Author Topic: diff ratio, not happy (Read 9286 times)

87droptop · « **on:** March 04, 2011, 12:17:15 PM »

hi everyone, took my car out for a test run for the first time yesterday, and i know the diff ratio is 4.11, it was not much fun to drive, revvs too high at 60 kmh.....and obviously runs a bit hotter since it produces more heat at higher revs for the same speed, and.. fuel ( that dont matter much), so, any one know what standard ratios these have , 1968, was 350, now 383, and any suggestions to what is good for it??? i was thinking anything around 3.2 or 3.3, if it exists..
thank u all again

MADLT1 · « **Reply #1 on:** March 04, 2011, 04:23:58 PM »

mine is a 3.36 ratio,it a good all rounder,mine is a 383 aswell with 4 speed,revs high on the freeway but good for every day use,other than that if your not worried about originallity what a dougnash 5 speed behind it?

sirfixalot · « **Reply #2 on:** March 04, 2011, 08:38:10 PM »

Is it manual or auto? There is 3.08 3.36 3.55 ratios, gear set is about $400 to buy then you have to R & R diff & also cost to set up gears in diff, then you do wheel bearing, suspension bushes, uni joints, paint everything while your in there.

87droptop · « **Reply #3 on:** March 04, 2011, 10:35:39 PM »

yeah, i've done all that already, it took 2 years... just went thru the whole car, i've never had a 4.11, so i thought i would wait and c how it is gonna drive. $400 for diff gears in the states or here?? if i were 2 change gearbox, maybe to a 5 or 6 speed if possible, then would keep this diff.. how many revs does yours sit on while doing 100 or 110 km/h mate??

87droptop · « **Reply #4 on:** March 04, 2011, 10:57:07 PM »

and, yes it is manual.

gtc · « **Reply #5 on:** March 05, 2011, 12:26:43 AM »

Have you made allowance for those big wheels in your speedo gearing?

If you want to play around with various diff ratios, put your data into this. Like most of these calculators it uses mph, but your '68 would have a mph speedo unless you have changed it. These calculators are not super accurate, but they are close enough to be useful for diff comparisons at highway speeds.

http://www.f-body.org/gears/

I'm guessing you have a Muncie M20 wide ratio box (most commonly installed), in which case the ratios are:

1st 2.52
2nd 1.88
3rd 1.46
4th 1.00

87droptop · « **Reply #6 on:** March 05, 2011, 05:24:45 AM »

no, didnt allow for the wheels, even though they r big, didnt make much difference to the final ratio, not drivable around like this... i think it is a muncie gearbox mate,so the final gear is 1:1 u r saying, then a 3.08 or 3.36 might do for diff gears...

87droptop · « **Reply #7 on:** March 05, 2011, 05:36:44 AM »

this calculator is great mate, thanks, i thimk 3.08 is gonna be it...

sirfixalot · « **Reply #8 on:** March 05, 2011, 08:24:48 PM »

I have a set of 3.55 gears that have been lapped by diff technics & are ready to go into diff you can have for $200

87droptop · « **Reply #9 on:** March 06, 2011, 07:36:16 AM »

3.55 is a bit too high mate, thanks 4 that anyway..

RHD.68.l89 · « **Reply #10 on:** March 06, 2011, 09:37:15 AM »

Sorry but I think you are going to need a new diff centre. The 4 series carrier is different to the 3 series. The offset is bigger to get more teeth in.

87droptop · « **Reply #11 on:** March 06, 2011, 06:35:36 PM »

now u lost me, aren't the diff casings the same but the the pinion and ring change????

sirfixalot · « **Reply #12 on:** March 06, 2011, 07:03:11 PM »

Yeh forgot about that with 4.11 gears you also have to change the hemisphere also to run 3.55,3.36 gears

RHD.68.l89 · « **Reply #13 on:** March 06, 2011, 11:18:30 PM »

Case is the same, centre carrier is slightly different