Technical What to expect? Positive Traction/Limited slip

I'm going to install a new positive traction third member into my 1964 Ford Fairlane. It's an Eaton Tru-Trac Differential. It's a geared unit, not a clutch unit so it does not need a friction modifier. The Ratio is 3.80. I'm going a 27.1" tire (G78).

I have never had a car with Limited Slip. You hear all kinds of things...

What can I expect as far as general driving characteristics?
What are some of the cautions I need to be aware of?

 

What are some of the cautions I need to be aware of?

Both Both tires worn out at the same time, from constantly doing burn outs.

 

Just be careful on wet roads when accelerating....Other than that just like driving any other car....

 

I’ve had a limited slip, Traction Lok, Twin Grip, Safety Trac, PosiTraction, GovLock, or whatever else you want to call them in every late model daily driver I’ve had since 2002. All rear wheel or 4wd pickups. All three brands, and the only time I ever noticed them, other than in mud or snow, is on wet roads and heavy acceleration. Just like hemihotrod mentioned above. The rear end will have a tendency to want to “slide out”. If you drive sanely with good tire tread on the rear, you will be fine. This is the only reason I’m hesitant about putting one in my son’s (Little Truckdoctor) C-10.

 

I have one, or the equivalent in the rear axle of everything I own, and in the front of the Wife's car.

They are benign. You just have traction. They have no negative behavior characteristics.

I used to put them in the front of a lot of 4x4 and AWD rigs.

 

I've had the very setup and gears in my Fairlane. The first thing is it is not a limited slip differential that is there are no clutches to slip so the positive drive engagment of both sides is not smooth. Going around corners can be challenging because the true track will engage with the difference in wheel speed, it's much like driving with a spool that engages midway through a turn with a clunk. While driving this on dry pavement can be fun even challenging on wet you can find yourself facing oncoming traffic in a heartbeat. One thing you need to do is keep the rear tires exactly the same size by measuring from the pavement to the rim on both sides and keep it the same distances.
Me personally I would recommend a true clutched limited slip differential with my second being a spool even on the street.

Edit: I do believe it worked great at the drag strip would I buy one for the drag strip, no a spool is so much less expensive.

 

The rear tends to “step out” on snow covered or icy roads, especially going uphill.

Nothing alarming, though.

 

He's going to use a Tru Trac not a Trac Lok. Big difference between the two. He will love the Tru Trac.

 

It is indeed, a limited slip differential, a fully automatic limited-slip in fact, and your description is inaccurate. In fact, your description is more accurate of a spool or locker rear diff than a TrueTrac.

From Eaton's website:

The Detroit Truetrac differential operates as a standard or open differential under normal driving conditions, allowing one wheel to spin faster or slower as necessary. When a wheel encounters a loss of traction or the terrain changes, the gear separation forces take effect and transfer torque to the high-traction wheel. The helical-shaped gears mesh with increasing force until wheel spin is slowed or completely stopped. When the vehicle exits the low traction situation, the differential resumes normal operation.

Check out the video at the link, pretty cool and informative... (scroll down)

https://www.eaton.com/us/en-us/cata...DPlRzKbmuV-8WLSpnGpdx4i8nf9AuuvBoC3sAQAvD_BwE

I've installed TrueTrac diffs in a half dozen builds and have been happy with all of them. Will continue to do so.

 

Don't know if you get any snow or ice but if you do with a peg leg the non spinning wheel tends to keep the rear from sliding sideways. With any "locked posi, trutrac etc" with both wheels spinning the rear of the car will tend to go to the right because there is not the drag of the non spinning wheel to keep it straight.

But it really doesn't matter as long as you know what to expect. One year I spent a month out of state at a Bomb Tech school and to say I was anxious to get home to see mama again after a month.

Well wouldn't you know I fly back home and we are in the middle of a hellacious blizzard that had already dumped a foot of snow and the plows are even having trouble getting around and keeping up clearing the roads.

Well the shortest route home is country roads that are HILLY and not yet plowed. I was driving my undercover OT 5.0 car with the trunk stuffed to the gills with bomb stuff and SWAT gear.

I start off cutting trail through a foot of fresh snow and I find the rear is kicked out to the right and it's like those "drifting contests" but it's MAKING PROGRESS.

Come to the first BIG STEEP HILL and what the hell it's not my car and gunned it to get up some speed and downshift the 5 speed into second and drive right by 4wd jeeps stuck on the side of the road and a bunch of regular cars. Good thing there was no traffic coming down the hill as I was passing a bunch of cars stuck in the right lane of a two lane road and I was drifting right by them.

Well get to the top of the hill and have to keep drifting as the snow is so deep and it took me an HOUR of wheel spinning drifting most of the way in second gear the only thing that caused a bit of worry is the temp gauge creeped up to the middle of the range and stayed there. BUT I MADE IT HOME

 

Been wondering about this for some tine. I have a lightweight, long wheel base pickup with clutch type limited slip that exabits this behavior, mostly when accelerating out of a wet corner. Rather severely if I'm not careful. Non of my other limited slip vehicles do this (without trying ). Without the limited slip perhaps the inside tire would just spin without stepping out, no idea.

 

Tru Trac has a reputation for smooth transition in operation. It's done with meshing of the gears. Nothing sudden happens. If you're looking for pucker factor, try a Detroit locker!

 

Got one in my Falcon…can’t tell a difference between it and the stock non posi into that came out of it, except when you flash the converter and let it rip…

seriously you won’t know it’s there…unless you wanna know it’s there…if you know what I mean

 

Only time I got surprised by a posi-, I was crossing the Ohio River on a steel grated deck bridge, in the rain.
Goosed the BBC just a touch, next thing you know I was looking up river!
Normal circumstances, you never know it there (until you nail it).

 

I run a Quick Performance Trac-Lok clutch-type posi in my Ford. One of those things you don't know is there until I go around a tight 90 degree corner and it gets a little noisy for a second.

 

The Eaton unit was maybe $130 more and the Detroit Locker was$150 more. I should have gone with the DL, I have had them in the past and liked them. The last was in an OT '68 Mustang with a light rear, I had to be careful with it in the rain.

 

Icy bridges a gamble. I have an electric posi now and it is great.

 

It's the only way to go. I've logged well over 100k miles with them.

 

I'd be more concerned with the RPM's , do you have an overdrive trans in this car ? Otherwise you'll be looking at 3300-3400 @ 70 MPH. Not real conducive to extended freeway driving.

 

I can’t comment on having one in the rear but have had one in the front diff in an ot vehicle for a long time and love it. On the beach and snow the extra traction is great and the fact that it works like an open diff around turns makes the handling all that much better. Especially in the snow. GM uses a similar setup in the trucks and They can get a little noisy when they lock up under power. Anyone with the tru track get that on the rears ?

 

I have the Eaton Tru/Trac with 3:00 gears in my coupe and couldn't be happier. Does dance to the right when spinning the tires but that's part of the fun.

 

Both wheels push the car IF you're going in a straight line & one wheel doesn't loose traction !

 

We've become so conditioned to think that 1500- 2000 rpm , in the newer OD vehicles , is the "correct" cruise speed we forget that for many , many years 3000 plus was the normal cruise rpm , burned a " bit" more gas , otherwise , didn't hurt a thing . I think an engine sounds/ feels "right" cruising @ 3000+

 

2OLD2FAST is correct, people seem to forget that these cars were driven a long time without overdrive, My Fargo goes down the Road at 3000rpm and doesn’t bother me a bit.

 

Seems to me that some clarification is needed here. It's not like limited slip differentials will automatically cause your car to lose traction in wet or icy conditions and spin out. In fact, it is twice as likely to NOT lose traction under those conditions.

 

They work on the principle that a worm gear can drive another gear but a worm gear can't be driven.

 

Well....you kind of have to think about how traction affects driving. If one wheel is allowed to spin, but the other is not, you will be more likely to maintain side to side traction, but lose forward traction. If both wheels are connected so they both spin, you're more likely to lose side to side traction, but keep forward traction. As long as you are aware of how this affects the car's handling on slick roads, you'll be OK. If you aren't, and you goose it while going around a curve, you can end up in the ditch with a limited slip rear, while you wouldn't with an open rear.

 

Blues, I was just going to say that…or close! The reason a car gets loose , with any traction enhancer, is when you nail it , both wheels spin so there is nothing achoring the rear of the car! It may go left or right or stay straight , depending on ,mainly, road conditions!
There is no magic in any of them…. all traction enhancers just attempt to have both wheels turn at the same speed. Some do that better than others.








Bones

 

Well said!






Bones