ToyoKev86

My dad and I just finished doing a front diff swap on my truck yesterday. It's a factory 4.88 IFS diff with a Spartan locker that I'd bought from a fellow member here. It also had some ADD parts; the actuator housing, clutch sleeve (I think that's what it's called), needle bearings, and driver's side stub shaft. We removed those ADD parts (except for the needle bearings) and reassembled the diff with my non-ADD axle tube and shafts. The stub shaft was replaced with a new oil seal that came with the diff, which we carefully tapped into the housing using the ADD clutch sleeve and a rubber mallet. After putting the diff back in the truck and letting the RTV set for about four hours, we filled it with Lucas non-synthetic 85W-140 gear oil.

This morning before heading off to work, I decided to test the front diff and locker by driving back and forth a short distance on my street in 4WD. I locked the front hubs and slowly drove forward in 2WD to get the oil to flow through the gears first, but that's when I noticed a small issue. The front of my truck was making a sort of groaning sound as it moved forward. To try to describe the noise, it sounded similar to the noise you'd hear in a car when you slowly creep into motion with the brakes partially applied. Anyway, after driving several feet, I shifted into reverse to go back to my starting point, and strangely I didn't get that groaning sound. I then shifted into 4-High and went forward again; the groaning sound returned. Reversed again and the sound stopped. The same things happened in 4-Low. Once I unlocked the hubs and shifted back into 2WD, the sound stopped completely and I drove off without any issues.

I can't say if the groaning sound is present at any speed because I only drove at 10-15 mph when testing the 4WD. The sound made me refrain from going any faster than that just in case I'd end up breaking something. The duration of the sound wasn't constant either; it'd come and go at random intervals, stopping for no more than a few seconds before returning.

I should note that my dad and I didn't mess with the gears at all when we were removing the ADD parts and swapping my non-ADD parts onto it. We also cleaned the surfaces of the mounting flanges for the diff cover and axle tube with brake cleaner, and some of the brake cleaner did get on the gears. I don't think we damaged the driver's side needle bearing when tapping the oil seal in because we didn't hit it hard, and we tapped it in just enough to where the top of the metal part was flush with the housing. When we filled the diff with oil, we filled it until the oil spilled out of the fill hole, so it's definitely full. There were also no leaks after letting it sit overnight, so I'm pretty sure there isn't an oil level issue.

The diff's previous owner informed me that he pressed in the needle bearings and installed the Spartan locker himself. He also told me it has .006" of backlash and a good bearing preload, so I kinda want to doubt that the groaning sound is caused by a backlash or needle bearing issue. He also assured me that the diff was not damaged when he removed it, has only about 100 4WD/off-road miles on it while in his ownership, and worked well the last time he used it. He's also a well-established member here, so I'm confident he was being honest with me.

To recap, I can only hear the groaning sound when going forward with the hubs locked, in 2WD and 4WD, and I don't hear it at all when going in reverse or with the hubs unlocked in 2WD. I'm pretty sure it isn't the brakes since it only happens when the hubs are locked. What may be going on? Could the brake cleaner getting on the gears be causing this? Maybe the gears weren't lubricated sufficiently because the oil was still cold and thick (I certainly didn't run in 4WD long enough for the front diff oil to warm up)? Any feedback is appreciated.

Thanks!

Edit:

I just ran my truck back and forth in 4WD once again but this time with the hubs unlocked. There was no groaning sound at all, so now I know for sure it only happens when the hubs are locked.

akwheeler

try one hub at a time, might help narrow it down to one side.

wyoming9

iTrader: (1)

Your sure you have 4.88 gears in the rear??

Same size tires front and rear??

Dry pavement sounds like torque bind

ToyoKev86

Yes, my rear gears are 4.88; the ring gear even has "488" stamped on it. It was a freshly rebuilt 3rd from East Coast Gear Supply with a little less than 120 more miles to go until the gears are broken in. I would think my truck would just stall if the front and rear gear ratios didn't match.

All four tires are the same size and are still pretty new so they haven't worn very much.

I tried to drive back and forth in 4WD in a straight line without steering too much (I steered only a tiny bit) to keep my auto lockers from binding up the drivetrain, but I guess torque bind could be a possibility.

muddpigg

iTrader: (1)

https://www.yotatech.com/forums/f116...ctures-100327/

ToyoKev86

Update:

I've got the problem solved. I didn't need to add grease to the spindle bushings at all. It was cold on the morning I first tested the 4WD with the hubs locked, so I think the low temperatures prevented the grease from properly lubricating the bushings. I tested the locking hubs again today after a long drive, and there was no groaning sound at all since the grease had warmed up. I'll also note that the locking hub knobs were pretty hard to turn on that cold morning, but today they were really easy to turn after the warm-up.