70 series help

[97lux]

Hi I would really appreciate any advice/help with my 1987 bj74. Its a 13bt with an auto that once reaching 50kmh makes a whirring or whining noise and carries on to to 70kmh then disappears. It will also in low 2wd lock up both wheels while turning hard to the left or right at idle speed on sealed road or gravel but doesnt do this in high 2wd. Ive recently had front and rear wheels bearings replaced and all brakes reconditioned. Also all new oils in the rear diff (lsd) standard in the front diff, correct gl4 oil in the transfer and had the auto trans serviced. Ive spoken to different mechanics sum suggesting its the transfer box and sum saying its the rear diff. Please any help, thanks.

[muddy]

When you select low range - it should automatically engage 4WD. So the locking of the transfer case is normal. The noise may well be a universal joint due for replacement. Check for any play, and if they feel OK, get some grease into them.... Eliminate the simple and cheap possibilities before the big ticket items...

[mudlva]

Need more info.
You mention locking up both wheels in low TWO wd?
Im asmuning its the locked up rear wheels?
Does that mean you are in low box with hubs out?
If that is the case then its a busted front diff or cvs that is locking up the prop shafts and then locking the rear diff up as well.

If your hubs are engaged whilst driving in hi box 2wd then a rummbling will be made as front wheels are turning the diff and prop shaft and with no back pressure then back lash will generate noise and rummbling.

If hubs are out and box in 2wd get underneath and free turn the front prop by hand. If its bound up then again cv or diff busted.

If cv is busted then it may not be disengaging from hub fully and turning at the speeds mentioned

Just a side note make sure box move between 2wd and 4wd freely if not fully engaging one way or the other then possible trans box issues.
These boxes are generally pretty bullet proof with basic maintanance. Ive beaten my unit up for years and when i pulled in to fit low range gears it was still mint.

[97lux]

Thanks for your help muddy. Ive recently replaced a uj for a wof and greased the rest while I was under there and I agree with checking all possibilities before doing the big ticket items and thats where all the experience and knowledge of guys on here is priceless to help out us young guys with so much to learn. Cheers

[97lux]

Thanks mudluva. Sorry for the lack of details. Yes the front hubs were unlocked while It was in 2 high and low while listening to the rear wheels locking up. Its been used mainly used as a road truck and occasionally used 4wd while towing a trailer load of wood off a paddock nothing hard out and i was being gentle on the drive line. But could there have been a problem or mistake made to the free wheeling hubs when the front wheel bearings were replaced that could possibly cause the rear wheels to lock up in low box? Cheers.

[mudlva]

Humm ok.
Pull the fwhs off and she if probs cont.
Still intreged on the rear locking up tho.
Head back under the front the front with hubs removed.
Put trans box in 2wd turn prop shaft. Should be free
Engage 4wd hi. Front prop shouldnt turn. Engage drive and see if wheels still look up. If moving freely all good
Engage 4wd low. Repeat above. If moving freely all good.
Knowing that there is no resistance moving prop when not locked removes diff head issues.
If the wheels lock up with no hubs in confirms damage in t/box. With the problem initail in low box. Im now moving towards broken teeth or similar on low range sprokets