Rear Diff Cover for Cooling..

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
5,890
Reaction score
7,539
Location
DFW, TX
I use Redline Heavy Weight Shockproof gear lube. It is a 75w90 gear lube with a film strength higher than a 250 weight gear lube. Redline says it has micro size ball bearings that prevent metal to metal contact.


Banks's website is down currently but I didn't see a cover from them for the 9.5 sf axle. Fins on the cover do very little unless you have directed air flow like the videos show. They might make it cool off a little better when parked.

You could run an electric pump and a fluid cooler but it is overkill. It's better to just use good fluid and change it as needed.
I think you would. be surpised just how much airflow is there even without directed flow. I popped an input shaft seal in the Express shortly after I put the 4L85E into it. I was rolling about 50 mph. I coasted about a half mile before I could get off the road. I had a huge smoke screen following me. There was not a spot behind the transmission of the frame, under body, driveshaft, rear end, rear bumper and even the back windows that was not absolutely covered in droplets of ATF. The fins themself add surface area and radiant heat exchange from the increased surface area helps.
 

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
5,890
Reaction score
7,539
Location
DFW, TX
You don't need more fluid. And those aftermarket covers which increase capacity, are they flat back style? If so, waste of money and would cause the oil to be overworked as the ring gear is going to throw oil right at the cover & it'll shear, increasing heat generation. Not to mention that radius that the stock covers have helps oil get carried over to the pinion slinger.
More fluid is helpful in controlling fluid temps. When you are flat out like climbing a mountain the fluid itself stays at a lower tempetature during the load spike because of the extra fluids mass and its ability to absorb more heat while staying at a lower temp. Then when you are off the throttle the fluid has time to cool off. Take a camp stove and heat a small pan or a large turkey fryer. I promise it does not take a rocket scientist to figure out the larger pan will take longer to heat up given the same burner BTU output.
 

DonYukon

Dont stop until it sounds expensive
Joined
Aug 9, 2012
Messages
1,114
Reaction score
766
Location
Fayetteville NC
Well if it was overworked it was a GM fault as it was a stock setup at the time that did not have a hitch. It was turning the fluid black even at low mileage when it still had a stock engine and 4L60E. Never made any noise until the spider gears grenaded.
Wait are we still talking about a van? Like a stock Express van? what on earth were you towing? I thought the express vans were all 2500 frames with 14 bolts?
 

DerekTheGreat

Forum Regular
Joined
May 23, 2016
Messages
1,557
Reaction score
1,557
Location
Michigan
More fluid is helpful in controlling fluid temps. When you are flat out like climbing a mountain the fluid itself stays at a lower tempetature during the load spike because of the extra fluids mass and its ability to absorb more heat while staying at a lower temp. Then when you are off the throttle the fluid has time to cool off. Take a camp stove and heat a small pan or a large turkey fryer. I promise it does not take a rocket scientist to figure out the larger pan will take longer to heat up given the same burner BTU output.
Not at the expense of a flat back diff cover.
 

stutaeng

I'm Awesome
Joined
Aug 7, 2019
Messages
3,410
Reaction score
4,348
Location
Dallas, TX
I guess there are 2 cases.

1 is an axle that is likely not overstressed (but still worked hard) during heavy use, but lowering the temperature of the fluid is obviously a benefit, no doubt. The question then becomes: is the cover worth the extra expense? How many more miles while lowering the temperature prolong over fluid changes? 3,000 miles? 5,000 miles? What does that translate into your time and money? I don't know.

2 is an undersized axle that is likely overstressed during heavy use. I don't believe any kind of cover or additional cooler or lubrication is going to help in that case.

As a side question, has anyone actually seen a 14 bolt (9.5 or 10.5) fail? What breaks? I think there are a few examples on the internet, but honestly not really common if I had to guess. What's the actual fluid change on rear axles anyway per the owners manual?

Except for a fluid change on my 10 bolt truck due to a bent axle replacement, I've never actually changed the fluid on my other trucks. I bought them used, high mileage trucks, so POs probably never changed it either. One of the ones with the 9.5 has a pinion small leak...that I've been meaning to get fixed sometime.
 

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
5,890
Reaction score
7,539
Location
DFW, TX
Wait are we still talking about a van? Like a stock Express van? what on earth were you towing? I thought the express vans were all 2500 frames with 14 bolts?
A 12ft utility trailer is the only thing it ever towed with the 8.5 still in it. Maybe 3,500 lbs behind it max. It was overheating the fluid moving only the van. Then again it was a good 6,200+ lbs empty and often got cruised at 80-85 even 90 mph in the middle of Texas summers on a 105°F day. The stock 4L60E only made it 38K miles. 1997 Express G1500 conversion van with the 245hp 5.7 Vortec.
 

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
5,890
Reaction score
7,539
Location
DFW, TX
Not at the expense of a flat back diff cover.
Wish banks made their cover for the 10.5 as I would own one but they only do them for the 11.5.

After 2 hours towing the travel trailer the 10.5 was running 275°F prior to the large finned cover. Dropped 50°F with the cover and added fluid.
 

DerekTheGreat

Forum Regular
Joined
May 23, 2016
Messages
1,557
Reaction score
1,557
Location
Michigan
...As a side question, has anyone actually seen a 14 bolt (9.5 or 10.5) fail? What breaks? I think there are a few examples on the internet, but honestly not really common if I had to guess...

I have. All of the 3.73 G80 9.5 14 bolts I've inspected at treasure yards to replace my 10 bolt have been locked up. The latest must've just ran dry- either axle spun freely but the pinion was locked solid. Other ones I've seen had chipped teeth or RTV schmoo all over the cover. So sadly in my case, I have not been able to find a good 14 bolt. All of the 10 bolts I've investigated have at least passed visual inspection, which is the inverse of what the internets say I should be seeing.
 
Top