Differential Cooler Plumbing Question

[James OLC]

I am trying to finalize the plumbing for my rear end cooler and, having received conflicting advice from a couple of manufacturers, would appreciate advice from those who may be experienced with similar setups. The car is being built primarily for ORR events and the One Lap and is utilizing a strange 9” housing with an aluminum center section and Black Gold differential. Packaging is slightly complicated as I am using a 3-link (Lateral Dynamics) setup and between the housing mount for the upper link and the cross-member where the Watt’s link is mounted space is at a premium. I am using a Tilton external pump (mounted on the output side of the cooler) and right now am considering having the pump thermostatically controlled.

The specific issue that I have not been able to get a clear answer to is regarding the “return” side of the cooler and whether it is preferable to have the cooled fluid directed towards the ring gear or towards the pinion side of the assembly.

I spoke to a respected NASCAR transmission/rear end supplier (who advocates internal pumps) and his advice was to direct the cooled oil straight onto the ring gear; their opinion is that this provides the maximum cooling benefit.

I also spoke to a respected rear end manufacturer who recommended directing the fluid toward the pinion bearing as they have observed what appeared to be a reduction in backlash when directed at the ring gear. They did include the caveat, however, that they have very limited experience with running external coolers (and road racing type applications in general, as their market tends to be directed towards drag racing).

DPI didn’t express a preference but deferred to the rear end manufacturers’ recommendations.

Here are the options that we are considering:

1. Top of the housing directed towards pinion gear side:

https://static1.pt-content.com/images/pt/2008/04/pinion20side201-1.jpg

https://static1.pt-content.com/images/pt/2008/04/pinion20side201a-1.jpg

2. Still directed at toward the pinion side but on the “back” of the housing (at least as far “back” as the Watt’s link cross-member will allow:

https://static1.pt-content.com/images/pt/2008/04/pinion20side202a-1.jpg

3. Top side directed towards the ring gear side:

https://static1.pt-content.com/images/pt/2008/04/ring20side201-1.jpg

https://static1.pt-content.com/images/pt/2008/04/ring20side201a-1.jpg

Any suggestions or options. Tech in general on external diff coolers seems to be limited so it nothing else perhaps we can shed some light on the topic.

[HarleyR]

I would say having the fitting directly on top of the housing wouldnt be that good..If you could put it just below the watts link bracket that would be better...you want it to spray directly into the mesh of the ring and pinion... not just on the ring gear.I would assume you talked to TEX racing the invertors of the internal pump...You can do like Roush does and tap the 3rd member its self and install a pipe to -8 fitting that sprays directly into the mesh. best way I can describe it is its located in the first web above the pinion support I would stronlgy reccoment a -8 vent line Inner Seals It inner axle seals.

[chicane67]

Sell the Strange third member... and get the Williams unit. It will make plumbing and all else much easier.

Secondly... unless you are dealing with something mechanical... there is no way to reduce the back lash with the lube alone. You will only increase the amount of lube available for film pressure oiling. Which, will also improve its resistance to impact loading.

The Williams unit directs the return right between the two points in question... the ring and pinion mesh... and the pinion bearing support oil feed hole.

I know James... I'd hate to do it twice myself... but doing it right the first time around has been your mantra.

[HarleyR]

The best way I think would be to bite the bullet and find a used internal pump.... It would solve plumbing issues wiring issues and look bad ass... no pick up line on the bottom of the housing to get ripped off or smashed

[CarlC]

I agree with Tom about the backlash. They might be making a judgement based upon the condition of the contact patch since it is not practical to measure backlash in a running unit. If that's the case, it is very difficult to determine if the change is an EHL, mechanical, or thermal cause.

[David Pozzi]

My Hewland transaxle has a hole right above the ring gear for return oil, but it's after the pinion mesh not before. Later RH side covers had a hose fitting and directed return oil before the mesh. I was told not to use this fitting by a former Indy crew guy who said the extra oil flow right before mesh tended to hydraulic the gears apart, increasing lash so to speak. This was on Indy cars going 200+mph.

I don't know that the guy was all that reliable, I think he was just a gofer for the team but something to consider or ask about.
David

[James OLC]

I would say having the fitting directly on top of the housing wouldnt be that good..If you could put it just below the watts link bracket that would be better...you want it to spray directly into the mesh of the ring and pinion... not just on the ring gear.I would assume you talked to TEX racing the invertors of the internal pump...You can do like Roush does and tap the 3rd member its self and install a pipe to -8 fitting that sprays directly into the mesh. best way I can describe it is its located in the first web above the pinion support I would stronlgy reccoment a -8 vent line Inner Seals It inner axle seals.

I did speak to TEX - they obviously advocate the internal pump. This is something that we did initially consider but diesmissed since we didn't want the pump running all the time. Since it is a street driven car, I wanted to be able to get the gear oil up to temperature before starting the cooling pump. The return into the 3rd member is Tom's MW reference. -8 for the vent is way overkill when using todays low foam gear oils; -6 should be plenty.


The best way I think would be to bite the bullet and find a used internal pump.... It would solve plumbing issues wiring issues and look bad ass... no pick up line on the bottom of the housing to get ripped off or smashed

The issue isn't the pump - heck, new they are about the same price as the external setup (or less with plumbing, etc.) but the housing.

[James OLC]

Sell the Strange third member... and get the Williams unit. It will make plumbing and all else much easier.

Secondly... unless you are dealing with something mechanical... there is no way to reduce the back lash with the lube alone. You will only increase the amount of lube available for film pressure oiling. Which, will also improve its resistance to impact loading.

The Williams unit directs the return right between the two points in question... the ring and pinion mesh... and the pinion bearing support oil feed hole.

I know James... I'd hate to do it twice myself... but doing it right the first time around has been your mantra.

Brett's back Tuesday (he was out last week when I talked to them) so I'll call him tomorrow and talk about some options.

I agree with you (and Carl) on the backlash side of things. Seemed odd to me at the time.

Good (bad?) news is that I have a possible line on a Williams third memeber with REM'd gears - right ratio and everything...

[HarleyR]

An internal pump with one of these would kick ass...http://www.vaportrailracing.com/ only needing the cooler when temp requires....it would then bypass back to the gear I have ran one of these for a few years...everywhere from Daytona to Martinsville with outstanding results...You'd like the "Gearzmo"....

[James OLC]

Talked to Bret at Mark Williams today. Very interesting - I'm still waiting for some information but at this point it looks like there might be a killer aluminum strange 9" heading for the for sale forum shortly.