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Thread: Diff cooler: Overkill or good idea?

  1. #1
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    Diff cooler: Overkill or good idea?

    The current model Camaro has a differential cooler:

    https://www.hotrod.com/articles/fift...e-2016-camaro/

    I know that long ago Winston Cup cars used diff coolers, too, but theirs simply cycled the diff oil itself through a cooler using a pump driven off the drive shaft with a little belt. The Camaro cooler uses an internal heat exchanger with transmission fluid cycling through it.

    I suspect the only time you'd need such a cooler is if you're planning to spend an hour far above 100 mph. So, overkill for a street car? Or a good idea? It's a fairly simple project to add the Winston Cup type to pretty much any diff, screwing fittings into the fill and drain openings and plumbing them to a pump and cooler.

    Thoughts?

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    edwardb's Avatar
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    Overkill for a street cruiser.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014.
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    Build 3: Mk4 Roadster 20th Anniversary #8674. 03 of 20. 2015 crate Coyote, 2015 IRS. Legal 04/18/2017. #8674 Build Thread
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  3. #3
    Senior Member Fixit's Avatar
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    Overkill...

    I just spend last weekend at BIR with my '65 El Camino - over two dozen 15 minute track sessions varying from 45 to 125 mph on a 50K mile, 53 year old 10-bolt. Engine oil & trans coolers yes, diff cooler no.
    John D. - Minneapolis 'Burbs

    1965 El Camino - LT-1, 4L60e, 4wh discs, SC&C susp.
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    So, you guys are convinced that the diff cooler on the Camaro is a gimmick?

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    edwardb's Avatar
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    Quote Originally Posted by Kirbert View Post
    So, you guys are convinced that the diff cooler on the Camaro is a gimmick?
    No. Production vehicles undergo thousands of miles of testing in extreme hot and cold environments and are sold not knowing how or where they're be used. A big generality, I realize, but likely far beyond the conditions where we drive these cars. Not to mention, as seen in the pics, the exhaust pipes are extremely close to the diff. Obviously during this process they determined to go with active diff cooling. Automakers are, needless to say, very cost conscious. They likely wouldn't have it if it they didn't think it was required.

    Back to the question at hand, I've seen diff coolers used on track specific builds (like John George's) but never on street cars, and don't remember a single report of any issues. I've personally never felt the need on my builds, and can't point to any issues. But I admit I don't drive mine that hard. That was the basis of my response. You asked, I answered. But if you want it, go for it.
    Last edited by edwardb; 08-09-2018 at 01:10 PM.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014.
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    Senior Member Presto51's Avatar
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    This video might help to explain some of GM's thinking on the rear diff cooling.

    http://gmauthority.com/blog/2014/03/...erbelly-video/

    Ron
    "May you be in heaven a full half hour before the Devil knows you're dead"

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    Seasoned Citizen NAZ's Avatar
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    Before you decide it seems like you would want to check out the temperature the gear oil reaches under sustained load and let that dictate the requirement. Everything you add costs money, increases weight & complexity, and weight impacts performance.

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    Quote Originally Posted by NAZ View Post

    Everything you add costs money, increases weight & complexity, and weight impacts performance.
    And adds potential failure modes.


    Shelby American's rule of thumb for differential coolers was they were not needed until you're running races over 2 hours long.

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    My plan is to have temp sensors for the trans & diff. If I find that coolers are needed I'll add as necessary.

    I don't believe that coolers are necessary for the street - not even close. Nor do I think that they're needed for 20-30 minute track sessions. In all my experience with the original 8.8 IRS and multiple friends with the same diff and many HPDE events there weren't any reported failures, that I know of, related to excessive temps.

    I have 20-25 days of HPDE events, some with ambient temps into the mid 90's. A fair sampling.

    Jim

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    The 2016 up Mustang IRS had temp sensors and tend to show high diff temps after 20-30 min on track. But....the exhaust on the 2015 up Mustangs runs underneath the diff. Heat rises so that could be a contributor to the heat also. I always ran BG diff oil in my Mustang and never had rear diff temp issues. Probably not gonna see problems on the street but be aware it is a possibility.
    If in doubt......flat out-Colin McRae

    Coupe #485

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    Per TNcoupe's note.

    It is possible that in the Mustang, with a close exhaust and more ground effects than either a roadster or Daytona Coupe, more heat is retained due to decreased airflow under the car and around the diff. There's a lot of air space around the new FFR IRS, whether it's moving needs to be evaluated.

    At the same time I believe I saw higher than expected diff temps from John George's track videos. Would be interesting to know how quickly the temps went up. HPDE sessions are usually 15-30 minutes, things may not cook in this limited time. An endurance race is a different story.

    There are many design and usage parameters that need to be considered.

    Jim

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    Ford and others use a more deeply finned diff cover to help with temps on high performance models. BMW M cars have them. I put one on a 1995 M3 and put on a temp sensor at the same time. Never got hot enough to worry about even during long track weekends. Ford makes a deep finned unit for about $150 used on the GT 500. I have one on my Cobra. Try that first. There is a story oft told of a Shelby incident with a Daytona coupe. Driver never switched on the electric pump to the diff cooler, it overheated, brought into the pits, oil "bubbled" out, caught fire in the pits and put out. I have seen some video of it as well. I even think that Shelby helped put it out. Some Daytonas had a diff oil cooler vent within the rear "dish" about 6 inches tall by 16 inches wide. Usually messed over. Usually placed where license plate was put on right side, lower quarter.

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