Diff Covers - testing

[Bill Strong]

As we are getting ready to tune the Opel GT to over 100hp, I was looking at ways to keep the diff fluid cool. As I don't have much of my 75 points left, I did some searching and discovered this.  

 

Part 1

 

Part 2

 

 

part 3 - whats going on inside

 

 

 

[pintodave]

Cooling fins... eh maybe.

 

You need more fluid capacity.

[karman1970]

57 minutes ago, pintodave said:

Cooling fins... eh maybe.

 

You need more fluid capacity.

 

I read somewhere once that cars with IRS rear ends often need an external cooler when road racing because the fluid is all confined to the diff housing, whereas a traditional solid axle car can usually get away without one because the axle housings also contain some fluid. Thus, more volume of fluid and area away from the heat source.

[Bill Strong]

8 hours ago, pintodave said:

Cooling fins... eh maybe.

 

You need more fluid capacity.

 

did you hear how more fluid actually caused temps to go up?

[Black Magic]

I would think the quality of your gear and bearing fit would have the greatest effect on gear temp, except the obvious speed and load.

 

Set the bearing preloads well, a little lighter than the "new parts" spec and make sure you pattern the ring and pinion to get it's alignment spot on. This will reduce the heat you create from friction. Then just go race, using a good oil.

 

 

[pintodave]

5 hours ago, Bill Strong said:

 

did you hear how more fluid actually caused temps to go up?

 

Try running only 1 oz then, should stay plenty cool 

 

 

Edit: didn't watch vids yet but I am guessing by 'more fluid' they mean "over filling" the diff. That would make sense. I am not speaking of over filling the diff. 

 

Double edit: I am also not talking about putting a bigger/deeper cover on it to increase capacity, you need to add capacity but keep the extra fluid from sloshing around the diff itself, think like a sump or separate compartment. 

 

Edited September 26, 2018 by pintodave

[Bill Strong]

watch the vids. It's pretty cool

 

[Craig]

On 9/26/2018 at 12:20 AM, karman1970 said:

 

I read somewhere once that cars with IRS rear ends often need an external cooler when road racing because the fluid is all confined to the diff housing, whereas a traditional solid axle car can usually get away without one because the axle housings also contain some fluid. Thus, more volume of fluid and area away from the heat source.

 

Particularly considering what's shown in the videos, I'd think it would have less to do with fluid in the axle housings and more to do with the housings themselves being big heat sinks that conduct heat away from the diff, plus additional area exposed to air flow to reject the heat.

[Ian]

On ‎9‎/‎25‎/‎2018 at 11:20 PM, karman1970 said:

 

I read somewhere once that cars with IRS rear ends often need an external cooler when road racing because the fluid is all confined to the diff housing, whereas a traditional solid axle car can usually get away without one because the axle housings also contain some fluid. Thus, more volume of fluid and area away from the heat source.

 

This sounds like an excuse a solid axle person might make for a reason not to go IRS.

[MoparBoyy]

19 hours ago, SonsOfIrony said:

 

This sounds like an excuse a solid axle person might make for a reason not to go IRS.

 

better excuse is the all extra weight.

[karman1970]

22 hours ago, SonsOfIrony said:

 

This sounds like an excuse a solid axle person might make for a reason not to go IRS.

I believe it was actually in an old write-up for race-prepping C2/C3 Corvettes, explaining why a diff cooler was tops on their list of modifications to make when similar solid axle cars didn't need them.  I guess an iron Dana 44 IRS gets hot in a hurry.  Maybe just mumbo-jumbo the author made up, but that's what it said.

[Craig]

New entry to the series: What's going on behind your flat-back diff cover