wondering everyones opinion on replacing my 3.91 gears to 2,93 gears that i have under the bench. my car has a fairly stout 455 that runs 12,20 at 112mph.I dont drag it anymore and want to cruise with it.have a turbo 400 with a kenne bell switch pitch,I dont really want to spend the money on a gear vendors overdrive. any thoughts??
Your car should have enough torque that you wont find it a problem, and the SP makes it even easier to take..
I ran a 2.93 in my gs455 convertible, small cam, headers, everything else stock. The car ran 14.0 in Bristol TN. and it had plenty down low for me.
Do it. If you had a high stall convertor, then I'd be concerned. But I'm assuming your low stall in the switch pitch won't have you slipping on the freeway. I had a 2.56 geared Skylark that was "incomplete." I drove it to the track to race, but because of the stall and gears, I left it in 2nd on the highway to keep it from slipping and heating up the trans. That's not a problem for you if your low stall is under 2000. If you were debating between something like 3.91 and 3.55, I'd probably suggest getting a taller tire to mitigate the difference. But that swap is reasonable, and you've got the torque to pull the low rpm with that ratio.
Swap it, the Switch Pitch will absolutely love it. You'll get more stall out of the converter in Hi, and the Lo stall will be fine.
While 2.93/3.08 was the stock ratio for a non Stage big block car, I personally would miss the grunt from the 3.9 gear.. I did this years ago, but in reverse.. GS has the stock 2.93's went to a 4.10 gear, and loved it.. but I was a teenager, and rarely ever drove it on the highway. I think the Standard Stage 1 AC gear is the best compromise.. 3.42.. If your doing a lot of highway driving, and you have a complete drum to drum 2.93 rear to swap in, then go for it.. you can always switch back.. but if your talking about just changing gears, and have a 8.5" rear, I would buy a set of 3.42's. If you have the earlier rear end, that might not be an option, been a while since I brushed up on what is or is not available for the late 60's 10 bolt Buick rears. Anyway, good luck JW
Yah watch out for the carrier you will need the correct carrier break to do that swap. 68-70 is 2.56 series 1 2.73- 2.93 series 2 3.23 3.42 series 3 and 3.64 - 5.00 is series 4 In the avatar it looks like a 68 69 era car... Jim JD RAce
So unless you tell us what rear you have under the vehicle you are just beating a dead horse... 8.25 68-70 rear you can not even get parts very easy for. IF you need a posi I have a compatible retro fit unit for 2.73 and 2.93 ratio gears in the 68 - 70 rear. 3.42 gear you will either need to WAIT for fabcraft to build in a decade or 2 or find a USED gear set and you will still need a different carrier again. So I would ID what you have first ...then you will know what direction you can and want to go in. Jim JD race
Its an 8,2 rear end i did the 2,93 to the 3,91s twenty five years ago in the same rear end, i want to do the reverse and put in the 2,93 gears. the carrier was for the 2,93,when i put in the 3,91s I used a spacer on the carrier and longer bolts made by a machine shop.I never ran the 2.93 gears in my car,it was just the gears that were in the rear end when i swapped it out.What the chance of getting a new crush sleeve for the pinion?
I have retro fit crush sleeves if you need. Just use the start conversation on the avatar. So now we have that all cleared up. :0 Then there should be no issues with the swap. How many miles you think you have on the stock posi unit? Might want to open it up and see if the cones are close to bottoming out. EVERY left and right turn makes the posi cones wear. Jim
I ran 2.56 for years in my SunCoupe. Didn't have a trailer so it got me there and still ran high 12s. Went 12.66 at Cecil one time in 2nd gear at 109 with it's tongue hanging out! I put the 3.90 gears back in for my son to have a little more fun and low 12s. Still have the 2500 conv that I put in for the 2.56 gears. Had a 3800 conv that would not work with the 2.56. You could be going up a hill at 2500 in 2nd and shift to 3rd and little if any rpm change! Might put that back in but the motor has been in car since 1988 and a stock unrebuilt Buick-built 70 shortblock. Maybe I should give it a break.....
Humm. 3.90 should have been worth more than a 1/2 sec ??? I did a swap from 3.55 to 3.73 and gained a 1/2 sec. of coarse I had to have slicks or all was a moot point. 2000 stall 700r4 1971 Monte SS 454 (4000# SCALED) POWER EVERYTHING- SEAT (ONLY ONE LOL)WINDOWS, LOCKS, TRUNK NOT A RACE CAR FULL INTERIOR. 272 crane hydralic cam performer manifold holley 750 DP 781 emission heads 120cc ports 10 -1 compression engine has 200cc pop ups (iron heads 2.06 / 1.72 ) learned a lesson on compression YEARS AGO. that was not fun on the street....lol 12.80 WITH 3.55 12.35 WITH 3.73 not trying to knock anything just saying maybe something is not right unless your doing it with out slicks and the 60 foot is suffering...then I get it.
