I am wanting swap out the stock gears and looking for advise on a good product and what is needed to complete the job. Would like to order all the parts and have my mechanic install while I learn. Never messed with drivetrain and asking for serious replies thx.

 

Neither.

What are you planning on doing with the car? 3.42 would be my recommendation, with 3.73 being the absolute lowest.

 

Using on a 1/8th drag.

 

If you proceed with the swap, you may have a 50/50 shot at them lasting very long.

IIRC you have to grind on some of the teeth or pin to get the center pin to fit in place.

 

The 7.5 rear end was not designed for a gear in that range. As the ratio gets closer to the 4.00s the ring gear gets thicker. When you get to the 4.10 or 4.56 the ring gear is too thick to allow the cross shaft to be removed from the differential. You can buy a special cross shaft that has been cut down on one side so that it will slip out far enough to allow the c clips to be removed or installed on the axles. Without modifying the shaft you can not get to the c clips. You can also grind the shaft that you have now, but the original shaft is soft in the center and may not hold up well. If you have a chrome plated shaft then grinding it will allow the chrome to start peeling off and can cause wear problems.

As the ratio gets closer to the 4.00s the pinion head gets very small. This takes a lot of the strength out of the gear and it is much more likely to break teeth off of the gear.

Just some things to consider along with the best ratio for your application.

Randy's Ring & Pinion and Tom's Differentials are great places to get rear end parts. I don't recommend Summit or Jeg's for rear end parts.

 

I thank you for the educational lesson. I guess it probably would be best to just save and cha ge the whole rear out.

 

If you are serious about it, then yes it would.

Then match the gear you use with the rest of the combination. Whats the engine combo? you going street/strip, or wanting drag only?

 

If you plan on daily driving then 3.73 would be the deepest you want to go. With the low first gear of the 700R4, going to 4.10 or deeper creates too much torque multiplication and you'll just spin off the line. Tire spin on the street may look impressive but it won't win races.