i have a small block running my 72 impala, an i still have oem 10 bolt 8.5, my car will be on 22" budnikz this fall, an im tryin to find a gear/ diff. set up for it, right now im looking into a eaton 28 spline posi unit an a set of 3.73 gears, an i wanted to know if anyone else has been through this conversion, are 3.73 ok for a big car? or should i consider 4.10's? also im using a 350th with a long tail , thinking about swapping for a 400th since im on my 3rd 350th an flywheel..... my 2500 stall seems to help a little.... any tips?

Before I pulled the 305HO out of my Caprice (9C1) I was running a 3.73 Eaton Posi in my corporate 8.5" 10 bolt with the stock 200R4. Great acceleration (actually spun both rear 235R70x15 tires leaving lights) with the 200R4 I was well above my torque converter stall point in OD. I was actually running 14.84 @92mph with this tank and a few minor modifications.

I have since swapped out for a built 700R4 with a 3200 RPM stall converter behind my new 500+hp 406 I've dropped in place of the tirred old cop car 305. The motor is actually now running below the torque converter's flash point in OD; but the lock up clutch is still holding so it appears to be ok. I may have to go to a steeper gear if the engine's torque is too much of a strain, only time will tell. I haven't tried it at the strip yet but I know it will put down a freinds car running 12.50's now, with little effort (I'm hoping for low 11's)


Big Dave

now c i was told that an od tranny would need low gears like at least 3.55, 3.73, but 4.10/4.11 would be better, i have a built 350th, 2500 tci stall, stock 3 series gears, 10 bolt, sometimes it feels like both r spinnin, but when i look at it myself only pass. side, my acceleration is better than most think it should be for its size, but that was before the motor build, i've changed all internals, an exhaust, est. 355/365hp. i guess i just want to feel more torque or better take offs, wut year is your 9c1? my 72 weighs close to 4500.......an its a 4 dr....

4300 pounds; '89 4Dr Sdn. My other car ('85 Impala 4Dr Sdn) has a 582 in it. Built it with all 9C1 parts, from junk yard donors. It has l-o-t-s of torque, but doesn't qualify as small.