Drivetrain Failure

[d901560]

My Defender left me stranded X-mas Eve night. I was pulling away from a stop sign when I lost all forward momentum. When I tried to let out the clutch to start again, there was some clunking noise and vibration, like it was trying to engage but could not. After trying to start repeatedly, the noise went away when I let out the clutch and didn't seem to engage at all. I can push the truck with the transmission and transfer case in gear and I don't hear any unusual noises. I plan to take a closer look at things later today, but right now I suspect the clutch. The strange thing is that the clutch supposedly was replaced just prior to when I purchased the truck about two years and 12,000 miles ago. I have not noticed any slipping of the clutch or unusal noise from the throwout bearing. Any help would be appriciated. I doubt I'll try to replace the clutch myself in the driveway, but I would like figure out what is wrong and how much $$ I'll spend before I take it to the shop.

[evilfij]

Busted CV or busted diff either in an axle or the T-case. Try driving in diff lock.

[d901560]

I tried locking the diff and it still would not move. Even locked in low, it didn't make a difference.

[evilfij]

Busted diff in t-case will do that.

Drain and see if chunks fall out.

[TDI Guy]

also when you put it in gear and let out the clutch, look under it and see if a driveshaft is turning. If it is, the problem is in that axle. Then put it in diff lock and it moves that just confirms it.

[Roadsiderob]

I'd pop the pto cover and see if the transmission output splines are stripped...especially since your truck is a 1994. Usually if a clutch goes out it will feel different if it is that sudden. If the problem is in either axle or the center diff, the truck should move once the center diff lock is engaged (light on).

[evilfij]

Oh a 94 without the update . . . I am suprised it lasted this long.

Center diff will not function even with diff lock if it is completely blown.

[d901560]

Here's a little more info on the truck. It's a 94 with a R380 transmission. According to the truck's service history, the LT77 was replaced with R380 at about 30k miles. The truck has 121k miles now. I replaced the oil in the t-case last April and did notice a few very fine metal shavings on the plug, but it did not seem bad. The t-case is leaking from the rear output seal, but I keep it topped off so it never gets low. The drive shafts do not turn when I let out the clutch so I don't think anything is wrong with the axle diffs or CV joints. If I raise one tire and try to rotate it while the diff is locked, would this confirm the diff is bad if it tire rotates? I haven't had time to drain the oil and pull the PTO cover yet.

EDIT: I just just tried to rotate the raised tire while the diff is locked and it would not turn. It spun freely while unlocked with no unusual noises from the t-case.

[Roadsiderob]

Brian,
When you lock the center diff you mechanically couple the front output of the t-box to the center diff housing. The rear output is then driven through the gears inside the center diff. If neither driveshaft is turning with the center diff unlocked, then you can probably rule out a problem in the axles. Next, lock the center diff and jack up a rear wheel and leave everything in gear. You should not be able to turn the wheel if the center diff is intact. I would remove the PTO plate and input gear. This will allow you to inspect the splines. With the gear out you can check the integrity of the transmission. I have seen a couple of cases where the mainshafts have sheared off internally. Good luck and feel free to call me at the shop during business hours if you need any assistance
Rob

[pendy]

If you suspect the clutch. Can you push the vehicle when it is in gear? You can pull the transmission dust cover next in you suspect the clutch.

JP