"usual" differential heat

RatLabGuy

RatLabGuy

You look like a monkey and smell like one too
Joined
May 18, 2005
Location
Churchville, MD
I kno this is a hard question to answer - but how hot should a rear diff be after about 20 mins of typical 55-65 mph driving?

I'm chasing down an odd noise, and just realized my back end is quite warm after a test run Mostly just the center punkim area, horiz. portions of sharts are cool... but I can barely stand to touch it with my hand. Fresh 80w90 fwiw.
 
Ive never messed with Toys...but never seen a ford, chevy or jeep that hot...warm to the touch sure...but not painful to touch warm
 
Ok.... so.... what sorts of things cause a hot diff?
I really don't think my root problem is diff-related (at least the noise) but maybe thsi is a good symptom to work backwards from.
 
Caver Dave said:
- Lack of/too little gear oil
- Improper gear setup
- Bearing(s) toast
Amazing enough, the same things that cause "odd noises"! :flipoff2:
Click to expand...

hm...

-new gears from Chase, had same noise on prior 2 3rds - just slowly getting worse
-literally just changed oil (had the 3rd out for fixin ga leak and e-locker wiring issues)
-hmm possible? But seems odd given the behavior, see below

Well I was going to start a seperate thread for this, but here's the deal w/ the noise.

It's kind of like a sliding/grinding sound, ONLY occurs right at the transition point between applying gas and coasting. Auto tranny btw. Pedal firmly pressed - no problem. Coasting - no problem. If I very lightly feather it, like you might going slightly downhill, then it will persist the whole time until either letting off or pushing down to full-on threttle.
Def gets louder w/ speed, at like 25mph it's bearly audible, noticible at 45 and loud at 65.
No vibration, just grinding noise - I can kind of feel it in the floor (at high speeds). It sounds alot like a pice of metal sliding inside another piece w/o lube.
T-case to pinion angles fairly normal.
First noticed it years ago w/ first mild lift on back end, but was very subtle and I choked it up to AALs and shackles offseting pinion angle. It's been slowly getting more andm ore noticible - over that time I've changed 3rd members completely twice and that never made a diference.
No longer using AALS or long shackles.

I can only think 2 possibilities now - output shaft bearings (UGH!) or maybe wheel bearing(s). But I'd expect wheel bearings to be constant?
There was a very slight wiggle in upper u-joint, just replaced it - no change, but did eliminate a slight vibe I was getting)
 
pinion bearing? does it do it in reverse, it may be that when you get on the gas, the pinion angle shifts and causes it to grind and once you actually get into the pedal it settles back into place.

of course, you said 3rds were rebuilt, that would probably eliminate my theory unless the old bearings were reused. i wonder if the housing at the pinion could be warped or damaged.
 
RatLabGuy said:
or maybe wheel bearing(s). But I'd expect wheel bearings to be constant?
Click to expand...


You'd think.....my dads was doing the same thing, replaced the wheel bearing and its cured. You could at least check them to eliminate the possibility. That still wouldn't explain the diff heating up though.
 
The diff in the rear of my TJ (dana 60 FF) was getting so hot I couldn't touch it after running it for a while. Neighbor at the time was an Amsoil rep and gave me some of their synthetic gear oil. Now it will get warm, but is a good 40-50 degrees cooler. I don't really understand how one oil could be that different, but it was. FWIW, I was probably running Coastal 75w90 or something equally cheap.
 
BigRedB2 said:
pinion bearing? does it do it in reverse, it may be that when you get on the gas, the pinion angle shifts and causes it to grind and once you actually get into the pedal it settles back into place.
of course, you said 3rds were rebuilt, that would probably eliminate my theory unless the old bearings were reused. i wonder if the housing at the pinion could be warped or damaged.
Click to expand...

Yes, I've completely swapped 3rds twice (totally different units) since it started, and the latest is all new internals setup by Chase.

lbyota85 said:
You'd think.....my dads was doing the same thing, replaced the wheel bearing and its cured. You could at least check them to eliminate the possibility. That still wouldn't explain the diff heating up though.
Click to expand...

That's my next step - I think it's pretty much the only thing left w/o moving up into the tranny.
Is there an easy way to check them w/o actually pulling out first?

jeepinmatt said:
The diff in the rear of my TJ (dana 60 FF) was getting so hot I couldn't touch it after running it for a while. Neighbor at the time was an Amsoil rep and gave me some of their synthetic gear oil. Now it will get warm, but is a good 40-50 degrees cooler. I don't really understand how one oil could be that different, but it was. FWIW, I was probably running Coastal 75w90 or something equally cheap.
Click to expand...

using 80w90 Coastal - that was just a temp until I knew everything was good w/ the rear and wouldn't have to yank it yet again and waste the spendy $$ on the good stuff.
 
its probably not broke in yet reason for the heat, we set them up very tight and they need to be broken in slow. just drive it, if noise was present with all three diffs unlikely that the diff is the cause. of course if it is we will of course take care of it. im thinking its in your tranny, what the condition, mileage of your tranny.
 
Cperry said:
its probably not broke in yet reason for the heat, we set them up very tight and they need to be broken in slow. just drive it, if noise was present with all three diffs unlikely that the diff is the cause. of course if it is we will of course take care of it. im thinking its in your tranny, what the condition, mileage of your tranny.
Click to expand...

Well the 3rd has a good 500-1000 miles since installed initially, I'd have to look at my records, this last time I just pulled it to address an issue w/ the e-locker and fix a leaky seal. I did notice it didn't feel as tight now as it did when I first got I tfrom you - it was indeed really tight then.

AFAIK transmisison is original - auto, pretty sure A340h, 167,xxx mi and otherwise behaves normally.
Trans fluid a little dark, prob wouldn't hurt replacing but no burnt smell etc and only ~7k old. Last night I drained/replaced t-case fluid for S&Gs, it was fairly dark but reasonably full, that didn't change anything (not surprised).
 
Tonight I tried a fun trick - pulled the rear driveshaft, took a very quick up teh road and back. Nomrally no big deal - except I have a Lockright in the front, lol. Lets just say I'm glad I waited until late at night so nobody was around.
But - no noise. So that at least eliminates the main tranny.
Unfortunately it dosn't eliminate something like the bearing on the end of the tailhousing, or anything rearward that would need some stress on it.

Driveshaft splines into the slip yoke "look" ok at least - there is a very slight amount of wiggle between yoke and main shaft but it's hardly perceptible, at least at full insertion.
Here's a pic:
http://www.4rtoy.rewazule.com/Pics/Driveshaft/IMG_5336[1]
(large for zooming goodness)
i'm a litttle bugged by the marred outside of the yoke, that's righ tabout where the collar end rides now after lift etc.
 
Had the same kind of problem after I changed the transmission in my cj-7 to. It was my rear driveshaft angle. I had to lower my transfer case about one inch.
 
DRAINMAN said:
Had the same kind of problem after I changed the transmission in my cj-7 to. It was my rear driveshaft angle. I had to lower my transfer case about one inch.
Click to expand...

That may be possible - but I just don't get why I'd have thsi problem w/ only like 3" of lift - I've not heard of anybody else having it.

I cleaned up the shaft really well, re-lubed put it back and went for a drive. Still there... although it did seem to take a sec to show up.
However, I grabbed it right at the yoke junction and felt for wiggle - there is a very very slight wigle between the splines of yoke and shaft. Before I assumed this was the upper u-joint.
i'm going to try and bum a shaft from a guy this weekend and swap it out for a temp ride, see what happens.
Anybody know if shafts are the same length ofr auto and 5spd 4Runners?
 
yesterday I went and bummed anotehr driveshaft from somebody swapped it - no change.
also tried adding 4 deg shims - no change but did add slightwoble - prob overshot pinion angle.

Today - RESOLUTION - it's in the rear of the t-case, prob (hopefully) the bearing in the tail housing.
Pinpointed by jacked up rear end, trapping to a tree 9safety) and running it wheels spinning. D-shaft was def resonating it but the source was def farther up than that.

man i just hope it's only in the tail, I really don't want to pull the whole damn thing.
 
Pulled off the "transfer extension housing" checked the bearing just behind the oil seal.
It has a slight amount of slop, but nothing major. Uses rear full sizes ball bearings, unf it's pressed into the housing. I took it by a local good-ol-boy tranny shop, guy was not confident it was was really bad, no sign of pitting or grinding in balls.

I just took a closer look at the shaft where it's coming out of the case end into thsi bit... it has a noticible amount of play, both side-side and in/out., maybe 1/8" or even 3/16 so, hard to tell. Here's a pic
awww.4rtoy.rewazule.com_Pics_Tranny_wo_extension_housing.jpg


Crap, so to me that suggest's something's worn/loose farther in, I think this rear bearing is doing it's job and keeping it even more steady.

FSM diagram suggests I coudl even unbolt the rear of the this case where teh chain gear is, it's prob in there... but I can't get the damn speedo gear off of the end of teh shaft.
it slides out about 1", as shown in that pic, then stops stuck. FSM just says "remove speedo gear" w/ a pic of a hand sliding it off. No set screws or anything I can see... this is keeping me from getting into it. any thoughts?
Suspicious I may just be looking for a replacement tranny. Good thing nobody actually wants the A340h.
 
There`s got to be a slight burr or ridge holding that speedo gear from coming all the way off. Try pushing it back on and feeling around tail shaft to see if that`s the case. It could be right there at the splines. Try running a file on it. Also can use a small hammer (dead blow if you have one)to lightly tap around the gear to get it to slide off.
Maybe time for some 4.7 gears?
 
Why would the transfer case make the diff hot though? One maybe the cause of the grinding noise but the rear diff would only be heated by the bearings or gears?

If the grinding noise (what you are searching for now) has not caused an issue yet, in the last 3 years, you just trying to prevent or?

How near is the exhaust routed by the diff / any chance of reflective heat?
 
SHINTON said:
Why would the transfer case make the diff hot though? One maybe the cause of the grinding noise but the rear diff would only be heated by the bearings or gears?
If the grinding noise (what you are searching for now) has not caused an issue yet, in the last 3 years, you just trying to prevent or?
How near is the exhaust routed by the diff / any chance of reflective heat?
Click to expand...
Caver Dave said:
pwned :lol:
Click to expand...

I'm assuming these are two different issues.
when running on jackstands, noise is clearly coming from top end of shaft/rear of t-case. Buddy there w/ me agreed.
Exhaust is not near the diff.
And the heat is not like rediculous glowing red, just noticibly hot to touch.

The noise has lately gotten louder, but the truck has also grown taller. In 3 years, I have had in on the highway >65 mph only the day I drove up here to MD.
I plan to drive it down to NC, in April and and May, so I need to go ahead and fix it.

Replaced the tailhousing w/ one from a junkyard. Did not fix it :shaking::shaking:, although tone is a little different now.
Tonight I'm pulling the bearings, nothing left.
I agree that would explain the diff heat and the general type of sound, but not why it only happens when torque load is transitioning, and not any other time.
 
Are you refering to the Carrier Bearings, were they replaced with the gear set-up?
 
^^^
could be the angle - you got shims in there still?
I had the same issue grinding noise in between gas and coasting.
Took out the shims from the leafs and problem was gone.

or the outer bearings are shat like was said before.
don't see how the Tcase effects that. those are 2 sep issues.

you said you got the gears from Chase. Okay who put them in?
 
WARRIORWELDING said:
Are you refering to the Carrier Bearings, were they replaced with the gear set-up?
Click to expand...

i'm referring to wheel bearings
Everything in the 3rd is new

Lorenzo816 said:
^^^
could be the angle - you got shims in there still?
I had the same issue grinding noise in between gas and coasting.
Took out the shims from the leafs and problem was gone.
or the outer bearings are shat like was said before.
don't see how the Tcase effects that. those are 2 sep issues.
you said you got the gears from Chase. Okay who put them in?
Click to expand...

Measured pinion angle, from flange to driveshaft is right about 76 deg, making bend 14 deg. It is very close to the same at the top, frame is in the way of seeing it straight on from the side but it's w/in 2 deg or so.
Now only lift is from springs, stock shackles. When I put these springs on, I used no shim. I had some 4 deg shims on hand from earlier so I slipped those on, they're on now. I'd try going back down to say 2 deg if I could find some that small.
Chase setup the 3rd completely, I just put it into the axle. Pretty hard to screw up that part?
 
Back
Top