Short question: Is that a positraction differential I have in my 1970 GS? I was expecting to see some friction plates and or springs, but this looks like a totally encased unit....
I have a 71' 8.5 with a cone style posi. How much abuse can these take? Should I start saving for an Eaton? Jim/Rott Ps , apology for misdirection//hijack...
I have seen a cone style posi unit in most of the 8.5’s that came under Buick’s. The ones that came under 71-72 Cutlass/442 usually have the clutch units,but I have seen a few with the cones. It was likely due to where the car was built. The cone units can work Ok,depending on what you are doing with it.
The car will see track time. 71' 462 Stock 70' small valve heads Isky Supercam 262 (mild performance cam) TH400 w/ stock converter (for now) 71' 8.5 3.42 gears Foot braking on drag radials ET Streets I think I already know where your answer is going. Jim/Rott
I know there are guys on here that run the OEM cone units at the track,but I would not. You could at least send the unit to Jim and have it freshened up. Make it the best you can,but if you break something in it,there is no fixing it.
What I think I heard was , good luck with the cone style, start saving for a 3 series Eaton. Member Buickrat went thru the rearend before I installed it and basically said the above....Jim
Yah, Lots of people always down the cone units. As with everything hopefully we are getting more technology and making things better and stronger...lol. GM used these cone type units all the way till the end of rwd cars in full size and F-body cars 2002. When the LS came out they started putting torsen units which is what Brian was saying a ture trac... form of torsen type posi. worm gears that are initially control they seem to be the new hot item cause all the SUPER cars Germany , Japan etc are using them - Can not say too much bad about them yet... Will have to see as time goes on a years of miles and punishment are laid (layed) ??on them. I have rebuilt plenty of cone units and they work well - Just one of those deals where people have a preference as to what they want in the rear... true BOP guys will stay with that factory unit and another thing is the old Buick and Pontiac SD unit had four spider and 2 side gears making them handle more power to the side gear pieces than a 2 spider and 2 side gear unit found earlier and way later when the cars did not make any power...lol. Spicer POWER lock units also had the 4 spider gear set-ups and were considered one of the strongest LSD from the factory. 8.2 Chevy, 9.3 olds Pontiac, Dana 44 Dana 60 70 80 Mopar 8 3/4 all used the spicer unit back in the day (example picture) ... geez how do you get pictures up on the site now??? Help... Jim J D
I was skeptical when the Tru Tracs came out,but I have done my best to put them through the rigors as much as possible. I haven’t been able to break one,and I have put them in a bunch of other axles that are not driven nicely. I think it comes down to there are more gears inside the unit to share the load. Less abuse for each tooth. Who knows.
Sounds correct to me - More side gear touches like the super duty Pontiac has 4 spiders and 2 side gears to deliver the power. Also I am sure it is the case being hardened not cast so the flex is held in check... the case has to be hardened too because of those worm gears sliding though the worm gear holes all the time back and forth. Now GMs torsen posi for the 7.625 LS motor f-body cars did not seem to hold up as well as the cases were cast and the bolts were backing out of the cases that held them together. ... Might have been because the 7.625 rear was slightly too small for the LS motors...MAYBE? lol. ya think? Most all Posi units work well on the street... Just the track with stickies and big tires will find the weak links. Also lots of times people are trying to push 30 -40 year old products to the point they are not suppose to be pushed. Jim J D
The real limiting factor is the size of the case. You can only fit so much into that cylinder-shaped object. The inside diameter of the ring gear dictates the maximum size of the case. Then you have to try and stuff parts in there that will hold up.
