I have a Truetrac in my 70 GS Stage 1 with 200-4R, 3.73:1 gears, 8.5 10-bolt with rear discs. I is a great posi and uses regular diff grease without the special lube. It is like an open diff until you need it then it is full on tight posi. Nothing to service, nothing to wear out. I have the standard posi in my 71 GS 350 4-speed and it feels about the same when needing both wheels to turn. I've had clutch posis that bind up in tight turns even with fresh grease and additive.
Take those preload springs out of the clutch posi,and it won't bind in the corners. The clutches will be able to relax when needed. The springs keep pressure on them all the time.
I've had a few different write-ups on this site,as well as others,explaining how to properly tune the posi unit,and to eliminate the preload springs,to give you a better,longer-lasting posi unit. Tom,from Tom's Differentials had an article about this same thing,in Hot Rod,in the early-80's,and has a muti-part video on YouTube,showing how to do this. Anything you get out of a box,or in a factory car,is assembled rather vaguely,for the ease of installation. I have seen some factory units that came VERY loose,and never worked quite right from day one.
I purchased a complete 8.5 set up with the Trutrac so, Yes I would again. I like it and have not had one problem on the street or the track. Except for the first fluid change I'm with Greg, maintenance free is for me.
well i'm happy to hear you like yours also. I have a brand new 8.5 with a trutrac and 3.42 gears sitting in my garage but was having second thoughts about the trutrac since I hadn't heard much about it and figured if I was going to swap it out for an eaton now would be the time to do it. I will stick with it for now and see how I like it.
Put one in my F250 and have not been stuck since. With the open diff it came from the factory with she would get stuck looking at wet grass or sugar sand. Now no problems.
Sorry EVERYTHING WEARS. tHIS IS WHERE TRUE TRACS ARE new to the scene ... Will just have to wait and see how they wear. technical aspect... I would say the true trac units are pretty tough. The case is a forged hardened material as it has to be for the worm gears NOT to eat into the case and wobble out the worm gear holes. If the case were cast...the unit would fail instantly from them sliding back and forth and side loads from the side gear torque. SO - as stated run em and will have to evaluate 10 years from now. lol. really that is the only way to know. We are testing one in my 454 Monte SS 1971... been pretty good so far and it gets slicks and street running and freeway driving etc. No issues yet in 4-5 years... Jim J D Race
True Tracs have been around since the 70's. I was into Jeeps back then and, if you had the money, they were the "Go-To" differential, front & rear, for jeeps. Back then, they were Detroit True Tracs. Sometime since then the design was bought by Eaton. Back then, I never knew anyone who had a problem with them. I know drag racing is different then off-roading so hopefully they will hold up just as well on the track. They didn't make one to fit my military jeep so I used Power-Loks front and rear. They were a clutch-type posi. They worked well with new clutch plates but when the plates wore out, they turned into open diffs.
TORSEN UNITS have been around since 1958... But not in automobile use applications, your talking about the Detroit LOCKER most likely.... true trac for the public came out in the 80's etc. a company Tractech Inc. made them popular which bought Detroit Locker and made the true trac part of the Detroit line of goods ... tractech was bought out by Eaton Corp. Detroit true trac was derived from the torsen type posis with less bias action... manufacturing of the units to the public in the 80's and they were not real popular since they were an unknown and probably pretty expensive at that time and you can find plenty of posi unit in the junk yards too. Detroit lockers we first call NoSPIN There are so many buy outs of these goods it is hard to say when and who created the specific designs out there. Even the internet can not keep up with it all. NOW that is not to say you might not have gotten one from a military or industrial dana 44 or some thing... but it certainly was not call true trac... but might have been a torsen type unit. Detroit locker and true trac were bought out by Eaton corporation in the 2005. that is when Eaton jacked the prices up on everything they purchased Clutch units true tracs and Detroit lockers...IT WAS tough back then ...I REMEMBER it well...almost out me out of business. RAndy's ring and pinion decided to make their own copy of the Eaton Clutch posi as the 30 year patent ran out on eatons unit so that was something that saved us from the crazy higher eaton prices.
The early Yukons were Eatons with their numbers ground off,but did have different internals. Then they started casting their own cases.
