i have a problem w/ the rear end on my 85 4runner. Ive got a detroit w 5.29's and there is too much play in the rear. It vibrates extremely loud when driving on highway. I bought the whole third slightly used and it did have a little play when i first installed it, mild vibration around 70mph and ran fine for a long time (at least 5,000 miles). Recently it has been getting worse, quickly. Now vibrating is a loud roar at round 45mph! reached under there and I could rotate the driveshaft back and forth a little over a 1/4 turn before it engaged rear axles. So i pulled the 3rd today to check it and it really didnt have any backlash, was same as day i installed it. Im not too familiar w setting up gears/diffs so i was wondering if anyone else has had this problem? Hope I dnt have to purchase a new locker. I tried to search older posts, if you know of one please point me in right direction. Any input is much appreciated, thanks.

 

Welcome to YT. Gear setup is the number one reason for failure.

http://www.gearinstalls.com/ will be a very helpful site. If you don't have the tools or experience might be a good idea to get some one to do a "health check" on it. ZUK used to do this and was worth the price of shipping. He found that a set up a local guy here did reused the old bearings. ZUK was taking a break from gears. Search for davesperformanceoffroad.com or perhaps Marlin Crawlin, or even Trailgear. Randy's ring and pinion may do it to.

 

I'll check some of those out. Thanks for the help

 

Well, it's pretty obvious to me. If the ring gear backlash appears to be fine, then it's gotta be either the side gear backlash or a problem with the splines on one or both of the axleshafts. Which means the locker is damaged internally or the axleshaft(s) need replaced. Whether it's worth the price to get a broken locker fixed or just buy a new one is the only relevant question. That I don't know. All I do know is those Detroits are about as spendy as they get. So we're hoping it's just the axleshaft(s), which are slightly cheaper.

And BTW, these things happen even with properly installed gears. Which isn't rocket science, as I've stated countless times. And can be done by anyone with the necessary tools(or a trained chimp for that matter). So don't go putting the blame where it doesn't belong. ABUSE is the leading cause of gear failure IMO, NOT installation error. To blame the installer every time something goes wrong is totally naive. That's PURE BS!

And this is definitely NOT a "gear failure" issue anyway. Like I said, it's the internal locker components(which are setup for you by the factory prior to gear installation) or axleshaft wear. IT HAPPENS!

But by all means, if you don't believe me, pay a "professional" to tell you the exact same thing.

Good luck!

 

Who installed the gears? check the pattern of the ring and pinion. its fairly easy to do. I recently put lockers in 4.88 factory diffs... it was slightly easier for me since the diffs were already assembled.

 

When you installed the third did you inspect the outer shaft bearings? Not a good thing in a semi-floater design if those fail. As for the bearings in the third no way I know to inspect those without disassembling the third. Will costless if you find the problem and repair it now than wait for something to fail. Do it yourself or pay some one else either way it needs to be done.

 

So i had a chance to inspect the splines on the axles and inside the diff and there was no signs of any excessive wear. So i can rule that out at the root of the problem. Also, i did the best inspection of the bearings and locker itself without tearing it apart (was pressed for time) and everything looked to be fine. Btw, there was NO metal shavings in the housing or the fluid that i drained. Talked to a friend and he said it might be as simple as my pinion nut being lose. Could it really be that simple?? Havent had chance to try this yet bc of work schedule. Anyway, ill give it a try and if it doesnt work ill have to take it to a shop or someone just plain smarter than me. Again i want to thank you guys for all your input, i really appreciate it.

 

ok so just an update, me and a friend took apart the rear 3rd (including completely disassembling the detriot) and still could not find any sign of wear or failure. So just decided to put it all back together and throw it under the truck. Still has bout 1/6 of a turn of play in it. Can tell its not the ring/pinion, its something w the detroit. Ddnt fix a thing. So i guess new plan is to purchase new locker and use it to replace the limited slip i have in the front 3rd, then swap that one to the rear and put the loose 3rd in the front axle. Should be fine up fron bc will only be used at low speeds. Anyone have an obection as to why that new plan wont work?