Hi,
i have stock 87 caprice with 305 and th700. Since its almost the same most of you have in your F-body, i want to ask you. I would like to upgrade my gear ratio to wake up a bit this boat, now i have stock 7.5 rear end with 2.56 gear ratio, limited slip. I want to keep carrier II series, which can hold up to 3.08 gear ratio and this is my aim. Do i need change anything else beside to correct speedometer? Torque converter can be the same? I have stock tires 225/70R15. Thanks for help, have a good one

 

You can go farther than the 3.08 if you want. There are special thick 3.42, 3.73 and maybe more gears that are made to fit the 2 series in the 7.5 rear ends. This is only true for the 7.5 rear end. You will also need a good installation kit. Might as well change the axle bearings and seals while you are in there.

 

You don't need to change your torque converter. For a 3.08:1 gear, you'll need a 19 tooth drive gear, and a 43 tooth driven gear to correct your speedometer. I suggest you order the thick gears and go on up. For a 3.73:1, you'll need a 15 tooth drive gear and a 41 tooth driven gear. You can go to a 4.10:1 gear, but I'd say that's a bit much for what you seem to be doing. With a 3.73:1, you'll be turning 1750 rpm at 55 mph. Not bad. To feel what this would be like, just drive the 2.56:1 in third gear for a day. Because 3.73:1 times the overdrive ratio is 2.594:1 versus your current 2.563:1 in third. Very similar.

 

Why not just find a 8.5" 3.42 geared axle from a TBI 305/350 9C1 cop car. MUCH STRONGER rear end with a POSI.

 

Only the LT1 cars actually got the 8.5, and not all of those actually got the posi. Even the L99 cars had the 7.625".

 

Thanks to all for suggestions, i think i will stay with 3.08 gearing. Going to 8.5 rear end would be nice, but its hard to find one in Europe, so i will work on what i have now. I have tachometer recently plugged in and the revs are really low with OD, out of peak power

 

most of the 80s cars and trucks were all about low rpm and fuel milage and so most all got horrible axle ratios like this

3.42 was available always but mostly seen in 9C1 and 9C6 packages and most of them got toasted in the hollywood movies like terminator series and so on

78-96 all interchange however

look fo the RPO sticker on the trunk deck lid glued to it for the axle ratio code beginning with G

look for 9c6 or 9c1 and G code that is 3.42

will be what you want

parisienne
delta 88
impala
caprices
and some others


b body wagon ones wont fit the sedans and coupes.. because lower control arms are wider apart from each other on the wagons..

very few taxi and police b bodies survived and didnt get toasted in movies.

most were auctioned off and toasted, or used up in service then crushed

ive owned tens of the caprices and impalas and a few other b bodies i love them all good strong cars and not real heavy and ride so nice comfy