Hub/diff/transfer case problem

took the nav out for a quick beach run yesterday , all was good untill coming off sand onto ramp. Drove onto ramp for around 10 meters , stopped took it out of 4wd, unlocked hubs and kept driving then felt the diff starting to bind up and shake through drive train then got a massive clunk and it seemed to release the diff bind, smooth sailing from then on. Is there a procedure for taking it from 4wd to 2wd ie unlock hubs first then shift to 2wd or other way round? Its an 88 D21 King Cab.

Should be able to shift in and out of 4WD with the hubs locked

Very strange behaviour. You only have to disengage one element (transfer case or either hub) for the whole system to release any windup.

You shouldn't have to reverse to unlock the hubs, besides, when you pulled the stick to 2H as I said any windup should have been relieved.

All I can suggest is try to get it to happen again, and once you've worked out how to replicate the results, follow a process of elimination to work out the cause.

Second what Dion Pinelli said.

Dave.

Hmmm, would it have anything to do with different sized tyres on front and rear?

How big a difference are we talking?

Still won't have anything to do with the strange behaviour when the stick is in 2H and the hubs are unlocked.

275/70 on front 275/75 rear 16 inch rims, thanks for the help lads

Ronnie said:

275/70 on front 275/75 rear 16 inch rims, thanks for the help lads

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that may seem like a fairly small difference but there is a difference of 8.33cm rolling diameter. that's signifficant! you will bind up with that sort of difference for sure, especially on tarmac where you have so much more grip.

i'd strongly recommend you get the same each end. i sometimes need to reverse back about a meter or so to disengage 4x4 with my D22.

it is a little strange that it happened after you unlocked the hubs though. free wheeling hubs shouldn't hold any pressure??!?!??! like Dion said, try and replicate the scenario and eliminate possible causes.

Well running different sized tyres wouldn't help.

Dave.

Yeah, the diff ratios are the same, confirmed by good mechanic. I'm getting suspension kit done in a week and the next day will be tyres and wheel alignment so I'm hoping this will sort out any gremlins. Will be posting up a thread in rides once this done and post detail ofcourse, will update after trip to beachport for camping and wheeling. Thanks again for ur wise words navara yodas.

I just noticed today that if you unlock the hubs, then apply power through the diff, they stay locked, until you go off drive and into coast. This is less marked than in vehicles with automatic hubs, but it's still there slightly.

Might help you out, but doesn't explain why pushing the lever into 2H didn't resolve the issue straight off the bat.

when u say from coast to drive you mean from neutral to in fwd gear?

Ronnie said:

when u say from coast to drive you mean from neutral to in fwd gear?

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When I say 'coast', I mean wheels-driving-engine.

'Drive' is engine-driving-wheels.

Ok got u, took it out for another run on gravel n grass this time. Was fine then same thing happened when driving back onto tarmac, this time though I tried puting it into reverse and then continued driving, felt the bind release instantly and no clunk! Sorted, thanks all.