set up
set up
Hello Jim. If setting up an 8.5 from scratch, what is a good starting point for pinion shims if one does not have the old gear set? next, the numbers on my posi carrier are 726 these are the only numbers I can find and they are cast in,is this a 2 series or a 3 series? Thanks for the info and keep up the grear work.... Mike
Re: set up
Ok good to see you using the site this will help many others too. 
First if you do not have a starting point original shim use a .038 pinion shim to start and work the pinion up or down as need with pattern depth.
Next 726 and 725 are 8.5 10 bolt posi units
Big thing about these units is that they will ONLY FIT BOLT IN AXLE rear ends. 1971-1976 Skylark, Cutlass grand prix Buick Olds Pontiac rears
726 is the 2 series unit (holds 2.41 2.56)
725 is the 3 series unit (holds 2.73 3.08 3.233 3.42 3.73 3.90 4.10 4.56)
so you having the 726 carrier you will need a spacer to use the 2.73 - 4.56 gears
you will also need to have a bolt in axle rear.
Hope this helps, Jim Mitschke - J D Race
First if you do not have a starting point original shim use a .038 pinion shim to start and work the pinion up or down as need with pattern depth.
Next 726 and 725 are 8.5 10 bolt posi units
Big thing about these units is that they will ONLY FIT BOLT IN AXLE rear ends. 1971-1976 Skylark, Cutlass grand prix Buick Olds Pontiac rears
726 is the 2 series unit (holds 2.41 2.56)
725 is the 3 series unit (holds 2.73 3.08 3.233 3.42 3.73 3.90 4.10 4.56)
so you having the 726 carrier you will need a spacer to use the 2.73 - 4.56 gears
you will also need to have a bolt in axle rear.
Hope this helps, Jim Mitschke - J D Race
J D Race
Re: set up
Are you or anyone out there interested in swaping this posi unit [ 726 ] for a 408 or a 409 unit in equal condition ?? clutches look good and unit has new carrier bearings.... I'll pay shipping to you and tradee pays shipping to me.... My zip is 92584.... Thanks, Mike
Re: set up
We recondition all our units. Never send out used posi units. Just bad news....that was a learning lesson. Story there....
All the 408 unit are worth the most as they fit both bolt in axle and are the 3 series posi units... The 726 and 409 are the 2 series unit we use them for parts for the 408 and the 725 units.
We sell the 408 like hot cakes and I really do not know why as those GM units are really pron to flex with 2 big windows tend to explode or tip the spiders under hard load and no clutches are available from GM to build them and no spider gears either.
just out dated units because GM does not support them with parts.
I always try to sell everyone NEW units which have stronger everything and will have parts way into the future for rebuilding.
Jim
All the 408 unit are worth the most as they fit both bolt in axle and are the 3 series posi units... The 726 and 409 are the 2 series unit we use them for parts for the 408 and the 725 units.
We sell the 408 like hot cakes and I really do not know why as those GM units are really pron to flex with 2 big windows tend to explode or tip the spiders under hard load and no clutches are available from GM to build them and no spider gears either.
just out dated units because GM does not support them with parts.I always try to sell everyone NEW units which have stronger everything and will have parts way into the future for rebuilding.
Jim
J D Race
Re: set up
Hello Jim. I really do appreciate your info and thoughts on the used carrier situation, that being said , this unit will not see a lot of stress [ torque ] it would just be nice to have two legs rather than one.............. Thanks, Mike