After blowing up my g80 which took out my driveshaft and pinion yoke I put it back together and my trans isn't working now. Anyone care to walk me through some diagnosis. Here's where I am at...

friday, gov loc dislodged the pin blew out the spiders and half of the carrier locking up the ring and pinion but the wheels spun free since the spiders blew out. This was leaving from a stop sign and wasn't a violent launch, just daily driving. Driveshaft broke rear u-joint and half the yoke, flopped around a bit and then slid out onto the road. Friend came with a strap and towed me 5 miles away, engine running for steering and brakes even though the d-shaft wasn't in. Lost some trans fluid but not what i would call alot, trans was in park idling.

monday, got a new shaft only to find the rear end was destroyed.

tuesday towed it home with a rope, this time 15 miles, engine idling, in park, no shaft lost some more fluid but again nothing earth shattering, I wasn't worried.

got my axle back yesterday, installed today and now all ready to go went to top off trans and it will not go forward, reverse only. I added 3 quarts showing on the dipstick, still no forward, doesn't even affect idle rpm.

Dropped pan, not a shaving or piece of anything metallic to be found, fluid looks and smells good. Reverse is as firm as ever, forward gears are nowhere to be found. I have an abs light, I will try to figure out what that is as it may be a clue.

 

hum.. thats strange.. since reverse works and first doesnt.... they use the same clutch pack. (i think)

 

Reverse uses direct clutches, 1st uses forwards. Does it have 1st if you pull the lever all the way down into manual low? If not it sounds like you sheared the teeth off the clutches in the forward drum... Or something else catastrophic to the forward drum. No abnormal noise?

 

No weird noises whatsoever, no forward movement in any lever position, no glitter in the oil (that I can see). One person I talked to mentioned the low roller clutch could have gotten trashed. Sounds like either way this thing has to come out and get looked at...any other diagnosis suggestions while it is in the vehicle?

The good thing is that my $900 converter is not full of glitter from my $800 tranny (yet)!

 

lo roller is probably gone. try to unplug the trans connector. should default to 3rd and it may move then. still needs a rebuild regardless

 

Should default to 2nd, no?

 

Yeah low roller clutch. Common on TH400s and 4L80Es. Same reason you don't start your burnout in 1st gear also. Basically the low roller freewheels too fast, coming apart (it's spring loaded).

 

Will your truck move if the shifter is in manual low?

 

nope... no forward in any position.
So this points to low roller clutch, is it hard to get at, or catastrophic? any kind of a rough idea how much has to come apart to change it or should the whole thing be flushed out when it comes apart? Any other parts or surfaces affected?

Trying to decide if I should tackle this myself or just pay it done by the guy who rebuilt it 8 weeks ago. Was perfect until my axle blew!

 

It's gotta come most of the way apart. Also when its apart, get rid of the HD-2 separator plate and dual feed it (with drilled out shift feed holes).