True Trac vs Open Diff


Viking with a Hammer
Having owned an Econoline 350 (whale tail version), the Truetrac is the only viable option for a rear diff for that 2wd van. Unless extensively modified, Econolines aren't as forgiving as the trucks are.

A Detroit locker would be perfect if you never, ever, see snow and have tires that are excellent in the rain. But IME, rear lockers oftne make thing worse in 2wd.
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WSS, he drives a 2WD Van. With driveability problems of full lockers, i'd still put money on a True Trac. Another reason is cost. True Trac is at most half the price of an ARB. No compressor, tubing, switches, complicated install, or electrical circuits. I had woes with my front and rear ARB's on my rock crawler. Thick dust, like in the desert was a switch killer. BTDT. Passing weeds, rocks or floatsam would wreak havoc with the air tubing. jefe

'82 CJ-8, NP435, Dana 300/4:1, 4.88 gears, ARB's, Dana 44/Chromoly, Dana 60 Mosiers, 37 inch tires. 130:1 final drive in lo/lo. 142:1 in lo/reverse.

Ohhh, ya my assumption was up front. My bad

VERY NICE 8 BTW! Looks like lots of fun.

How do you like the D44 w/chomoly setup? I'm running D44's front and rear. SM420/D30 trans and tc.
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West slope, N. Ser. Nev.

Jefe's Scrambler as of 01/16. After spending half my life building it, It is sold. I always have a 4x4 project going somewhere. I never broke any drivetrain parts on this rig, as hard as I tried.

1982 Jeep CJ-8, desert sand and Nutmeg, by now all rattle can Sand. AGR power steering box and pump, MORE 1-1/2” forward steering box brackets, Chevy power discs front and Cadillac disc rear, removable 10 watt CB, Full Kayline Nutmeg soft top and full soft doors, (not made in nutmeg any more) windjammer, 1/2 doors and tired bikini top, custom soft cab top, beat up custom rear tonneau cover, removable, fold down rear seat. Room for one more seat behind the rear seat. Rear, swing away tire rack with MT. bike fork clamps. A same diameter but mismatched spare tire on 10” rim. The front half of the frame has been 3 side plated and gusseted.
ENGINE: built for torque. Peak torque: 1400 rpm. Pulls down to 300 rpm with stepper motor disabled.
4.2L I-6 block and crank, with .060” overbore pistons and rings, making it a 4.4L.
4.0L, High Output head with Mopar MPI fuel injection, Hesco adjustable fuel regulator with gage. H-264-14 cam (.470” lift) and Cloyes double roller timing gears and chains advanced 4 degrees, High Volume oil pump, stock ‘95 XJ exhaust header, 2.5” aluminized tubing, cat and throaty 12” glass pack.
Hand throttle, MORE engine mounts. 2-5/8” AutoMeter gauges (0-4K tach, oil, temp, Volt, Vacuum) a rather new yellow top battery.
NP-435 ( Adapter by Advance clocked Dana 300 w/ 5 gear TeraLow 4:1 gears, and Currie twin sticks, (you can have low range, front wheel drive if you want it.) Sacramento Drivetrain drive shafts w/ extra long splines, 6 bolt SuperWinch hubs, (plus a new spare set) u-bolt style u-joints, 130:1 crawl, 65:1 in lo/2nd gear. 142:1 in lo/reverse. Dana 44, 30 spline front, w/ARB air locker, Warn 4330 ChroMoly shafts, custom made ChroMoly steering-over rods with 1 ton TRE’s, Parts Mike steering-over knuckles, CTM bushing outer U-joints, 4.88:1 Dana 60, 35 spline rear w/ARB air locker, Mosier H.D. shafts, 4.88:1. 4XDoctor pig cages
Springs-Over-Axle w/ 6 leaf RE SOA 2-1/2” lift springs with front reverse shackles.. Rancho 9000 adjustable shocks. H.D. shackles. Extra long S.S. brake hoses.
Fenders trimmed to clear 37-13.50-16 TCL ProComp XTerrains on 8” wheels
Extra wide front rubber fender lips. Tired rear fender lips to keep the CHP off your case. Currie steering brace and welded/over boxed front frame horns, Radiator saver.
Stubby 'rockhugger' front bumper, Ford Mutt recovery “D” rings. Roll cage, Wrecking Ball Proof custom rocker panels, "Off-Your-Rocker" steel rear diamond plate quarter panels, 24 gal. steel tank and steel skid plate with exterior fuel pump and filters. You’ll never have to carry fuel cans. On board Premier Power welder (180 amp alternator) which has a battery charging feature and an aircraft style manual throttle for adjusting amps. Class III hidden 2” receiver hitch. Warn #8274 Winch (aka: fastest winch in the west) A big plastic box of spare parts, belts, hoses, u-joints, plus a couple spare driveshafts and spare stock geared Dana 300 transfer case.


New member
I've studied the gear type limited slip units. It looks like they won't work in reverse and act like an open diff?


FWIW the owner of a very reputable diff shop here advised me NOT to go with the Detroit True Trac any longer.
He said it isn't made to the same standards as just a couple years ago, lesser quality materials, tolerances and QC. I "think" he mentioned it being made offshore now also but not sure.
I have a buddy who has abused his dual True Trac'd Scout for a couple decades and they have been great for what they are (he wheels with us dual locked guys all the time and does pretty darn well) and I have one in my Mustang but the newer version he recommends against.

Do some research before laying down the coin.

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Last year, I had a True Trac installed in my 69 Fairlane Cobra with a torque monster 428CJ engine. It has held up flawlessly so far. I don't drive it all the time but when I do, it gets abused often. Your shop owner may be right but you couldn't prove it by me. When I gave the True Trac to the shop to install it, it looked like a very good quality part. I consider that shop a very reputable shop and they had only good things to say about True Trac.
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How well behaved are TruTrac rear ends on the highway in snow or rain? I still have bad memories of the first time I drove my 82 Mustang GT with factory clutch type Traction Lok on the interstate in the snow going up a grade. Suddenly the back end could not make up it's mind which lane it wanted. Only solution push in the clutch.


How well behaved are TruTrac rear ends on the highway in snow or rain? I still have bad memories of the first time I drove my 82 Mustang GT with factory clutch type Traction Lok on the interstate in the snow going up a grade. Suddenly the back end could not make up it's mind which lane it wanted. Only solution push in the clutch.
They act the same. One tire spins and the other tire starts to get torque.
My mustang does the same thing but it's still much better than an open diff. After driving Detroit Locker and limited slip vehicles exclisuvely for the last 34 years it's not a big deal.



I have to agree with Scout. The True Trac operates smoothly without notice. Auto lockers engage the outside wheel around corners by basically an on and off method. I have an auto locker on one of the differentials on my SCCA road racing sports car and it can be a handful in the corners when the track is wet. It can also be kind of jerky when lightly accelerating around sharp corners when not up to speed on a dry track. The differentials for my race car that work more like a True Trac are much more predictable in the corners as long as I don't put too much power to it and break both tires loose.
The best thing about an auto locker is they rotate both wheels at the same speed under power when going straight no matter how much traction is available. This is very useful off-road (especially if one tire is not touching the ground). They also keep both wheels turning in corners regardless of traction available.

Happy Joe

Apprentice Geezer
As soon as Eaton bought Detroit Locker I feared degradation in quality (it happens whenever you get bean counters trying to maximize profit).
Be aware that Tru-Trac is a (Eaton) brand name and other companies make helical geared (Torsen style) "limited" slip differentials.
Also Ford uses/used a "traction lock" clutch style limited slip in many vehicles; Torsen style limited slips seem to be relatively hard to find in scrap yards (at least for Dana axles, Jeep products and Ford 8.8 axles).
I got mine for the D35 IFS in the explorer from;
I will never again use a Detroit Locker on or off road (it tried to kill me too many times on ice).
I also have broken several gov-loks in difficult terrain (some chance of body damage) with 35" tires (not huge).
Tried (because they came in the used vehicles or junk yard substitution axles) many brands/types of OEM limited slips ; none worked particularly well in a dual purpose on/off road daily driver/semi extreme 4 wheeler (tins Torsen is potentially an exception).

For me its ARB (selectable air lockers) or Torsen (limited slips); so far no problems with either... (your experiences may vary).

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