Some issues at the track... spining outer tire...

BlackStripes

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Guys,

I had an awesome weekend at Summit Point this past weekend, with a TON of track time ... and I really mean a lot of track time. Also, I just changed my gears to 3.73's because I lost 150 rwhp .. :)

After a couple of laps I noticed that my rear end was quite loose ... which actually I felt during my previous event. To be honest my front is unreal how it hooks which made me thing that was normal.

Well, last weekend the more I drove the car, the loser and loser my rear end was getting (which I started to thing was due to my tires) but at certain point I started to notice that my outer tire was losing traction for a sec and then grab again upsetting the car ... which I find extremely hard to believe is even possible. Anyway, this was more evident in really tight turns. Any ideas?

BTW, I have a 2000 Gt with an IRS with stock diff with around 50 track events and 275/315 BFG Rivals :)

thanks,

Hector
 

LargeOrangeFont

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When did you drain and fill the diff last? It sounds like your diff is toast, and I'd expect that after 50 track events.

Was the car unloading and RPM rising when the tire spun?

Do both tires exhibit the same behavior, or is it all one tire?

If it is all one tire you may want to give the entire suspension a once over, even try to cycle the suspension it to make sure nothing is binding.
 
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Sirl

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How much hp is the car making now? Doesnt really matter, but just curious.

My 2000 GT only put 260 to the wheels but I had a T2R diff and tracked the car with it for 7 years.

I can tell you that I never, ever spun like that, my rear always felt planted, unless it was the tires.
They are pricey, but if you continue to track the car, I highly recommend
going that route, since it sound like your diff is about done anyway
 

BlackStripes

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Thanks guys for the answers!!

Loose where? Corner entry? Corner exit? Mid corner?
There are numerous reasons for this we can explore.

Basically was happening mid corner.

When did you drain and fill the diff last? It sounds like your diff is toast, and I'd expect that after 50 track events.

Was the car unloading and RPM rising when the tire spun?

Do both tires exhibit the same behavior, or is it all one tire?

If it is all one tire you may want to give the entire suspension a once over, even try to cycle the suspension it to make sure nothing is binding.

Last time the fluid was changed was the weekend prior when I got the 3.73's in. Summit Point is really right bias ... not a lot of left turns, and this was happening only on tight right corners.

How much hp is the car making now? Doesnt really matter, but just curious.

My 2000 GT only put 260 to the wheels but I had a T2R diff and tracked the car with it for 7 years.

I can tell you that I never, ever spun like that, my rear always felt planted, unless it was the tires.
They are pricey, but if you continue to track the car, I highly recommend
going that route, since it sound like your diff is about done anyway

Now the car is putting down around 400 rwhp. I was looking at the T2R but I always was wondering why Ford put the T2 in the Boss 302S ... not sure if the extra $100 would make them steer away from one better part. Is it the T2 more reliable? I know the difference in bias.. but not sure if there is something else different. Also I know that the T2R is like 10lbs heavier then the stock diff.

It's your dif. I know the top autox guys rebuild the dif every 2 or 3 events.

That's what I thought... but wouldn't be the inside tire the one that would spin?
 

LargeOrangeFont

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I agree it is your diff. The T2R also has a clutch in it to keep preload in the diff in case a tire lifts slightly.

I have a Detroit Truetrac in my car, and it is awesome. Slightly less bias ratio than the T2R, but only costs $450.
 

BlackStripes

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I agree it is your diff. The T2R also has a clutch in it to keep preload in the diff in case a tire lifts slightly.

I have a Detroit Truetrac in my car, and it is awesome. Slightly less bias ratio than the T2R, but only costs $450.

That makes sense, I've been reading around and seems like the T2R is quite heavier. Funny, when I had my SRA in my car I had a TrueTrac and I loved it, I wasn't sure if there was one for the IRS. It might be a good alternative because I doubt I would ever lift a rear tire :)

Could also be the outside wheel bottoming out.

Not sure, the feeling was like there is zero power to the wheel... and a sec after... power again. Exactly like a slipping clutch.... but no smell :-D

Other question... so if we have a T2 and a T2R ... what in the world is this : http://www.americanmuscle.com/ford-31spline-88-fr500-diff.html , a Ford version ?
 

LargeOrangeFont

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The Truetrac is the same for SRA and IRS, it works for both. I have it in my IRS now.

The Ford Racing Torsen is just the Ford branded T2R.
 
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BlackStripes

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Sounds good, thanks!!

I've been blaming my rear tires for the extremely tail happy behavior but after this past weekend was more obvious... I am glad that I have an excuse in my head of why I was 4 secs off my old times :lol:
 

racebronco2

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The TR2 also has a problem on tight turns. We are talking about a 30mph turn that is off camber. No matter how i tried i could not get my car to put down the power. LargeOrangeFont know the turn i am talking about. It's on horsetheif mile at the around the 42 second mark. I had to take it really easy to keep the inside tire from spinning excessively. Also when drag racing with the TR2 if you do not have both tires equally wet only one tire will spin.
http://www.streetfire.net/video/horse-theif-mile-112010-part-1_2088978.htm
 

BlackStripes

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To be honest, I am in between the T2 and the TrueTac, I am not fan of complicating things, specially when seems like the T2R is a huge improvement in AutoX (which I stopped doing long time ago). I am emailing both companies and whichever is lighter, that's the one I will get.
 

LargeOrangeFont

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Yep.. I have not had the RX7 to Horsethief Mile with the Truetrac yet.. I want to try it to see what the car does.

I could see a regular clutch LSD being pretty good for AutoX, but the helical diffs are great at speed on a roadcourse.
 
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gcassidy

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Hector, got a shot of your car on track last weekend. Sounded awesome!

IMG_4739.JPG
 

BlackStripes

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Cool pic!!! thanks man! I think the sound of my car is more obnoxious than anything else :eek:

At certain point I was talking to Craig (extremely fast red vert cobra) and he told me that you were there, I looked around and you were gone ..

There was someone filming and taking pics, I talked to him for a sec and he told me that he had a channel in youtube... of course I forgot !
 

BlackStripes

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BTW. I called Eaton and they said that the Detroit TrueTrac weighs 22lbs. Based on Ford's website on shipping weight... I think all are basically the same (T2R is only about 2lbs heavier)

EDIT.

I got an answer from MaximumMotorsports:

Hector,

The only difference is the Torque Bias Ratio. (TBR)
If you are road racing, you should use the TR2. You will probably have to
change your set up a little. As the Torsen changes the way the rear tires
push the front.

This is an answer to a tech question about Torsen differentials.

Question:
I run a 94 Mustang in several of the budget endurance race series. I am
looking at a torque biasing diff for the rear axle. I have narrowed it down
to the T2R or the Truetrac. Please tell me what is better about the T2R that
you sell vs. the Truetrac and which bias ratio would work best. I have read
some things on various forums discussing the T2R and it wearing out. Has
there been issues with the T2R wearing and losing its ability to perform? If
so, what is the lifespan that I can expect from the T2R in terms of hours in
our type of roadracing. The car is a 94 Mustang 5.0 with stock suspension
arms and subframe, urethane bushings, 250 HP, 3:27 RP, 17X9 wheels
w/255/40-17 BFG Rivals.

Answer:
The T2R has a TBR of 4 to 4.25:1. The TrueTrac has a TBR of 3.5:1. Neither
of them have clutches.

A higher TBR is needed if the car is used in situations where the lateral
weight transfer is very high. If the car has 500lbs static on each rear tire
and in a corner it transfers 300lbs to the outside tire, then the dynamic
loads are 200lbs and 800lbs. In this case the differential needs to send 20%
of the torque to the inside tire and 80% to the outside tire. The
differential therefore needs to have a TBR of at least 4:1. If the TBR were
only 3.5:1, then the differential would send 22% torque to the inside tire
and 78% torque to the outside tire. Since 22% torque on the inside tire is
more than 20%, the inside tire is going to start spinning.
The driver will need to reduce the throttle position until the inside tire
has 20% torque going to it. This will make the torque at the outside tire
76%. The result is that the car will accelerate with only 96% (20% + 76%) of
the torque that the first differential could deliver to the pair of tires.

If the car is never going to transfer this much weight from side to side,
then the TBR of the differential can be lower with no downside. The greatest
lateral weight transfer will occur in a slow speed corner with an autox tire
such as a Hoosier A6 tire. The BFG Rival tire is a very high grip street
tire. In a road race situation, I don't think it would require the TBR of a
T2R. The TrueTrac TBR of 3.5:1 is probably high enough.

We have never worn out a T2R in our racecar or in any of our Mustangs. We
can't really give an accurate count on the number of hours, but they have
probably seen more testing than most of our customer's car ever will.
 
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DocB

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BlackStripes,

Perfect timing for you to get in on a group buy of probably the best diff made today, and at a group buy price that can not be beat. I have never seen these diffs sell for other than list price.

Although I run a Torsen T2R Racemaster myself and love it, this diff is even better, and stronger. The perfect road racing diff. Even higher bias than the T2R.

This will definitely cure your wheel spins.

Click on the link below to review the thread on ModFords.

http://www.modularfords.com/threads/217066-Group-Buy-Opportunity

Bruno.....
 

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