I have a 1997 Discovery 1 Manual Transmission. 4.0


Recently, while take a trip with light offroading, I heard a clunk, RPMa surged as if I had switched gears, and I lost all drive and coasted to a stop. When I tried to accelerate again with CDL off, there was a horrible grinding sound, as if the transfer case couldn't get into gear. I later thought that this was a differential failure and it was coming front the front differential flange, but I when I switched to CDL, grinding stopped and I was able to move it 1/4 mile to a place where I could work on it.


It already has a decent chunk when turning before this happened, so I started by replacing both CV joints, drive flanges, and checking the front half shafts and wheel bearings, which were in good condition. Once I got it all back together, I still had the same grinding sound with CDL disengaged, but I could still drive with CDL engaged. So I started to feel like maybe my front diff grenade.

​​

So I dropped the front driveshaft to isolate the issue and then had no drive at all, but no grinding. Next, I dropped the rear prop shaft and found that, with the front driveshaft on and the rear removed, I had drive with CDL again, so I figured it was a rear axle that had snapped and was feeling good that it wasn't the front differential.


While testing this, I was on a slow drive (about 30 mph) without the rear prop shaft, and I started to hear a metal rubbing sound coming from under the stick, as if a gear or maybe maybe clutch wheel were rubbing against the stick shift and forcing it out of gear. This happened for a few seconds as I was slowing down to pull off the road, then suddenly, RPMs spiked and were erratic, the clutch petal dropped almost all the way to the floor, there was some jerking, and I lost all drive again.


I was able to push it to safety, but while stationary there is now a low rumbling sound when CDL is engaged, the clutch seems to be gone, and it doesn't even die when in gear.


What am I looking at here? Did the clutch go? Did the transfer case burn out? Did my transmission blow? Do I have a torque converter issue? It seemed like it was a driveline issue, but now it feels like catastrophic failure of the worse sorts.


I did recently replace my slave cylinder but not master. Could all of these things have gone out at once? It was running fine before all of this, had new fluid in the transfer case and transmission.


Help! I'm at my limit of knowing what to look for or how to diagnose this when it seems like multiple systems are failing.

 

UPDATE:

I removed the rear diff and axles this weekend, and there doesn't seem to be any issue that would be causing my lack of drive when the center diff is unlocked. The prop shaft is intact and well-maintained, and I replaced the U-joints 6 months ago. I ordered a new clutch, slave, and master cylinder and plan to replace it, but before the clutch failed when I was driving it in front-wheel drive, it wouldn't have caused my driveline issue, right? There must be something wrong with the center diff.

I know no one has responded yet, but I just wanted to update you all in case anyone has any ideas for me. I guess I'll keep taking things apart.

 

I wish I knew more about your issue, but your troubleshooting sequence seems to be right. I’m sure you can’t harm anything by locking the Center Diff and driving with one Drive Shaft removed. This is a common troubleshooting procedure.

 

My understanding of how the trasnfer case works is that it won't if you have one of the propellor shafts off, the vehicle does not move. So, the fact that you took the front prop shaft off and got nowhere could be that - maybe someone more difinitive can chime in on this.

For me, I would work frontwords on this. Sounds like the transmission is functioning. Next is the t-case.

The grinding could be your high/low gear ring inside your transfer case that is making it so that you are not engaged. There is a large metal ring that shifts the transfer case from high to low. There is an in-between area that if the ring is not properly on the one side or the other, it's effectively in neutral. A quick check is to raise a tire off the ground and see if it is locked or will spin. If the tire does not spin, your transfer case is engaged - that would eliminate that as a possibility. But, the fact you are saying grinding makes me wonder if that ring is not quite where it should be.

I would assume a basic inspection of the outside of the differentials should tell you if they were damaged. But, if the t-case is functioning, but there is something internally going on with the differentials, front or back, then that may be what is happening with the lack of drive and goes back to what i mentioned earlier that I have always worked on the assumption if you take a prop shaft off, the vehicle does not move. I have a transfer case in the back yard that is open and I often play around with it and not certain where I read/heard that if a prop shaft is taken off the vehicle cannot move. I can spin the input on the transfer case and it will push output to at least one of the drive shafts at one time. I am pretty sure I have read that here about taking one prop shaft off, I could be wrong. If it is true, and one of the differentials has been damaged and is not functioning, that could be where to look.

 

You’re right about how an AWD transfer case works, except if you lock it (CDL). Then it works like a 4WD transfer case which is direct drive to both the front and rear.

 

This may, then, answer this question as to what is going on. If he is not locked in, then something is amiss with a differential if the vehicle does not move. If that is true, the differentials are not slipping.

 

UPDATE:

Thanks for the replies! I spent all day yesterday taking apart the rear axle and changing out the slave/master cylinder. It was pretty clear that my master had failed since it appeared to be leaking, and the oil was black. Unfortunately, I was sent the wrong master cylinder, so I couldn't put it back together to see if it fixed my clutch issue, but I feel pretty confident there. As far as the driveline issue goes, since I have now checked both front and back diffs/axles and both prop shafts, my next thinking was that it might be that the rear output flange on the transfer case has been stripped. I've been needing to check my handbrake anyways, since it really doesn't work, so I jacked up both rear wheels and had the CDL off and handbrake off. To my surprise, the drum would not move and seemed locked, even though the handbrake was not engaged. I had to drastically loosen it to get the drum to give up its bite, but I have now gotten it to where it needs to be.

I don't know if this will fix my problem until my new master cylinder arrives, but I just wanted to keep this thread updated in case someone else has the same problem one day. Could I have hit the handbrake drum on something while off-roading, causing me to lose loss of drive suddenly? I hope this was the issue and the transmission brake got engaged somehow, leading to the loss of drive and grinding sound I heard with CDL off. It could also explain why I had no grinding when the rear prop shaft was removed because the locked transmission break would only affect the rear axle.

 

A few years back, my son dropped the front driveshaft ( the u-joint bolts fell out somehow at a stop light) found all but 1... and it wouldn't drive anywhere, and wouldn't stay in place in park. I was a long ways away so he rolled it into a parking lot, blocked the wheels and we fixed it the next day. 2 weeks later, it started making a bunch of noise, he had run it out of oil and grenaded the motor. That was the end of that one. Ended up with another D1, 1999 and he doesn't get to drive this one....