is it a big job to rebuild a th350?

Supposedly, it should not be a big job, and should be a straighforward process. I have done brand F C4's and C6's. My current toy runs high 12's with my homebuilt C4 in it, and has for 5 years or more.

I would buy and read a decent rebuild manual before starting, there is a good one out on the TH350, and the ATSG manuals are good to have.

You will need snap ring pliers, and it helps to have two slide hammers to pull the pump.

I bought a clutch compressor tool for the clutch packs and a seal installer kit. Both can be faked or worked around if you have to.

Bag and label every part, nut, bolt, screw, clip, and check ball.

Keep it very clean and go for it.

http://www.carcraft.com/projectbuild/116_9508_th350_automatic_transmission_rebuild_buil dup/index.html

how much should it cost to have one rebuilt? just curious

They are actually one of the easiest transmissions to overhaul. Get a manual and have at it.

what else would you do to one if you wanted to modify it? what is the purpose of a valve body or trans brake?

Find this book at your local speed shop or most bookstores. It'll answer all your questions.

http://www.eautoworks.com/product-HP-Books-309494.htm

That's the book I used to rebuild one and It's a good one. It has some performance mods too. A TH350 is probably simple compared to some other trans, especially OD's, but it's not a 2 hour job for a first timer. They are still complicated and a lot of parts. It will take several hours. Even though the book is good you must make sketches and notes as you disassemble or you'll be lost at some points when reassembling. As mentioned there are a couple of special tools you'll need to buy or fab. You can get parts at very reasonable prices from www.bulkpart.com (http://www.bulkpart.com).

Now I have been searching salvage yards and calling tranny shops for info. one salvage yard has a rebuilt th350 you can eat off eat in his words. Will that be fine for my car a 66 chevelle and i am having a small block 350 rebuilt cam and internals not known at this time. can a th350 say stock rebuilt handle i dont know 350 hp.and what kind of torque converter is needed. any thoughts greatly appreciated:confused:

th350's are easy I rebuilt mine for my senior project. If you have all the tools it's a breeze. Definatly get in touch with a reputable tranny shop.

as for upgrades, go with a hardened intermediate race, either a 36 element sprag or a new one. Get a transgo shift kit and drill out a couple holes (you can find them on the internet) I wanted a transbrake in my 350 but the gentlemen that helped me said a 350 with a brake is like a ticking time bomb, it;s only a matter of time. If you want a brake go with a 400 or powerglide.

th350 if built right can also handle a lot of abuse. I have one behind my 400+ horse 408 now and will run the same tranny behind my 650+ solid roller 461 here next season.

Another good upgrade to do is install the late 700R4, or 4L60E, low/reverse center support/sprag setup. It will handle the torque on take-off alot better than the stock narrow sprag that comes in the 350. 350's are getting rare, and we only build maybe one or two a year anymore. The parts are also getting expensive, they quit making a non lockup 350 in 79, so the newest ones are almost 30 years old. I usually get around $1000 bucks to build one, if your core isn't too worn out. Do as Paul said, and use a Transgo shift kit, not only for crisper shifts, but for the technical information that is included in the kit. For your parts, I use Transtar, you can PM me, and I give you the # to my salesman and get you hooked up.

i am now thinking of buying a new one from summit. they have one that is good for 450 hp for $659. i cant see buying on from a junk yard for $200 and it needing to be built for $500-$1000. ifound one tday at a junk yard already rebuilt for $400 but can you trust it. i think the smart thing to do is buy new.

i am now thinking of buying a new one from summit. they have one that is good for 450 hp for $659. i cant see buying on from a junk yard for $200 and it needing to be built for $500-$1000. ifound one tday at a junk yard already rebuilt for $400 but can you trust it. i think the smart thing to do is buy new.

I totally agree with you. Even if you try to build it yourself, you'll end up spending money on tools, then it may not work, then you'll just be throwing money away.

is it a big job to rebuild a th350?
You will need the correct tools to compress the low/reverse clutch springs and the proper bushing tools. There is a small bushing that requires a self tapping adapter that screws inside it and then a slide hammer to remove it. Likewise its a BITCH to install that bushing correctly without the proper tool.


jim

You will need the correct tools to compress the low/reverse clutch springs and the proper bushing tools. There is a small bushing that requires a self tapping adapter that screws inside it and then a slide hammer to remove it. Likewise its a BITCH to install that bushing correctly without the proper tool.


jim

Jim that bushing that you are talking about is in the front of the mainshaft, and supports the rear of the input shaft, there is a plastic bushing available for this, that just pushes in easily, also it doesn't wear the tit out on the input shaft as bad.

Jim that bushing that you are talking about is in the front of the mainshaft, and supports the rear of the input shaft, there is a plastic bushing available for this, that just pushes in easily, also it doesn't wear the tit out on the input shaft as bad.
Yeah I remember those. If you ever have any bushing and/or convertor wear (and you will) that nylon gets impregnated with metal and wears pretty quickly.

I recall back in the 70s..........a few cars came into the Chevy dealer that I worked at with trans problems...after dissassembly I found bushings actually melted along with the shift cable and detent cable. The electrical system (ground cable) had lost ground and was grounding through the trans. That was weird...and costly for the customer...built a few because of that.

Showing my age...walked to and from school barefoot up hill both ways.

how much should it cost to have one rebuilt? just curious

I was just quoted $450 for a performance rebuild on my TH350. All Kevlar clutches. Another $150 if I want them to pull it out and reinstall it.

Kevlar clutches??

Yeah I remember those. If you ever have any bushing and/or convertor wear (and you will) that nylon gets impregnated with metal and wears pretty quickly.



Jim,
The other Jim, from the posts I've read of his, know's his stuff. The nylon is the way to go, it can live with less lube than the regular bushing and as he said doesn't wear.

Good tips here. I have an article on Hotrodders.com on some rebuild tips.

A $450 rebuild is a farce. Sorry, but if it's done properly, it will cost more than $450 to rebuild a TH350.
Kevlar clutches are the sign of a builder who just throws whatever the part of the week is at it and hopes it lives.
A TH350 will live to the point of hard parts failure (~800 HP) with stock tan clutches. The Alto Reds are a good choice too but unnecessary.

A $450 rebuild is a farce. Sorry, but if it's done properly, it will cost more than $450 to rebuild a TH350.
Kevlar clutches are the sign of a builder who just throws whatever the part of the week is at it and hopes it lives.
A TH350 will live to the point of hard parts failure (~800 HP) with stock tan clutches. The Alto Reds are a good choice too but unnecessary.


Hmm. I spent $85 on a rebuild kit (stock parts) for one in my old '79 K/10 4x4. It went 25k miles just fine with 35" tires and 3.07 gears before I sold the truck, and the new owner drove it daily loaded down with materials and tools for a couple more years before he sold it. He built rock walls and did concrete work, and usually had a trailer behind the truck hauling a yard or two of concrete materials. In short, that trans lived a hard life, but it lived, none the less. Are you saying you'd need to upgrade the hard parts? Or is the guy not charging enough labor?

I agree it's the " way to go" for ease of assembly but....if your going to lean on it I wouldn't use a nylon bushing if it were mine.

The bushings were used by GM to reduce the need for additional work/machining.
I've seen them melt under hard use, impregnate with metalic particles due to normal convertor/bushing wear. That set up premature wear and failures.

The other Jim does know his stuff...

this jim

Hmm. I spent $85 on a rebuild kit (stock parts) for one in my old '79 K/10 4x4. It went 25k miles just fine with 35" tires and 3.07 gears before I sold the truck, and the new owner drove it daily loaded down with materials and tools for a couple more years before he sold it. He built rock walls and did concrete work, and usually had a trailer behind the truck hauling a yard or two of concrete materials. In short, that trans lived a hard life, but it lived, none the less. Are you saying you'd need to upgrade the hard parts? Or is the guy not charging enough labor?

Yes,
I can buy a "master kit" for $80 but that doesn't include a new band, all new bushings (a TH350 WILL need them), thrust washers (likely to need these), a modulator, a filter, etc...

Nor does it include a hardened intermediate sprag race ($50 in the aftermarket), a new intermediate roller clutch (should be replaced on rebuild, especially on a 350), a case saver, pump gears that are often needed, any type of valve body kit, etc.

You can easily get $300 tied up into parts for a TH350 and that's assuming you have a good core, and 2 out of 3 are not good cores anymore (conservative estimate). Many of my peers feel like it takes about 4 cores to make one good one. At $65 a core my cost, you see where this is going pretty quick.

Plus shop costs.
Cleaning materials and electric to run a wash cabinet and any other shop overhead.

Anybody that is rebuilding Th350's for $450 as a professional business is cutting corners somewhere.

The Kevlar clutches should be enough indication to run away.

I agree it's the " way to go" for ease of assembly but....if your going to lean on it I wouldn't use a nylon bushing if it were mine.

The bushings were used by GM to reduce the need for additional work/machining.
I've seen them melt under hard use, impregnate with metalic particles due to normal convertor/bushing wear. That set up premature wear and failures.

The other Jim does know his stuff...

this jim

I'm not speaking from an ease of assembly standpoint.
I've seen a few hundred come apart with both styles.
I used to feel that nylon thrust washers and in this case bushings were the OEM's way of being cheap but there is a reason for them and they work well.

I'm not speaking from an ease of assembly standpoint.
I've seen a few hundred come apart with both styles.
I used to feel that nylon thrust washers and in this case bushings were the OEM's way of being cheap but there is a reason for them and they work well.
I hear ya. You built many?

I guess that my point of view stems from building them at a Chevy dealer from 1976 through 1981. Everything was built pretty junky back in those days. They cut corners in those days by way of not fully maching the intermediate shafts and using nylon.....all the PGs, 350s, 400s that I overhauled back in those days don't count today for trans assembly 101 today.

I stand corrected.

Thanks,

this jim

Jim,
I've built those few hundred that I said I've seen come apart. I've been building trans for 15 yrs mostly part time but ran my own shop awhile back until I took off to Iraq a year ago.

I have a TH350 to teardown tomorrow. I make the upgraded intermediate sprag/drum setups that use a 36 element sprag. I've built TH350's for 650+ HP/TQ applications and also 240+ mph Bonneville Salt Flats cars. I would say they are getting "leaned on".

I'm not trying to discount your experience, and I built them with the bronze bushings until a couple of years ago. I can install the bronze bushing just as fast as the nylon, so it makes no difference to me. The nylon is actually an additional cost item for me since it doesn't come in the bushing kits I use, so I order them seperately about 25 at a time.

I made a tool to install the bronze bushings from an air hose fitting. It fits perfectly and drives to the perfect depth everytime, and it's quick.

Nylon will run with less lube is the key benefit, and it has good wear characteristics.

Most of the bronze ones I see come out worn to nothing, which creates a big lube loss to the rear planets.
The nylon seems to come out in better shape USUALLY.

In either case,
it's important to be sure the pilot on the input shaft that fits in the bushing is as smooth as possible.

Jake

I wish you lived closer...I'd have you build one for me.

I have a feeling I'll get tired of swapping gears with the Super T-10.

I LOST all of my trans tools from way back when....the air hose deal is great.

Do you have photo?

Did you ever tear one down that did not have the anti-clunk spring?

It ruins the case...the turbo-hydramatic plant actually left some out way back in the day.

jim

Pic of the bushing installer I made from a air fitting?
I can get one. I just ground the tip off a normal automotive quick connect air hose fitting to the proper length.


The anti-clunk spring... I've never torn one down that I know was original without it.
That is the main reason why the cores are no good, even with the anti-clunk spring, the low support moves around in the case ruining it.

If it's a little worn, I install the normal case saver and go. On some cases I have used the 700 low support with the bolt on case saver. You install the support, then snap ring, then bolt on a piece that grabs the case on a new section of the splines.
Half the cases I see are just too far gone and I won't use them.

TH350's have almost gotten to be more trouble than they are worth. I'm going to have to start charging $200 core charge for them because of the bad cases and pumps, planets, sun shells, etc.

The biggests problem is it's been over 20 yrs since they were produced and there isn't a new trans that has many interchangeable parts like there is for the TH400.
They've all been rebuilt, some of them numerous times, and they all have a gazillion miles on the parts.

Jake

Didn't know there was such a thing as a case saver.

could have used em way back when.

Thanks for the conversation.

I reckon we-I hi-jacked the original post.

For that I apologize.

Thanks again Jake.

jim

I'm with Jake on someone who say's that they can build a 350 for $450. There just isn't anyway to build one right for that money. Like I said, I generally charge around a $1000 to build one, and I'm still not making a decent profit, considering the amount of time it takes to round up all the parts, and repair all of the stripped out bolt holes etc. I usually make several trips back & forth to the misc. parts room to find enough parts to build one. I remember when I could buy a rebuilt pump for $12.50, now if I can find one, it's going to cost me $75, then both planetary's are usually worn out, not to mention, it's probably been built before a couple of times by Bubba's 1st cousins bestfriends uncle.
And as far as clutches go, a good set of stock Borg Warners work just fine. I don't care what kind of clutches are used, if it's not built right, thier not going to live anyway.
Jake, I know which case saver you are talking about, the one that has the plate that bolts to the top of a regular center support with the little allen head screws. How about the other one, that required you to cut part of the original support lugs, and you have 4 little lugs that you push down in place of the portion of lugs that you cut off, then the center support snap ring holds them in place? It worked, but was a pain to use. I also have run into the one piece causing too much noise, which sounded like a bad U-joint when shifting between reverse & drive.
I don't really make my living building performance transmissions, I am in the retail transmission repair, and mainly build late model "virgin" units. I build a few performance tranny's for local guys, but not all out racing transmissions. But I prefer working on electronic transmissions.

Can someone proivide a list of transmission components that 1)Should be changed in a rebuild and 2)only changed if old part(s) is worn out. Sounds like trans "rebuild" means different things to different builders.

Each transmission differs and the application differs.

A stock rebuild TH350 would need (done right):
All new friction plates, band, seals, gaskets, thrust washers, bushings, hardened outer sprag race, modulator, filter, and IMO new steels and intermediate roller clutch.

However if it is for performance use at all, you must also include a valve body kit, valve body, or an advanced builders time to make mods to the stock valve body/trans.

Then there are all the worn out hard parts that you will see in a TH350. The case being a big one. Case, planetaries, pressure plates, pumps (also commonly beyoond use), etc.

To rebuild one right is a full day job for a builder with the proper tools. Clean and inspect parts, prep the case, change all the bushings, machine parts for performance use, clean and inspect replacement parts for those that didn't pass the first time, modify valve body, install new lip seals in the drums, assemble geartrain, check endplay and diasassemble to adjust, re-reassemble...

A Th350 is a pretty simple trans to assemble but it is one of the more troublesome due to worn out parts these days.

I've been doing them WAY too cheap at $650 with a customer supplied core for a mild build.

would the process be the same for a th400?