Mojave_Moze

My 87 4runner has been doing this for a while now, though I haven't had it out wheelin much lately, but everytime I put it in 4low, and first or second gear going uphill and sometimes on just rock obstacles, I hear a pretty horrid groaning/grinding from somewhere in the drivetrain

I'm pretty sure its not the motor, as everytime I hear this awful noise, I can feel it in the floorboards, but not the pedals so much. It sounds like its coming from the front end, like maybe in the case or transmission. The odd thing is, the truck might feel slightly rough when its making this noise, but it still pulls up the hill or over the obstacle just fine.

This is a bone stock rig as far as drivetrain goes. The clutch has been replaced a few times, and the output shaft from the case to the rear diff has been tightened once cause it was loose. Not sure if that could be a factor but thought I'd mention it.

the motor has always ran pretty good, and the truck never makes the noise unless its crawling in 1st or 2nd gear in low 4 range.

Could this just be as simple as gear oil level? or Could something be seriously wrong? Like I said, the truck feels a little rough while its making the noise, but never hesitates or slips or jerks at all. Also, pretty sure its nothing rubbing either, as I've trimmed and cut so much, that there really is nothing for tires or axles to rub on...

Any help or ideas??

ALLDATAdiy INFO

U Joints? Air in the cooling system?

Need to be more specific on where the sound is coming from.

Sensei

If the noise is only present in 4 low, as stated, then the noise is in your transfer case. Have you checked your fluid level in the transfer case ? Sounds like something is amiss in there.

Junkers88

Yeah at least check the fluid in the t-case. Might consider draining it and refilling with some new lube. Had a similar issue in an old scout and when I drained the juice it came out looking like strawberry jam *ick*, refilled it and never had an issue afterwards.

Mojave_Moze

Hm, now that I think about it...not sure I've ever checked the gear oil in the case...whoops. How bad of an idea would it be to run Synthetic gear oil? I've had good results with that Royal Purple stuff in my chevy. I know I have to run pretty thick stuff though, since its an '87. We've had the Tranny/case out many times over the years to replace clutches and it never occurred to me to check the fluid >.< I'll do that tonight and get back to everyone. Thanks for the help!

Junkers88

I run Royal Purple in the tranny and tcase of my 89 4runner, good stuff.

Mr.Utah

just finished with a similar issue, lube up your front and rear drive shaft SLIP YOKES and see if that makes any difference. It's almost a magical cure. Let us know more?

Mojave_Moze

I'll check the front Diff, but I KNOW the rear diff leaks, and its not the 3rd member housing gasket, its the ring seal, which is beyond my skills, unless its totally cool to air-impact the crush nut off the input yoke? O.o (input shaft? ...the thingy that attaches the driveshaft to the 3rd member >.< forgive my lack of correct terminology...) If it wasn't for the crush nut I'd have replaced the ring seal a long time ago, but didn't know how to deal with the crush nut.

The noise is more likely coming from the case than the rear diff, at least it SOUNDS like its coming from something under the truck rather than towards the rear, but I'll check both fluid levels and top em off and see if the noise goes away. I'll post some pics in a lil bit for reference. Thansk again for the help guys!

Mr.Utah

dont forget the slip yokes!

Mojave_Moze

Alright, I drained the fluid...and got about a handful of really grainy gear oil...and this:

the gear oil that came out....


It was kind of hard finding the drain and fill plugs...


Heres the front and rear diffs, dirty, but the front doesn't leak at all, the rear I had to add fluid to
Front:


Rear:


and what I'll be running in the case and diffs from now on:


Swapped the fluid and initial tests by running around in the yard in 1st and 2nd gear low-4, the noise seems to have gone away completely. Ill take it out this weekend and do some hill climbs to fully ensure the noise was in fact caused by low (and grainy) fluid.
Thanks for the suggestions!

dropzone

iTrader: (6)

if you found a wood or sheet metal screw inside your TC make sure the rubber boot (both of them) around your TC selector lever is intact...might help keep crap like that from falling in there again...

Mojave_Moze

The boots are good, I think that screw fell in when I had the sticks out when we dropped the case and tranny to replace the clutch once...was kind of wondering why I was missing an center console screw....lol

Mr.Utah

well, you found the screw!

Mojave_Moze

Thank god for magnetic drain plugs!