w/o taking the xmission out

[croatankid]

I have a a4ld. It needs rebuilding but it's a daily driver. I can lay it up a few days but not long enough to do the whole thing. I want to do what ever I can w/o taking it out. I want to rebuild the valve body, replace the vacuum mod, and replace the servos and filter and install a drain plug. Is there anything else I should do while the pan is off?. .

 

[RonD]

Not much else you can do

The clutches and bands(brakes) wear out just like clutches and brakes do on manual trans and wheels, just not as fast since they are cooled, well cooler, lol.

Those are the parts that are changed with full rebuild, also main pump

All automatics run on pressure, ATF fluid pressure, the pressure comes from the main pump(front pump) and this pressure is then routed thru the Valve Body.
The Valve body controls where the pressure goes, to engage or disengage clutches, to engage or disengage brakes(bands)
Disengaging a clutch doesn't mean that part of the transmission will stop spinning, thats where the bands(brakes) come in after clutch is disengaged the band clamps on that part to hold it from spinning.

If pressure is low then you get slipping, if low enough then no GO at all
You need 125psi to go forward, 175 to Reverse
This is why reverse is often lost before forward

Pressure is often lost in Valve Body seals and gasket, so a good thing to rebuild to get the most miles from the clutches and bands, but they do eventually wear out.

 

[croatankid]

Thanks for all that good information. Yes, I want to do a complete rebuild. If I do the valve body and the xmission at the same time, and there's a problem, it will be harder to isolate the problem. So I will do one, the VB, and see if it works right, then when I have more time, I will do the whole thing.

 

[RonD]

Yes, good plan

 

[Shran]

I'm just curious - is something in the trans not working right? I mean... rebuilding the valve body, replacing servos, etc is really more than you need to do if the trans is working fine. If it's a high mileage deal and/or it has some issues then just do a full rebuild... when it goes, you're going to be removing or replacing all of that anyway.

If it's working fine just do a filter and fluid change and install your drain plug, don't fix it if it ain't broke.

 

[bobbywalter]

i cant believe that line of thought. the valve body is very susceptible to malfunction from worn torque converter and rotating part wear particles..every time you work on it your taking a chance of janking it up permanently.. vicious cycle.


if your time limited, swapping in a known working unit is the best use of limited time.

or scheduling a bench build date with a known local builder that handles these pieces of crap. they will have it wound out in half a day. so two day turn around on your back is easy to pull off.

 

[adsm08]

or scheduling a bench build date with a known local builder that handles these pieces of crap. they will have it wound out in half a day. so two day turn around on your back is easy to pull off.

Yeah. On a 2wd I could have the trans out and apart in about an hour.

Ask me how I know.

 

[croatankid]

Yes something is wrong with the tranny, I don't know how many miles are on it, it hardly engages in 3rd gear and it makes a rattling sound when I come to a stop. I want to do a complete rebuild but I'm timid about doing all at one time. If I do the VB first and test that, I'll limit the number of places I might screw up. So I want to do some and test it before moving on. It will also limit the time the truck is down at a time though over all it will down longer in the end.