86 Cutlass Rearend

[zildjian4life218]

Okay i have an 86 Cutlass Supreme with a small block chevy in it. It has a 10 bolt rear end in it. Not sure if its a 7.5" or 7.625"; can someone help me identify what i have. Also I am dropping in a 350 that will be putting out around 350 hp and 400 ft/lbs. I want to know if the rear end will hold up. A lot of people said the 7.5" are very brittle and will come apart with little over 300hp. thanks in advance for the help.

 

[pontiacman469]

Your buttocks is a 7.5 What you have for gears is hard to tell probably in the 2s... 2.14,2.41 Shouldn't be a issue with a mild 350.If your pockets are deep an 8.5 from a grand national is good isurance.

 

[foxtrot]

R u a drummer?

That rear will be fine as long as your not beating that crap out of it for 40k miles per year. I have a 7.5 rear behind 350hp that is holding up fine...

 

[DRIVEN]

You probably wont hurt it if you aren't flogging it mercilessly - especially with a "highway" ratio. Ironically, the lower the ratio is, the more fragile the gear set. Have you ever seen the size of a pinion gear in a set of 5.88s? Tiny! Less teeth = less gear contact = less strength.

 

[zildjian4life218]

Yes i am a drummer. Been playing for about 8 years or so. Haven't really had the time lately. I plan on changing the gears to 3.42:1. Is that a good ratio to stick with for a TH-350? I want to go 3.73 but without an overdrive trans i think that would be overkill.....any suggestions? Thanks

 

[Blake442]

Without overdrive 3.73's are a little tough on the highway.

3.42 would be good but 3.23 might be even better.

 

[zildjian4life218]

I couldn't decide between 3.23 or 3.42 but the car will see more city than highway miles

 

[DRIVEN]

If you do a Google search for "RPM calculator" several sites will pop up. These will allow you to enter the specifics of your combination to decide things like this. By using my current specs (TH200 / 2.29 ratio) I found that I could use a 3.42 ratio in conjunction with the TH200-4r I will be installing and have the same cruise RPM (because of the overdrive) but get the benefit of a much deeper low gear which means much quicker out of the hole. Look up one of those calculators and play with it. It's a fun way to waste time.

 

[zildjian4life218]

Thank you very much for the suggestion on the rpm calculator. I will definately play around with it.

 

[DRIVEN]

Let us know what you decide on and how it works out.