Buckdaddy

A bit of history…I rebuilt this transmission (due to 3/4 clutch) and it performed great for 4 months. I used a stock Transtec kit, only mods were beast sun shell, corvette servo, Transgo separator plate, boost valve, extended TCC valve spring controlling on/off lock-up.

I was driving to work one morning and started to go at the green light and as soon as I hit the gas things broke really bad underneath. When I got it home (1999 Z71) I found the rear differential destroyed. I replaced the rear axle and thought I was all fixed up but noticed a “warped” feel as I inched the truck forward. I pulled the transfer case and noticed I couldn’t turn the transmission output shaft while it was in neutral so I pulled the transmission and found the mess you see in the picture. The inner race and sprag or low roller clutch in the center support is totally destroyed
!
My question is this; what came first the chicken or the egg?

In other words…Did my tranny take out the rear end or the rear end take out my transmission? I’m guessing that when I hit the accelerator the back right wheel spun on the semi-wet road then the locker kicked in and that’s when the rear axle failed, the center of the carriage was broken not the ring or pinion…so my theory is the sudden rear axle crash took out my transmission…or am I wrong? Could it have been the transmission first?
I can’t afford this to happen again!

Thanks for your suggestions!

FirstYrLS1Z

iTrader: (4)

My guess,the rear end caused the tranny.
Seen many posts about tranny(both M6 and A4) destruction that had no effect on rear.
If the rear locks(breaks) and the engine is still applying power,something between the two has to go to relieve the pressure.
Many threads about sprags going.

AnotherWs6

iTrader: (17)

You already know basically what happened! You're right - the locker kicked in...... and then exploded. They are notorious for this. The factory units are prone to random failure, and it's usually pretty catastrophic for the rear. I think you hit the unlucky lottery twice - Once when the factory locker blew and then immediately after when it locked the rear. That's what I'm going with.

Please tell me that you didn't put a replacement factory locking carrier back in. When mine went - just pulling away from a stop light, giving a light jab of the throttle - it sounded like a gun going off under my truck. Took it apart and there was deep mauling all over the housing itself even. Those things are dangerous.

Game ova

Any time you lose ANYTHING behind the output shaft.... the transmission is done. Always good to pull it and go through it.

Buckdaddy

Thanks! I was looking for somebody to back up my theory of what happened, I was hoping it wasn't anything I did on my first rebuild. And yep, unfortunately I was running short on cash so I put in a used axle from the salvage yard. I hope it last until I can get a good locker in it.

It seems I keep getting snake bit, got me on both ends this time!

Buckdaddy

Just curious. Is it possible that any mods that create faster harder shifts could have contributed to failure of these factory GM lockers? I know we all put shift kits in our hot rods as kids and never had much problems but it seems to me that a quick shift on something like a Corvette or any little hot rod would most likely, because of the weight of the car (or lack of) it'd bark the tires or propel the vehicle forward if the tires caught traction (the old neck snapper!) BUT, considering a full size Z71 crew cab, with the extra weight there's too much traction to bark the tires and it's too heavy to be easily snapped forward by the propulsion of gear change, therefore, the drive line must take a real beating!

That's just a thought I'm putting out there I'd like your input on. I have read more that one thread mentioning rear axle/differential failure after transmission upgrades. Where do you cross the line at too much transmission for the drive train? You can definitely have too much motor for a drive train, right? It's like building a house on sand.

Basically all that for this...is high line pressure, corvette servo, etc. causing too much torque too quickly for the sloppy stock drive components in these heavy *** trucks?

performabuilt

iTrader: (25)

Usually when someone takes the rear end out this is what we get back also pretty common to happen when the rear locks down and breaks , Yes trans upgrades shift wise can hasten an already pending failure but not cause it.

Need4Camaro

iTrader: (1)

I feel like a dunce but I never near a rear axle failure automatically takes the transmission with it. Is this the case every time?

Game ova

Lost a rear end your, along with the driveshaft yoke. When I pulled the transmission apart to rebuild it.... This is how the roller clutch looked. And I would bet that yours now looks the same.

Buckdaddy

I really appreciate the opinion of you guys who are much more experienced than I am! I've been doing mechanic work for 35 years but only out of necessity most of the time and the automatic transmission was one of the few things I stayed away from until now... (financial necessity!)

I am using a center support assembly and rear planet from a 2003 4L60E that I have, isn't those the same as my '99? Also using input drum from the '03 because it doesn't leak. The '99 transmission seems identical to the '03 except for sunshell and reaction shaft. The reason I'm asking is because the forward clutch pack is very tight, could this be because I'm reinstalling saturated used frictions not new ones? Also, very little end play at output shaft with pump installed, both transmissions had same selective washer. I can push the shaft in a few thousandths, probably .008" or so, then it springs back out. The shaft turns pretty easily clockwise and you can hear the sprags but it takes more effort to turn counter-clockwise...Is this good to go or no?

Thanks for any help!

Game ova

Forward clutch clearance isn't near as important as the other shifting clutches, as it's always applied with the exception being reverse. And as for it being hard to turn backwards.... that's normal. Not as for your end play issue, im not sure what's causing that.... nor do I even know the recommended spec is for that on that transmission.

mrvedit

The output shaft is much harder to turn one way than the other. (In one direction the rear sprag freewheels; in the other direction the sprag locks and all the internals turn.)

Sure you can use most parts from the '03 in your '99.
The forward clutch should have about .030 clearance, not sure when less becomes a problem. How much do you have?

The input shaft end play should be .015 to .035. Obviously we want to aim for the smaller number. I've gone as little as .012 with brand new bearings and parts, figuring the final seating will be me a few thousands. But .008 sounds risky because it will tighten as the trans get up to operating temperature. You remembered the gasket between the case and pump?

Buckdaddy

I have about .015" on the forward clutch, I'm guessing it is a little more on the tight side because I am reusing saturated frictions...at least I hope that's why.
Yes, I did install the pump gasket. The first time I built this transmission it had a really tight input shaft end play it just seems a little tighter now.

AnotherWs6

iTrader: (17)

You don't AUTOMATICALLY lose the transmission if you lose the rear. Depends on what happens to the rear.

And sure, just like too much power you can have "too much transmission". But that's not likely what did you in. These lockers are grenades and it's just luck of the draw. Plenty of people have had them blow on stock, low mileage trucks. If you go onto some chevy/gmc truck boards you can easily see how prevalent it is.

It's kinda like the 7.5 ten bolt debate that's been raging for years. Some guys run 600rwhp through them without issue while some guys have them explode on the street with stock power.

Bottom line is - that locker is a time bomb and it;s not a matter of if, it's always a matter of when.

Ls1Ryan2002

Maybe it's a sign to ditch the ole 60e anyway lol, but on another note this was interesting to read about as I've only heard of this happening but never got to see the carnage in a picture. Sucks it took 2 birds with one stone, hope you get everything back to driving conditions.

Buckdaddy

Well, I thought it would be fitting to show the other end of the carnage. It sucks to have both ends go out but after all the comments it hurts a little less to know that the transmission I rebuilt is not likely the cause.

Now I shall comb the threads and posts to see what's the best locker to replace this junk with.

Thanks again guys!

Game ova

Just out of curiosity, what has been your experience when you had a sudden driveline failure? When you went to rebuild it, what did your roller clutch look like? Were the springs all intact, and not flat?

AnotherWs6

iTrader: (17)

Mine didn't take out the transmission. Carnage inside the rear end but that's it. For lack of a better term it fused one axle to the carrier while the other axle was just basically along for the ride. It made a God awful sound when doing so but I could actually drive the truck under it's own power. It had to be pulled onto a flat bed but it drove into my shop by itself.

I'm just commenting on the the G80 Gov-Loc (often called Gov-Bomb) unit's tendency to randomly and literally explode. As far as the trans goes, it lasted another year or so before suddenly quitting while driving 65mph on flat ground on the way home frm work one day. Ordered a new built one and put that in. No idea what it looked like inside, it's still sitting sealed up behind my house. For me, when a tranny goes you go out and buy a new one.