2500 4x4 Tranny Problem

Hi!

My chevy 2500 4x4 with a 350 engine and a th700r4 has started to act strange, i´ve lost the 2nd gear and O.D.... I´ve changed the oil, and the T.V cable plus i´ve adjusted it so its stretched at full throttle.

Any ideas of what the problem could be? Any chance to fix it without changing tranny?

/Sam

Did you lose reverse as well? If so, sunshell broke and a rebuild/replace is necessary.

//2000CAYukon

Nope, reverse gear still works fine.
Lost 2nd and O.D after i´ve been driving for 20-30 miles.

Well if reverse still works and you lost 2nd and 4th, the problem has to be with the 2-4 Band or the Servo.

You can pull the servo out to look at the seals but if the 2-4 is bad, you are looking at an overhaul/replacement.

//2000CAYukon

Okey, well how do i go about pulling out the servo? And how do i check/know if the 2-4 band is bad?

Sorry for the late response. The servo cover is held in place on the passenger side of the tranny with a large snap ring. There is a special tool that holds the cover in place while removing/installing the servo cover. It can be done without the tool; however, it can be difficult without the tool.

Since you lost both 2nd and 4th, the 2-4 Band is either not being applied (servo issue) or the Band is worn out. For it to be a servo issue both the 2nd apply piston seal and the 4th apply piston seal would have to be bad. Most likely the 2-4 Band is your issue.

Did you notice any slipping in 2nd or 4th before it went out completely?

//2000CAYukon

No problem, i´m just glad for the response. :)

Okey, so checking the servo could just as well be useless, how likely is it that both 2nd and 4th seal goes bad at the same time...so just as you say, probably the band has gone bad and a rebuild is the only option.

Before the went out completely there was some slipping, well driving up a hill in 3rd or 4th gear and it had trouble putting in 2nd gear....then all of the sudden they wore both gone, think 4th gear went out first....

If i decide to take of the servo cover, is it hard to check the piston seals? Are the pistons open for a good check when the cover is gone?

I doubt that both seals would go out at the same time. They use a cut seal but you can still check them for tears.

Here is a link on install a corvette servo on a truck so you can see where the servo is an the pistons.

http://www.gmfullsize.com/forum/showthread.php?t=98029

//2000CAYukon

One last question. Did you drop the pan and see if there is obvious signs (i.e. parts) in the pan?

//2000CAYukon

Yeah i dropped the pan last weekend, there where no parts in the pan/oil, just dark bad oil... should there be parts there if 2nd band has gone bad?

If you are using gasket sealer or silicone on pan.
A word of caution.
Do not use gasket sealer of any kind on pan gasket or pan.
There is a drain back hole under 2-4 servo.
If it gets plugged with sealer it will fry the band.

If you are using gasket sealer or silicone on pan.
A word of caution.
Do not use gasket sealer of any kind on pan gasket or pan.
There is a drain back hole under 2-4 servo.
If it gets plugged with sealer it will fry the band.

I have seen this damage done by silicone/sealants on pan gasket..If used the transmission/torque converter will be contaminated and fail...

When i pulled down the pan last weekend the previous owner had used some kind of sealer or silicone on the pan and gasket, i removed all the silicone or sealer and just used a gasket. But if the silicone has plugged any holes in the servo, could i still be able to save it if i remove and clean the servo? Or could the band be fried, so the only thing to do is rebuild?

When i pulled down the pan last weekend the previous owner had used some kind of sealer or silicone on the pan and gasket, i removed all the silicone or sealer and just used a gasket. But if the silicone has plugged any holes in the servo, could i still be able to save it if i remove and clean the servo? Or could the band be fried, so the only thing to do is rebuild?

If the drain hole was stopped up and fried the band very bad it is a dead duck.
Only hope is.
You might check on a longer servo apply pin.
They come in 3-4 different lengths.
Might add some more miles to it.
Good Luck