4.88/4.77 review

[Andre75]

I finally got a chance to put some miles on my new, mismatched gear setup at Uwharrie last weekend. I've had the new rear axle installed for a few weeks, and the difference on the road is very noticeable. It's got a lot more get up, but the increase in mileage seems to be negligible. I like the Speedo being accurate, but it feels like I'm driving faster :D

For 4wd situations, I measured the effective tire radius as accurately as possible to compensate for the gear difference. A level and tape measure was the best I could do, but I came up with a tire pressure of 16psi in front, and 21 in the rear. I've also got newer tires on the rear, which helps me get the 0.35" difference in radius I calculated to equalize the ratio. I was running around in 4low (Teralow3:1) the whole weekend, and I never noticed any binding or pulling. We did notice after the last trail run, that the front diff was extremely hot :confused: The front diffs of the other Zu's with us were cold by comparison. I also noticed a whining sound on the way back from the trail in 2HI with the hubs unlocked. Both diffs had plenty of fluid.

We came to the conclusion that the gear difference, multiplied by the low range, caused more pressure, and therefore heat on the gears. The excessive heat would seem to account for the increased noise.

All in all, I'm happy with the results. It's just takes some extra attention to make it work smoothly.

[ramv]

Probably more of new, not broken in parts.

[rodeo guy]

Thats what we suggested as first, but the front third member is used, pulled from a junkyard. :confused:

[zutrooper]

ANdre: I meant to ask...it seems to me that your xfr case would take the beating rather than the front diff. Did you check temp on xfr case.

[Andre75]

Did you check temp on xfr case.

I did not:confused: I'm probably going to change the diff fluid and transfer case this weekend just to make sure there's no shrapnel in there.

I think I'm just going to have to get used to doing the majority of the trail in 2HI or 2LO, and only locking the hubs when it's needed.

[Nazrat]

Just a thought: the front gears might still need a break-in period. I don't think that 4.77s weren't ever in any SOTF trucks so yours may actually not have many miles on them at all.

-Tad

[Andre75]

That thought occured to me as well Tad. I probably put more miles on those gears last weekend than they ever saw in the stock vehicle. I think I'll pull the rear driveshaft and see how everything sounds this weekend.

[Andre75]

Well, before I drained the front diff, I took it around the block with the hubs locked. I've got a bad squeeling that persists above 5mph :confused: .

I noticed the squeeling intermitantly on the trails the other weekend, but I seemed to go away before too long.

Sounds like a bad bearing:barf: , but should that account for the heat? I re-used all my stock bearings after a good cleaning and inspection. Probably should have gone ahead and replaced them all :rolleyes: .

I drove for maybe 1.5 miles at up to 40mph tonight, and the diff was barely warm.

I did get around to changing my rear diff fluid. When I got the cover off, I noticed some discoloration of the ARB. Kind of a level line where the the fluid would sit.
http://216.77.188.54/coDataImages/p/Groups/202/202463/folders/213062/1728593ARBdisco.jpg

Any cause for concern?