VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc '91 4wd chev pickup drive train

Hi guys(gals), It's a 1991, 4 wheel drive, short bed, 5.0, manual 4 spd trans with overdrive. AND it gets 22,23,24 mpg. It has ratcheting noise if my toe touches the clutch even slightly when starting out. Most of the time I can avoid the noise. Once in awhile in the first 10 feet something seemed to bind up but a couple feet backwards and it would be ok. I drove it 5mi today and it really bound up fwd & back. If I put 4wd in neutral then back in gear it'll move a foot or so freely i think.

I hav a brand new Boston rebuilt 700R4 (with transfer case) (with new T-converter)I'd like to put in. Also have a good? spare 700r4 and another spare transfer case. I'd like to know more about differential and transfer case gear ratios. Also wondering about computer issues or if vacuum will operate the automatic. Other than that I guess I need to remove present flywheel. Any thoughts? Thanks, LtLarry larp@worldpath.net

I think that you will at least need an aftermarket controller for the lock-up on the torque converter. Check with Summit or on of the other aftermarket suppliers. They have them.

If I am reading correctly the problem occurrs in 4wd only. Are you using 4wd on hard surfaces? If so cornering or different rolling diameter wheels will cause the driveline to wind up and in severe instances will do major damage. 4wd is designed for use where wheels can slip and allow driveline to unwind.
If it does it again lift 1 front wheel off the ground allowing it to spin free before driving. On hard surfaces use 2wd only
Tony

I was a little unclear. Something is really binding -4L,4H, and 2. Won't move in a straight line more than a foot. It may be pushable if it's in neutral, I'm not sure yet.
It's as if there were 2 chains and one had jumped 3or4 teeth. or 2 clutches in the transfer and both are engaged-fully. another analagy would be frozen calipers, almost dead locked to disk. However it does move very freely 6".When this happened I had just driven 5or6 mi trouble free.

Check the brakes!and wheel bearings! But why not just pull the drive shafts and eliminate or cuss the driveline.

As Mack suggested remove the rear of rear and front of front driveshafts, with transfer in any position and main transmission in NEUTRAL turn the drive shaft, it should turn easily if it does the problem in differential or after.
If the park brake is at rear of transfer make sure it is free.
Not knowing the setup and your description not clear, is it automatic or manual (you mention clutch and t converter). If automatic the parking pawl in the main transmission may not be retracting properly.
Tony

Thanks, I had it brought home. It moved freely enough with small enough bind so I think I felt it at the right front caliper. After calming down a bit and browsing the manuals and looking at your input it occurred to me to do as you guys suggested.
-isolate problem to a wheel or wheels, a differential, a u-joint, transfer case, or manual tranny. It acted like it was in High and Low at the same time, or Fwd & Back, or electronic syncro was engaging both sides at once. So i guess I've got to logically track it down.

I thought someone might've had lots of experience on these locking up a few hundred times and say with me it was a shifting rod or speed indicator or clutch coil relay or the thermal thing. and I'd start there. But I'll begin at the starting point.
Thanks to all offering help, LtLarry

Larry,
My son has an 86 K/5 Blazer but he has an automatic in it (700 R4) (POS if you ask me) and the front axle U joints were the problem. They were dry and crusty causing everything to bind
John