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Following my conversion to a 6 speed BMW manual gearbox I am trying to get the diff ratios a little taller - can we still get high 2's? would love to drop the rpms in 6th down a good chunk - i think i have 3.08 at the moment but looking for the lowest available ratios i think!
How low of RPM do you want in 6th gear? What speeds are you running in six gear, typically? Do you have a fairly stock engine or a sizeable camshaft? Just curious what is the sixth gear ratio and that BMW transmission?
right thank you all - if 3.08 is the lowest (which I already have) then its probably not worth finding any gears. I did contemplate using a BMW diff but I know the vettes use the diff as part of the suspension geometry - not sure how the BMW diff would like that weight compressing it if i made one fit.
cruising at 70mph is still only 2300 though so its liveable!
Following my conversion to a 6 speed BMW manual gearbox I am trying to get the diff ratios a little taller - can we still get high 2's? would love to drop the rpms in 6th down a good chunk - i think i have 3.08 at the moment but looking for the lowest available ratios i think!
So with an overdrive 6 speed manual (IF it has an OD gear) I would think you would want something lower like a 3.55 or 3.73 gears... I just went from a 3.08 to a 3.55 because im installing a 4 speed auto to replace the 3 speed th400. More gears typically mean a lower first gear.
If the bmw unit does have an overdrive you will barely be able to use it with 3.08 gear and only at high speeds... a 2.xx gear would be even more of a mismatch I would think. and you would be lugging the engine likely causing bearing damage.
273 was ratio offered by both GM and Tom's. It has been discontinued and I don't believe there are any current new offerings, but you may still find them online from time to time. Keep in mind that the gears, axles, posi are all specific to corvette so they won't interchange with other models.
It's easy to figure out your differential ratio. Jack your rear tires off the ground and mark your your drive line. Just count the rotations of the drive line to the tires. Generally 79 C3 vettes had 3.55 gearing unless they were ordered with something different.
Wooforduk, could you share with us how you performed your BMW 6 speed conversion? The BMW transmissions that I am familiar with have integral bellhousings.
What are your 6 speed gear ratios? How much TQ can the tranny handle? Years ago I liked the idea of the richmand non OD 5 speed. but the problem was lack of TQ handling. I installed the TKO 600
Yes, very impressive. Did you do all the measuring, designing, programming yourself? May I ask how much time and money machining something like this takes?
Diff Ratios
