Hot front diff- drivers side... WTF

So here’s the story-

Pulled my rear driveshaft to evaluate some vibration I’m having and drove 40 miles to work on the front driveshaft (most of it highway- 75mph or so)
Well, most of the vibes are gone- but when I got off the highway I could smell something “hot” Pull into the lot at work and got underneath the truck- diff is awfully hot on the drivers side. Passenger side cooler. Could it be friction caused by my ECGS bushing? Gear oil is old but was replaced with M1 synthetic. I’m shaking my head.

 

I’ve always wondered if the ECGS bushing would cause extra heat.

Following this thread.

 

Sub'd, curious as well.

 

I mean, obviously the front diff isn’t intended to handle ALL the work (and driving at highway speeds at that) but I didn’t expect this to happen.

 

Honestly, 40 miles at 75 MPH... sounds like that's a recipe for heat with the front diff doing all the work! I'm not going to say I'm shocked.

The front diff/DS isn't designed as if it were a FWD vehicle. Great, for when you bust your rear on the trail and still need to get places, but cautiously and slowly. I wouldn't be driving it like there was no change to the mechanics of how its operating.

The DS of the diff is larger housing the spider gear and majority of the oil. The PS doesn't have as much too it so that maybe why your seeing temp diffs side to side.

 

Did you put enough oil back in after you did the ECGS bushing?

 

Rear DS will go back in as soon as I get home... I’m only getting (the worst of them at least) vibes around 72ish mph so I needed to get it on the highway... 40 miles may have been extreme ‍♂️

ECGS bushing was installed and diff oil changed at around 35k (4 years ago) and I’m now just shy of 200k... so, yeah- oil needs to be changed. But when I did it the level was correct (filled till it was coming out of the fill hole)

 

The ECGS bushing only sees movement relative to the left CV axle during turns or during wheel spin of one of the front wheels.

Diffs normally get pretty warm at hwy speeds, but was it really hot enough to smell? Or were you getting grease splatter from your front driveshaft onto the exhaust pipe, and smelling that?

 

That’s a good question... I’m guessing there was some of that going on... I’m pretty good for over-greasing my universals. Half of the reason I pulled the rear was hoping to find at least one u-joint that had some play. No dice ‍♂️ Almost 200k and they are all good, center bearing smooth and tight.

Put it this way- back in another lifetime a girl I was dating had a Toyota Previa- AWD. On a road trip one day, it kept slowing down till we couldn’t maintain highway speed- she pulls over. Took a minute but I could see the front diff GLOWING RED.... yeah. Gets better- when it was cool enough I was able to access and open the fill hole- all we had on us for oil was synthetic 2t oil... so into the diff it went.

No more issues for the duration of the trip. Relationship lasted only slightly longer than the previa though.

So- my diff was nowhere near as hot as that poor previas!

 

Love me some good story times!!

 

I have driven my truck home from the trails on the front diff twice, several hours each time, because of rear diff trail breakage.

It's a smaller diff. It's not intended to be the primary motive transfer for the vehicle like the rear diff is. It's gonna get hot. You can, with enough stress, cook the bearings and races in the diff doing this.

How much heat is too much? No clear answer. But do monitor for any signs of front diff bearing dysfunction.

 

I've driven home from wheeling on only the front diff. That was 5ish hours at 70 mph. Rear driveshaft removed in 4HI. It's not an uncommon practice in certain situations. Diffs get hot under normal driving circumstances. I would check the fluid level for your peace of mind and if it's all good, I wouldn't worry about it.

 

Gonna have the rear driveshaft balanced and get it back in the truck, my ride home from work will be the last ride on just the front DS... unless it’s an emergency somewhere.

 

And for the love of god replace all the gear oil if it has 165k mi on it... (t-case, front diff, and rear diff)

 

Yeah, it’s well overdue. With the amount of miles I pile on it goes by QUICK

 

FACT: A bushing will generate more heat than a bearing under the same loading and lubrication conditions.

So, you replaced a bearing with a bushing, then are surprised at the extra heat generated by friction. If the housing was too hot to touch, then the temperature of the housing is above 150F (old rule of thumb). This means the internals will be much hotter than 150F.

Once you get the DS in order, I'd suggest at least a front diff fluid change. An inspection of the bushings would likely be a good idea.

 

Just grabbed 6 quarts of M1 75-90, gonna do frt/rear/t-case tonight.

It’s a case of extreme laziness. And the fact that the truck hasn’t asked me for much!

 

Got her home, dumped the diffs and t-case oil. Surprised the hell out of me- 160,000ish miles on that oil and the only one that didn’t come out looking more or less clear was the rear diff.

Not sure if that’s more a testament to Mobil 1 products or to the way Tacomas are put together!

 

The front diff isn't designed to be the primary differential. This is why it is getting so hot!! It is being tasked with carrying a load that it was never intended to carry.

 

i would drain & replace ALL drive fluids at this point bumper to bumper

bout time anyway.....right ??