Automatic Transmissions

Dyno247365 · #1 07-16-2006, 10:40 PM

The car can drive fine and shift fine for several minutes and then everything slows down, the rpms, the shifts get harder and you've lost 3rd suddenly.

Say a tech diagnosed your car and told you that the valve body in your A/T is going. What IS the valve body and what parts need to be replaced. What gets replaced in an overhaul?

Dyno247365 · #2 07-18-2006, 12:18 AM

No tranny specialists huh?

Hi Tech · #3 07-18-2006, 05:36 PM

I'm not a specialist, but I have rebuilt plenty of transmissions, and I'll at least be courteous enough to take the time to try to answer your question, since no one else has.

As you remove the transmission oil pan, the main internal part that you see, is the valve body. It's simply the case that retains the valves, that control the fluid pressure for each gear shift.

The reason that it's called an overhaul, is that most everything that is a wearing component, will most likely be replaced, such as clutch discs, steel discs, o-rings, seals, etc., but not usually the hard parts, such as clutch drums/pistons, gear sets, shafts, etc., unless they are excessively worn or damaged, and need to be replaced.

It's possible that you could even rebuild the auto trans, yourself, providing that you have the tools that you'll need, and at least a reference manual to guide you through it.

If you're referring to your Camaro tranny, the tools will cost around twice what you can have the transmission rebuilt for, at your local shop. I know, because I bought all the tools, to not pay someone else to do what I'm capable of doing, myself!

Hope that gives you an idea, anyway.

UncleBob · #4 07-20-2006, 02:53 AM

if you have a TH350, then anything that is wrong with the tranny is mute. They are so cheap to get remans, its not even worth messing with them. $500 is the starting price.

Your question is a little too simplistic to answer directly. The valve body is a very complex assembly with many many components involved within that assembly. the mechanic very well could be correct that its a problem within that valve body, but what would be involved in fixing it is far from necessarily simple or obvious. YOu could of course get a valve body assembly and replace the entire works, but the cost vs getting a reman....with a warranty mind you....is questionable.

Hi Tech · #5 07-20-2006, 01:11 PM

Quote:

if you have a TH350, then anything that is wrong with the tranny is mute.

They are so cheap to get remans, its not even worth messing with them. $500 is the starting price.

So, since it's not worth messing with them, I should stop rebuilding TH350s for $150 each, and just buy them for $500 each, instead...

If you're going to take it apart, anyway, to replace only the valve body, as UncleBob suggests, it's only logical to rebuild the whole transmission, because it won't take that much more time to do, and you'll have a fresh, dependable transmission after that!

UncleBob · #6 07-20-2006, 01:15 PM

Quote:

Originally Posted by Hi Tech

So, since it's not worth messing with them, I should stop rebuilding TH350s for $150 each, and just buy them for $500 each, instead...

If you're going to take it apart, anyway, to replace only the valve body, as UncleBob suggests, it's only logical to rebuild the whole transmission, because it won't take that much more time to do, and you'll have a fresh, dependable transmission after that!

if you already have the tools and knowledge to rebuild your own trannies, then of course its more economical for you to rebuild your own tranny. That doesn't even need to be said, does it?

If I have a full machine shop and have been rebuilding engines for 10 years, then I'm not going to pay someone else to rebuild my engine now would I?

The person asking is the person I was directing my advice to. If he's not even sure what a valve body is and what it does, then I wouldn't recommend him attempting to rebuild it himself....not when the price difference is so reasonable.

Hi Tech · #7 07-20-2006, 01:56 PM

Quote:

Originally Posted by UncleBob

The person asking is the person I was directing my advice to. If he's not even sure what a valve body is and what it does, then I wouldn't recommend him attempting to rebuild it himself....not when the price difference is so reasonable.

How do you expect him to learn how to do it, if no one will take the time to teach him, or explain it to him, or if he never tries to do it, himself?

Been there, done that!

I'd encourage him to rebuild it, as a learning experience, at least to understand what the parts are, and why they need to be replaced.
At the least, he could stay at the transmission shop, and watch while they rebuild it, to see what's involved!

The Haynes manual for GM Automatic transmissions is easy to read, shows step by step disassembly, and reassembly, and explains procedures of how to remove parts, by using whichever tools are needed.
Most valuable $10 I've ever used, or referred to anyone who asks these same questions!

UncleBob · #8 07-20-2006, 05:45 PM

I'm not even sure he's interested in rebuilding it himself, but either way, I wouldn't recommend anyone jumping into this on their main ride with no experience or help from someone experienced in rebuilding trannies. Its one thing if you have a toy that isn't an important means of transportation, its another thing when you're relying on it.

I am all for people getting their hands dirty and learning....but I think there are better ways of going about it than this particular situation. Hell, TH350 cores are literally free. Go to your local tranny shop and ask for one nicely. Then play with that one. If you feel confident about the build, then slap it in there and see how well you did. Its not like it would cost you anything extra that way.

Hi Tech · #9 07-21-2006, 12:36 PM

UncleBob is right.

I withdraw my comments, based on conclusions without enough information about the questions asked.

Get the transmission rebuilt, for what it will cost, and just get it in the car, drive it again, and forget about it.

Good Luck, Quicksilver, whatever the outcome.

Dyno247365 · #10 07-23-2006, 08:34 PM

I bought a rebuilt tranny for 250 from a junk yard. It's a 700R4 and I'm pulling the old one off next week when I have more time. Here's the progress and the junk tranny:

Replacing transmissions is a lot easier than learning how to rebuild one.

UncleBob · #11 07-23-2006, 10:18 PM

that tranny don't "look" very "rebuilt"

700R4 is definitely a different deal. They are a lot more expensive. Me, I'd probably convert it to a TH350....The 700R4 can be a good tranny....but they are more fragile and more expensive. The OD is nice though.

Dyno247365 · #12 07-23-2006, 11:58 PM

For lack of a better word, the junk guy told me it was recently rebuilt and I saw the car it came out of before I bought it, good enough condition firebird. RIP

Yes, the OD is VERY nice.

MetalHeadZaid · #13 07-25-2006, 02:40 PM

not that im trying to influence you or sound like an ass, but why didnt you use this as your chance to convert your car to manual? i mean, i have seen your posts in the 240sx forum, and i was under the impression that you are perfromance oriented, (not that autos cant be fast) so wouldnt this have been a good opertunity?

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