back of engine, under the pan, to prevent it from dropping down.

 

The Cliff Ruggles TH350 book is where it is at.

I recently replaced mine, as it was covered in red fingerprints.

 

First, forget anything the bozo told you, lose his phone number (he more than likely won't be calling you), and like prior advice, pay a professional his price, swap yours as a core, get a (written) warranty and be done with it...........it's football season!

 

Bring the car / ship the trans down here...there are a few old
School awesome guys around here that will make sure things are done correctly.

If you want to tackle a transmission rebuild yourself.... my uncle and my dad had a transmission shop when I was a little kid, they would always say the turbo 350 and 400 are easy to rebuild.

What ever you do, DO NOT buy a second hand transmission and expect it to hold up.
Unless you are spending $100 not $700+

 

Plenty of rebuilds on Craigslist, about 650-750 bucks. Most built by tranny guys moonlight ing. If you can get one from a guy you can trust, with a warranty, go for it. If yous is fragged, a new converter is a must. It sounds like the previous owner may have put a you tube shift kit in it wrong. It may be worth it to have it checked out before condemning it. There good transmissions, I've run them behind big blocks, but like anything, if abused to much, can break. Fortunately for me, the weak point in my truck was the rear end, and driveshaft.

 

Hang a clutch pedal and put a 4 speed in it... Problem solved!