I purchaced a 7 5/8 10 bolt with disc brakes to replace the borg warner9 bolt in my formula. My question is what posi unit do I need for this rearend I have a set of 4:10 gears for it but I want it to be a true posi my motor is pushing 450 hp and spraying it 150 with a 700r4 and 3000 stall. I would apriciate all advice thanks

 

4.10 and 700R4 is a bad combination. The 700R4 has too low a first gear.

Converter stall speed depends on the cam grind. Too high can be just as bad as too low.

If you search through the forums, you'll find many suggestions on posi types. Read through the sticky at the top of the forum for all the information you need on the 10 bolt.

Don't expect the 10 bolt to last though. No matter what you do to try and beef it up, the tiny ring and pinion teeth will always be the weakest part of the diff. Start budgeting for a better diff before investing a lot into what you currently have.

 

What rearend would you recomend alky I don't have a lot of money in the 10 bolt and really just trying the waters with it so to speak so ill know what works with what I have before spending a lot on different rearend. The car has 3:42s now and there not near enough for the car. This motor does not like being below 3000 rpms at all. The car is not a daily driver I have a set of 3:73s also but I was told there wouldn't be much of a difference in those and what I have now.I'm new to all this rearend and gear thing so ill take any advice I can get

 

The Eaton Posi is a good differential. The Yukon Dura Grip is also good for a little less money. A Eaton Truetrac or Torsen will also work, but I like the others better. Stay away from Auburn and Eaton Governor Lock.

Be sure to get the correct series differential for the gears that you have. If you have standard gears then you will need a 3 series differential, but if you have the thick gears for a 2 series then they will not work on a 3 series.

 

+1 Gets my vote too. ( best of the 10 bolt POSI units, requires 28 spline axles )



Not sure how long ANY 10 bolt is going to hold up to that much power.......

 

The Eaton Posi is available in 26 and 28 spline, but the 28 spline upgrade is recommended.

 

I learned somethin' New today !