[Fot] IRS diff overheating

Wed Jun 3 01:32:55 MDT 2015

I got a diff cover with really big fins from Racetorations (Darryl
Uprichard) some 10 years ago and it's a big difference in cooling and oil
capacity. In 2011 I ran a new 1:4.33 crown and pinion, and this diff cover
was mounted, yet the diff oil got very hot and escaped through the axle
seals. Since then I use to check the T° of the diff casing after races and
practices. I ran 4.1  /  3.9  /  4.33  / 4.55 ratio's since 2011 and
experienced so far that the crownwheel/pinions in the diff housing made up
for most of the T° rising. With an original old Triumph 4.1
crownwheel/pinion the diff housing stayed really cool. Worst is my 4.33
ratio.
I suppose, the friction between pinion and crownwheel, and hence the heat
generated, can be very different depending on manufacturing, assembling of
the parts, running in of the diff..
Marcel

  _____  

Van: Fot [mailto:fot-bounces at autox.team.net] Namens Bill Babcock
Verzonden: woensdag 3 juni 2015 0:32
Aan: Keith Files
CC: FOT
Onderwerp: Re: [Fot] IRS diff overheating

I don’t know if you’ve seen the diff cover on Peyote. I don’t remember where
I got it, but it sure solved my diff overheating problems. If nothing else
the sheer mass of aluminum helps, but it’s deeply finned. I’ve put temp
sensing paint on it a few times and the outside of the cover never gets
above 170F. the cast steel banjo never gets above 180F.  I doubt the oil
gets much above 250—there’s none of toasty sulfur smell when I drain it.  

On Jun 2, 2015, at 2:19 PM, Keith Files <keithfiles at btinternet.com> wrote:

We use a diff cooler to avoid the problem on the TR6, a lot cheaper than
continual rebuilds of the diff. I ran with one doing 3 hours of the
Nurburgring Nordschleife a couple of years ago, it worked perfectly.

Keith

Sent from my iPad

On 2 Jun 2015, at 20:01, Kas Kastner <kaskastner at gmail.com> wrote:

I had failure of all three cars at Sebring with the IRS cars. In practices
the diffs overheated and puked oil out the breather tub as you describe. I
laid part of it to a new diff but most to the heat generated by a disc type
limited slip. The capacity of the diff is marginal for endurance running.
Add to the  capacity or add a cooler. 

Never be beaten by equipment.

On Tue, Jun 2, 2015 at 10:40 AM, Greg And Alison Blake
<ablake2 at austin.rr.com> wrote:

Some of yall may have followed the social Media posts provided by our
teammates through the weekend. We were racing the Beanitos TR6 this past
weekend at what was to be TWS's last ever race. It was a split 16 hour
endurance race (Sat&Sun).

We had a strange failure on Saturday. About 6 hours in, the truck was full
of gear oil. I had routed a diff vent line to the trunk. Upon returning to
the garage, we discovered melted poly diff mounts. Pic below.

I've been scratching my head on this one. Prior to boiling the diff fluid,
we had zero leaks in the freshly serviced diff. I had replaced all seals and
filled with STALUBE 90WT GL4.

I've been racing my TR3 using this same diff fluid for 6 years (replaced
every two weekends). Never a problem with my vintage race car. Of course,
I've never run the 3 for 6 hours straight.

Some of the more seasoned endurance racers asked what fluid I had in the
diff. All suggested that mineral based fluid is not a good choice for
endurance events.

I'd love to hear opinions as to the route cause of our failure and more
importantly, suggested remedies.

As to the results, the car was running consistently 2:1x laps with a fast
lap of 2:10. We ended up taking the workers choice award. Had we run w/o
diff failure and a subsequent battery failure, we could have been in the
hunt for a podium finish. Fastest lap in our group was 2:09.9

Great weekend

Thanks
Greg
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