Rear Differential Temperature

flatliner · #1 (**permalink**) 05-25-2003, 04:48 PM

Hey guys, what temp. does a Ford 9" normally run at? I'm thinking mine is running too warm. I do have a limited slip diff. After about 60 miles the rear end housing feels very warm, almost hot. I am running a full syn. lube. and only have about 400 miles on this center section. How have some of you guys installed coolers for your differentials? Any ideas on how hot these center sections get? Thanks guys

Tom Kirkham · #2 (**permalink**) 05-25-2003, 09:15 PM

When we run in our diff on a lathe (no load) the temps qet suprisingly hot. Too hot to touch. This is with new gears, aluminum case, Dana 44 gear sets and normal gear oil. All else being the same, a Ford 9 inch will run a little hotter than a Dana 44 due to the pinion running lower on the ring gear on the Ford. BTW lower is stronger but less efficient.

David Kirkham · #3 (**permalink**) 05-25-2003, 11:12 PM

Thomas,

Is there anything automotive you don't know? Thanks for keeping track of the shop while I was gone.

David

Jamo · #4 (**permalink**) 05-26-2003, 12:01 AM

Now if we could just get Mary to weigh in with some recipes...

DAVID GAGNARD · #5 (**permalink**) 05-26-2003, 07:44 AM

Flatliner;

Not sure what temp they are supposed to run at,but mine has been almost to hot to keep your hand on the outside rear center section after a drive of 30 to 40 miles. Talked to a line mechanic at the local Ford dealership and he said that was normal,then went to my dad's house one day after he came home from town and had only driven his F-150 about ten miles and his completely stock 9" was about the same temp as mine,so I guess that is normal.

Have heard from others that they may get as hot as 300 degrees depending on how you drive....

David

Roscoe · #6 (**permalink**) 05-26-2003, 08:37 AM

Remember that the original Daytona Coupes had rear end coolers like an oil cooler.

Roscoe

Roscoe · #7 (**permalink**) 05-26-2003, 08:39 AM

So I guess the next question would be:

If I was going to mount a cooler on a stock 9" rear, how would I go about it? Where would the lines hook up? Where would the cooler mount? Hmmmmm??

Roscoe

petek · #8 (**permalink**) 05-26-2003, 08:41 AM

Ok, dumb question: why do they get that hot? Is it friction between the pinion and ring? How much loss is there in the differential (heat being an indication of mechanicall loss)?

Bud Man · #9 (**permalink**) 05-26-2003, 09:26 AM

All of this being said, would not the Ford Friction Modifier lower the temps a bit?

Bud

Specialk · #10 (**permalink**) 05-26-2003, 09:28 AM

Roscoe,

you would take fluid from the bottom of the diff, then shoot it back in at the top. You would need to install fittings for both. If you have a 9" with a fill plug in the case, you might make a return there.

Junket · #11 (**permalink**) 05-26-2003, 09:42 AM

On the track we discovered the limited slip run lot hoter (200)than the spools and open ones
Ken

DAVID GAGNARD · #12 (**permalink**) 05-26-2003, 11:19 AM

I have seen rear end coolers on NASCAR type cars,they have a small pump sometimes run off a belt on the rear of the driveshaft that pumps the fluid thru a cooler usually mounted under the car near the rear end center section and back to the rear center section near where the standard fill plug is located... A NASCAR related site may have some pictures and info....

Budman;
I run friction modifier in my 9",but it's main purpose is to "smooth out" or prevent "chatter" from the clutches in the trac loc unit...This may also help reduce heat some,but that's not it's main purpose. A lot of heat is generated from the ring and pinion as well as the spider and axle gears.A spool eleminates the need for spider/axle gears,so you eliminate half the moving gears in the rear end and hopefully half the heat buildup...

David

David Kirkham · #13 (**permalink**) 05-26-2003, 07:55 PM

Gents,

We have run quite a few tests and all diffs run hot. You can run a cooler...BUT!!!

I don't think it is required. We have run them for years and never had a probem. Thomas has tracked his many, many times without a problem and he doesn't have a cooler.

Also,

Beware of a differential oil cooler on a street driven car. Tracks are relatively clean, (rocks, nails, assorted crap). One puncture of your oil cooler and you will run out of differential lube. If you are lucky, you will hear the differential going south. You only have about 5 seconds before it COMPLETELY SIEZES. (Ask Lynn Park about his Freeway experience in a Cobra.)

You can not run a differential dry for 100 yards without DESTROYING it. (Just ask on of our customers who forgot to read the "NO OIL IN DIFFERENTIAL NOTE ON HIS WINDSHILED IN ABOUT 5 INCH LETTERS" (He didn't make it around the block on the test drive.)

If you catch a rock in your engine oil cooler, you can generally hear it and look at a gauge and realize you have to shut it down. No such luck with a differential. Siezed differential, (or oiled down rear tires) makes for a real bummer of a day. Blown up engine sucks. Siezed differential and you very well may end up with an unexpected visit to the "Underground Condo."

David

flatliner · #14 (**permalink**) 05-26-2003, 08:17 PM

Thanks Guys this is just the feed-back I was looking for. I guess I just never checked out the diff. temp. in any of my everyday cars and was suprized at how hot the housing gets. I only have about 475 miles on my Cobra and I have been checking everything: Temps on wheel bearings, tranny, engine, coolant,ect. Looking for leaks...found none. Electrical problems....none. Rattles, loose nuts bolts ect. I just haven't had a single problem. What a fun car to drive!!!!
Thanks again guys, Flatliner