Guys:

For whatever reason, I decided to check rear diff temps after installing a welded 3rd. After 10 miles of driving, the diff is not scalding hot, but it is uncomfortable to touch for more than 10 seconds or so. I don't have an IR themometer to check temp. I'm wondering how hot is normal for a locked rear end. I never really checked the temp w/ the LSD carrier, so these temps may be normal. That said, would temps be expected to be warmer w/ a welded 3rd? Its worth mentioning that I don't think carrier is warped. It did not display any run out, backlash was in tolerance, and gear patterns looked ok.

Heck, I know a lot of guys w/ Nissans (xterra & titans, etc) that have had the paint peel off their rear axle becase of high temps.

Thanks,

Mark

I think you pretty well answered your own question. "Heck, I know a lot of guys w/ Nissans (xterra & titans, etc) that have had the paint peel off their rear axle becase of high temps."

After having a brand new D60 installed in our Jeep with an ARB I noticed we were leaking a little oil out of the axle seals so checked the diff temp and found it much like yours, too hot to hold your hand on. The Wife and I waited around for 10 or 15 min for it to cool so we could go the last 5 or so miles to home. I got out an IR temp gun and found it around 115* to 120* so didn't worry about it too much after that.

From past experience with mine no real difference from welded,spool,lsd or open on the street. I have seen some higher temps(10*) or so on the trail from the clutches(I think) on the lsd. I've seen around 200* on the rear diff(with spool) of my fullsize in the summer not sure of actual temp on the troopers. IMO

I have found my open rear end with 4.55 gears to run hot. It wouldn't burn my hand but I didn't want to leave it on there either. The higher the gear ratio, I would expect the higher the temps too. I can't say that I have done the touch test with the 5.38s yet.

I wouldn't do the touch test with the 5.38's <img src="/forums/images/graemlins/zombie.gif" alt="" />

When I first got my gears in, it was so hot that it was uncomfortable with leather gloves on, I am pretty sure your skin would just stick to it <img src="/forums/images/graemlins/notooth.gif" alt="" />

Should you put in thicker gear oil with a locked or lower geared axle. Maybe 75w-140 instead of 75w-90.

I would stay with manufacturers recommend oil. Remember, even though we are calling this 'hot' it is not as hot as engine oil and the gear oil is made to handle it.

I can't picture how a locked or welded axle can make more heat than an open one. I would guess the heat would come from the gear contact friction and that doesn't change by adding a locker.

I can't picture how a locked or welded axle can make more heat than an open one.

One could guess maybe the lack of differenal ability would cause a constant, but subtle, amount of l/r torque bias. It would depend on how much cornering you were doing, or even the minor differences in tire height. Figure eights in a asphault parking lot would cause more heat from a welded rear than an open one. And minor tire differences would be corrected with normal driving (left and right turns) and by normal tire scrub, but there is still a minor amount of force exerted on the diff that would not be there if it was open.

While neither of the above possibilites are major problems, they may be enough to cause a bit more pressure between the ring and pinion gears.

My guess is that the temp described is normal and may even be related to the gears going through a small break in peroid to account for the welding and any warpage or reassembly difference from stock. I would also guess it will go away (or become a huge problem) in 500 miles or so. I would suggest maybe changing the oil now and then at that 500-1000 mile mark. Just use the cheapest stuff you can find (Wally World) for this change and then go back to whatever flavor you like. This will also allow for a clean out of any residual crud from the welding process.

Michael

Spatter and crap stuck the gears or bearings will have this result.

Randii