Differential Recommendation

MikeBrally

Registered User
I'm trying to decide between Torsen and Detroit Truetrac gear-type LSDs in conjunction with an upgrade to 31-spline axles. Have been unable to get torque capability limits from either manufacturer. My car is making about 425 lb-ft of torque at the wheels now. It is primarily a street car that goes to the dragstrip occasionally. Which of these diffs will hold up better, or is there a third choice I should consider?
 
I'm trying to decide between Torsen and Detroit Truetrac gear-type LSDs in conjunction with an upgrade to 31-spline axles. Have been unable to get torque capability limits from either manufacturer. My car is making about 425 lb-ft of torque at the wheels now. It is primarily a street car that goes to the dragstrip occasionally. Which of these diffs will hold up better, or is there a third choice I should consider?

First off it will have to be 28spline. Second off if you rebuild your current TL with carbon clutches and a heavy duty S spring you will be ok. That can be done by you for around $100 and some aggravation.

Not saying one of the others will be better..Just saying you can save a bunch of money
 
I'm trying to decide between Torsen and Detroit Truetrac gear-type LSDs in conjunction with an upgrade to 31-spline axles. Have been unable to get torque capability limits from either manufacturer. My car is making about 425 lb-ft of torque at the wheels now. It is primarily a street car that goes to the dragstrip occasionally. Which of these diffs will hold up better, or is there a third choice I should consider?

I would recomend the Auburn Pro over the units you mentioned above. I've been using one in my 93 SC (28 spline) for about 6 years and so far it works great. Looks like this when launching off the trans brake at 3400 rpms. I'm also using stock halfshafts.

http://www.sccoa.com/forums/garage_attachment.php?id=2295&attach_type=full

David
 
I don't know what it is everyone has against the truetrac unit. I guess its because its expensive. When I was looking to upgrade the open diff in my SC,I went with a detroit truetrack because It will improve cornering and will never have to be rebuilt. It was only a $200 more than what a new track locker was going to cost, so by the time you factor in a couple of TL rebuilds its a pays for itself. The truetrac is basically the same idea as the torsen and is $100 cheaper than the FRPP torsen unit and is a little simpler in its operation. I don't have mine installed yet so I can't report on results. There are several others on here (DLF, Ricardo1, and Driller) who have run them for years and, as far as I know, have never blown one up. I don't know how it is now, but back in my off-roading days (20 years ago), aubrn diffs were hard to locate rebuild kits for so I've always steered clear of their products
 
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First off it will have to be 28spline. Second off if you rebuild your current TL with carbon clutches and a heavy duty S spring you will be ok. That can be done by you for around $100 and some aggravation.

Not saying one of the others will be better..Just saying you can save a bunch of money

Where do you the parts that you mentioned Damon?
 
is the true track a soft engage detroit locker? i know i wouldnt want a detroit locker in a street driven car. they are great for four wheel drive trucks that dont see a lot of road use. i think that a locker would be dangerous to drive in the winter. and they are noisy when making turns. we put an auburn in my sons mustang and it works great.
 
XxSlowpokexX,

It doesn't have to be 28-spline if I also purchase halfshafts from DSS. I have a 28-spline Torsen T2 now which has been in the car for 10 years and about 120 dragstrip runs. But, the car didn't make nearly this much torque most of that time. From discussions I've had with Torsen, they think my unit is living on borrowed time, which is why I've been looking into possible options. The new Torsen in the Boss 302 and Shelby GT500 is more durable than the T2, but is not compatible with IRS.

722,

No, the Detroit Truetrac is an all-gear limited slip similar in principle to the Torsen. I've been trying to learn whether it can withstand more torque than the T2, but so far have found no comparative data.
 
I hate torsens they are junk. I wouldn't put one in my 4cyl ranger if someone gave it to me. Detroit tru-track units are nice but I still prefer the OEM trac-lok units. Cheap, easy and reliable. If you are using a used one make sure to put a new cross pin and S-spring in it.
Alan
 
XxSlowpokexX,

It doesn't have to be 28-spline if I also purchase halfshafts from DSS. I have a 28-spline Torsen T2 now which has been in the car for 10 years and about 120 dragstrip runs. But, the car didn't make nearly this much torque most of that time. From discussions I've had with Torsen, they think my unit is living on borrowed time, which is why I've been looking into possible options. The new Torsen in the Boss 302 and Shelby GT500 is more durable than the T2, but is not compatible with IRS.

722,

No, the Detroit Truetrac is an all-gear limited slip similar in principle to the Torsen. I've been trying to learn whether it can withstand more torque than the T2, but so far have found no comparative data.

DSS says to use cobra half shafts if going 31 spline and they you are still stuck with stock outer splines which are the weak link. So your talking at least $2,000 to put shafts and a diff in a car that will do well with just a good trac lock build. Youre option. Also the cobra shafts are shorter and Im not so sure how that will play out durability wise


Ralph. You can get these from summit. Heavy duty S clip and carbon fiber clutch kit. Works amazingly great
 
I vote for the Detroit True-Trac. Very street friendly and always dependable at the track with straight launches.
 
DSS says to use cobra half shafts if going 31 spline and they you are still stuck with stock outer splines which are the weak link. So your talking at least $2,000 to put shafts and a diff in a car that will do well with just a good trac lock build. Youre option. Also the cobra shafts are shorter and Im not so sure how that will play out durability wise

From what I've read, the aftermarket 31 spline stub shafts are junk. They arn't any stronger than the OEM 28 spline ones and OEM's are no longer available

I think XR7Dave tried to convert a pair of Tbird shafts over to 31 spline and encountered problems
 
Ralph. You can get these from summit. Heavy duty S clip and carbon fiber clutch kit. Works amazingly great

I'm not sure why you would insist that the TL works amazingly great. I know you aren't much of a drag racer so maybe that's it? On the street a lot of things work "amazingly great". I've had people swear to me that they have a TL when they don't. They seem to think that just because the car spins both tires most of the time, it must be a TL. I know you don't fit into that category, but the point is valid - on the street it doesn't take much to get both tires spinning. A completely worn out TL will spin both tires on the street basically all the time.

I chuckle lots of times when people install an Auburn and then complain that their car won't spin the tires anymore. It makes a difference if you have a solid performing differential as opposed to one that mostly works. Just because both tires spin doesn't mean they both spin at the same speed. Traction is always improved when the diff is solid. How do you know yours is solid? The best hint is to take it to the track and have someone watch you do burnouts from behind. You would be amazed how many people say "but I just rebuilt the TL?!?!"

Which unit you get should be determined by how you drive and what is important to you. If you street drive only, don't mind the occasional rebuild, and want something that is mostly unnoticeable most of the time, a TL is a good option.

A more aggressive diff like the Auburn will bind on tight corners and will tend to push in corners unless you break the rear end loose. It will make noise occasionally and it will generally let you know that it's back there until it too wears out.

If you want something that is completely invisible in all types of normal driving yet hooks up BEST in corners and coming out of them, then a Torsen or Tru Trac is the only answer. They are not junk, but they do wear out and they aren't as strong for drag racing. The difference between a Torsen/TT and a TL in terms of wearing out is that the TL has replaceable parts whereas when you wear out a Torsen/TT you are looking at scattered parts. Drag racing will shorten the life of a gear type differential as this is just not the purpose it was designed for. If you don't launch real hard it will be fine, but if you planning to do 5000rpm clutch dumps, then it's not the way to go.

Another thing that people forget about is the unique shock loads that the IRS sees. If you have a 5spd then wheel hop becomes an important consideration. Be aware that the tighter the diff is, the less likely the car is to wheel hop. Since the IRS is, well, independent, you can very easily put all the load on one side of the car which will result in over compression of that side bushings and exaggerate wheel hop. On the other hand, if the diff is very tight (like a Detroit Locker) then it will force both wheels to put the same forward force on the suspension and will actually very significantly reduce your tendency to wheel hop. An Auburn Pro does this pretty well too.

I'm just saying that there are reasons to choose one over the other and being aware of what the benefits of each are can help you make the right choice. I don't personally like dealing with diff fluid all that much so I prefer to do it once and do it right.
 
I love the smell of gear lube in the morning.... :D

Truetrac.

I've done 5-6K launches for 10 years in my Cobra and haven't trashed it yet. Went through a bunch of half-shafts, but the diff has held up. ;)

Admittedly a lighter car (3,600 lb. race weight), with less than 300 RWTQ, but I run 4.56's and a Viper T-56.

I have a Torsen T-2 (got a deal) in my SC that's doing fine launching at 3,500, and I've got close to 400 RWTQ, but I prefer the Truetrac.
 
I've seen wasted Traction Lok's and grenaded lockers (off-road), but how exactly does the True Trac meet it's demise? Is it pretty much scrap afterwards?
 
I've seen wasted Traction Lok's and grenaded lockers (off-road), but how exactly does the True Trac meet it's demise? Is it pretty much scrap afterwards?

The only broken one I have seen in person was exactly that completely broken. I have seen a bunch of torsen units that way. I have seen OEM trac-lock units that way but they were almost always high mileage. Once the pin wear gets bad and it starts moving the entire thing breaks.
Alan
 
I spoke directly to DSS, and they can provide you with axles shafts the correct length for the t-bird along with 31 spline inner stub shaft, and 33 spline outer stub with custom hub in t-bird or mustang bolt pattern. Nothing from them is inexpensive, and all the above does add cost above the current list. If someone is interested, your best bet is to call them directly to get the details, and then work through one of their re-sellers for pricing. (i.e. D'Agostino Racing or Lethal Performance)
 
I spoke directly to DSS, and they can provide you with axles shafts the correct length for the t-bird along with 31 spline inner stub shaft, and 33 spline outer stub with custom hub in t-bird or mustang bolt pattern. Nothing from them is inexpensive, and all the above does add cost above the current list. If someone is interested, your best bet is to call them directly to get the details, and then work through one of their re-sellers for pricing. (i.e. D'Agostino Racing or Lethal Performance)

that would probably be a $3,000 ordeal. Nice that its offered but it just doesnt seem its needed.... especially for a car with 400ft /lbs tq. $100 bucks or $3,000...hmmm. And I am one to buy everything for my car..Seriously
 
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