anyone using 4.88 gears

thinking of buying an 8.2 chevelle rearend w/ 4.88 posi anyone have experience w/ these i have a 72 lark w/ 350 4bbl and 350 trans 28' tires(2756015) sounds like it would turn my current 2.56open car into a stoplight screamer what do ya think could i maybe even pull the front tires off the ground a little? anyone using a similiar setup and ya i know i will top out between 85-100 depending on rpm
:3gears: :3gears:

 

I am not going to talk you into or out of getting the gears,but we parted a 71 GS 350 4 speed that had 4.10's in it. The kid who had it told us there were at least 5-6 motors put in the car due to it being over revved with the low gears. They ultimately removed the rear and sat it in his out building and swapped the rear back to a 3.08 set. I have the rear in the garage and maybe someday will use it in my BBB Skylark,but for now the 3.90's will suffice. I predict a fast light to light car with 4.88's but a short lived 350 motor. 3.42's or 3.73's would be a better gear in my opinion..

 

If you are racing 1/8th mile, it would be good. Put a rev limiter on.

 

the more i think about it themore im gonna talk myself out of it too many freeways and highways closeby couldnt do 70 down the road at all probably hold out

 

3.42-3.55`s are enough. I live in a rural area and have to drive on 50-60 mph posted roads all the time. Later,Tony.

 

If you are using the car on the highway...frequently....go with 3.08...anything more and you are wasting gas and your $$$$$

 

I have 3.73 gears in my '57 Special, and I wouldn't even consider taking it down the highway without the overdrive. A buddy of mine had some 4.88s in his '67 Camaro, and that thing ran the 1/8th mile like nothing else. However, he ended up swapping those out for some 3.73s, as he said the 4.88s were just way too much for normal street driving. Personally, I think once you get up to around 4.10s, unless you're running an overdrive, you're building a strip car.

 

It just depends what you're planning to do. I had a 69 Coronet with a 440 and 4.56 gears that was awesome to drive everywhere except the highway.

 

I seem to remember a discussion years ago that indicated a swap to anything 4.10 or higher would just slow you down, can't think like the Chebby guys, they have no torque and have to wind the heck out of the car to get some horsepower, a Buick 455 makes 510 ft lbs @ 2800 rpms!!! You get a good launch from insane torque and most 455 heads are only good to 5500 rpms anyway, so why use up the motor, keep the rpms in the band where it does you the most good, 3.42 3.55 or 3.64 were good enough for the Stage 1's as you throw more and more mods at it, bigger cam, more compression and higher stall torque converter, then go to 3.73 or 3.91.

Sorry, just noticed you have a 350, not sure, but since it is designed similar to the 455 I still have to think mid 3 series rear would be best, for the cost of your rear end swap you could easily add a 150hp shot of nitrous and then you won't hurt mileage when your not hitting the "gas".

 

150shot huh ya that would be fun too just found an 8.5bop out of a 72 cutlass w 2.73 posi would it direct swap w my 8.2bop or is the driveline length different between the 8.2bop and 8.5bop only $200 sound worth it for the fact its posi and i can get more parts for it than the 8.2

 

Buy a set of gears and a posi unit for the 8.5 that your car already has. Monzaz on this board can probably get you a set of used gears and posi unit, and you can pick a ratio that's more closely suited to your intended use. With 4.88s you will need a really tall tire to drive on the street, on a 28" tire with 10% converter slip you'd be running 4500 RPM at 70 MPH. A 30" tire would bring you down to 4200 RPM at 70 MPH with 10% slip. You'd need a lot of motor to use those gears in the quarter, as mentioned earlier it would be a good 1/8th mile gear. If it's your street car, 3.73s on your 28" tire is about as high as I'd recommend.

 

Almost forgot, a governor recalibration will be required with any gear swap to keep your automatic WOT shift points where they need to be as well :TU:

 

Your Cutlass rear with 2.73 and posi carrier just needs another set of gears...go with 3.08 for best all around performance.

When swapping from the 8.2 to the 8.5", you will need to shorten your driveshaft 3/4-7/8"

 

The output shaft RPM changes which should move the shift point a little. The governor is driven off the output shaft of the transmission, so you should see a change as the output shaft turns faster with a higher gear which will lower the shift point. The weights will extend a little earlier, and engine RPM may not be proportionately higher even with the gear difference. When you changed gears, did you change tire height at the same time? 3.42s on a 26" tire are very close to 3.73s with a 28" tire. I dropped about 100 RPM on my shift point changing from a 27" to a 26" tire. The difference is minute but definitely present. Going from a mid 2 series gear to a mid 3 series gear the difference will be more noticeable.

 

thats what i was wanting to know
unfortunately someone swapped out the 8.5 after it broke and now i have an 8.2

 

I ran 4.56's behind a stock 455, and that was way too steep of a gear.

 

anyone know the driveline measurements could i possibly have a shorter 8.5 driveline still bolted to my 8.52 or would it pull out of the trans i need to measure mine and see if i still have the shorter one or if it was swapped also

 

The previous Owner of my '72 GS swapped the 8.5" rear to a Ford 9". That's a 'shorter' rear than 8.5", requiring longer driveshaft (but if it is 'shorter' than 8.2", I do not know).

Anyway; at first he kept the original 8.5" driveshaft, which on the strip caused the slip yoke to strip the number of splines down to zero... :ball: So it does not necessarily pull the yoke out from the trans, but could fail otherwise.

I have not found any data or advice of what the length of driveshaft should be, but actually it would be more important to find and check the dimension, how much does the slip yoke need to extend onto the transmission shaft? That way you can estimate if the shaft is long enough (regardless if it was swapped or not)

But does anybody have the info how much the slip yoke needs to extend on the transmission shaft?