Corvette Servo DISASTER

[JPVortex]

hello yall, so I went to put a corvette servo and a longer pin in my 4l60e in hopes of tightening the band clearance and getting 2nd gear back. I did the whole job and didnt get the snap ring back in all the way. I got about a mile down the road and the trans fluid was dumping out.

I limped it home in 1st and got it seated correctly. I forgot to top off the trans fluid(lost about 2 quarts) and went for a test drive.

No cracks in the housing from what I saw and the cap didnt come off all the way.

Was a couple miles down the road when I smelled a burning smell, followed by loosing every gear. I pulled over shut the truck off and my brother brought me trans fluid when I realized where I messed up.

i was able to get the truck home and it actually does have 2nd gear but now 3rd and 4th gear are totally gone, just free revs.

So I went to double check my work and pulled the servo back out. I noticed right away the 4th gear piston seal totally ripped up and definitely was not sealing right, so I have a new seal on the way.

My question is do you guys think this seal is what is causing me to loose 3rd and 4th or do yall think running low on trans fluid burned up the clutch pack?

 

[Erik the Awful]

If you're low on fluid the transmission typically won't want to shift into drive or reverse without revving it up. If it went into gear fine, then it's not likely low fluid caused it to lose 3-4. Without looking at an apply chart, I'd suspect the seal.

 

[tayto]

try the seal but don't be surprised if 3/4 burnt up. running auto transmission low on fluid is very bad

 

[Hipster]

No second gear, and thought a vette servo would get it back? Me thinks you finished killing a trans that was already on it's way out.

 

[JPVortex]

No second gear, and thought a vette servo would get it back? Me thinks you finished killing a trans that was already on it's way out.

Vette servo with longer servo pin. And it actually does have 2nd now lol just no 3rd or OD

 

[Supercharged111]

No second gear, and thought a vette servo would get it back? Me thinks you finished killing a trans that was already on it's way out.

This. And a faulty install may have further hastened its demise.

 

[Hipster]

Vette servo with longer servo pin. And it actually does have 2nd now lol just no 3rd or OD

Just kinda think there's more going on here and that this fix might have been only temporary at best. Like the band is close to being toast and close to metal on metal, if not already, on it's corresponding part.

 

[Supercharged111]

Vette servo with longer servo pin. And it actually does have 2nd now lol just no 3rd or OD

So I used to run my 4L60 in speed density. I didn't realize on the black box this meant full line pressure. Needless to say, I cracked the case. It broke the servo retaining portion partially off of the trans and caused it to puke out a couple quarts of fluid. Truck only lost 4th IIRC but shifted weird. I only knew something was wrong when I shifted from 3rd to 4th with my trailer behind me and there was no 4th. Finished my day picking up a car and only ever drive the truck again to go the junkyard for a 4L80 builder and to the shop to do the rebuild/swap. That servo can do some real weird stuff when it isn't right, but losing gears is usually a one way street.

 

[Hipster]

So I used to run my 4L60 in speed density. I didn't realize on the black box this meant full line pressure. Needless to say, I cracked the case. It broke the servo retaining portion partially off of the trans and caused it to puke out a couple quarts of fluid. Truck only lost 4th IIRC but shifted weird. I only knew something was wrong when I shifted from 3rd to 4th with my trailer behind me and there was no 4th. Finished my day picking up a car and only ever drive the truck again to go the junkyard for a 4L80 builder and to the shop to do the rebuild/swap. That servo can do some real weird stuff when it isn't right, but losing gears is usually a one way street.

I've only built 2 700r4's, so not an expert by any means, but the longer servo pins available need to be measured, checked, verified, and trimmed accordingly to verify apply. You just don't throw the shyt together. Couldn't get it to seat because there was too much pin in there? MAYBE, OR MORE THAN LIKELY?

 

[tayto]

I've only built 2 700r4's, so not an expert by any means, but the longer servo pins available need to be measured, checked, verified, and trimmed accordingly to verify apply. You just don't throw the shyt together. Couldn't get it to seat because there was too much pin in there? MAYBE, OR MORE THAN LIKELY?

this seems to be a common mistake in the DIY transmission repair crowd. have read of lots of folks don't seat the snap ring, servo pops out and then lose all gears. usually the ones that keep driving are the ones that wreck stuff (no offense OP).for anyone reading, the worst thing you can do to automatic is run it low on fluid. this is why i calibrate my dipstick as even OEM stuff can be wrong and cause your new or used transmission to burn up. also, if you have a major leak or KNOW you're low on fluid don't "limp it home". pull over and figure out how to get fluid.

yes servo travel should be checked. doing something like installing a longer pin is a bandaid fix until the owner can save up for a rebuild or new vehicle. who knows if a fix like this would have worked for a few days or years....