Rob Edwards

The proper work-around would be to pull the transmission and replace whatever ring and pinion that 's in it with the 'correct' 2.20 R&P. But that's kind of a PITA, unless you're planning on doing a lot of highway cruising with it. I'd leave well enough alone, especially if you do have LSD.

Since the factory options list is a little suspect, the easiest way to 100% prove that you have LSD is to spend $15 on an a USB endoscope


http://www.ebay.com/itm/2m-5m-7m-10m...item3a83eeb208

and then open the upper plug on the rear of the diff, and take a snapshot of what's inside.

I tend to think that the car was built as a 5-speed, unless someone did a _Very_ good auto to 5-speed conversion. Maybe there was a transmission failure during some PO's tenure and they had it rebuilt with a shorter R&P and LSD?

CoachTom

Engine SN: M28/43 81G 006

What am I supposed to see or photograph on the borescope? I know this has a LSD so doesn't that assembly block the view of the pinion?

I do believe this was a factory install (confirmed M28/43) as i gave the whole assembly a hard look tonight to see what it was going to take to remove/repair and all underneath is "tight", relatively all worn or used alike. It couldn't be anything else, could it? Why would the R&P be so short? I live in Alabama and yes, highway miles are all we drive (geographical oddity, two hours from every where)...

CoachTom

Seems PO had changed the transaxle of this car to a 2.72 final drive and added a LSD. The original factory transmission had a 2.20 final drive without an LSD it appears...

I guess the esteemed participants on this list could tell me why this R&P ratio is something someone would drop some significant coin upon to change to.

Now to find a 2.20 to swap back into the transaxle as I usually drive long highway miles down here in Alabama...

Thanks to all for the help!

TMcD

Bilal928S4

Would incorrect wheel/tire size affect the rpm vs speed ratio?

Kevin in Atlanta

PM sent.

mark kibort

no, not at all. they are tied together regardless of if you were running on the rotors.

mark kibort

we have spent hours on this list talking about it. the bottomline is a rounding error in performance, as it changest its sweet spot to acceleration rates at different speed ranges. However, some like that "feel" of greater acceleration in the slower speed ranges, even though overall there might not be any change , and sometimes even less depending on the speed ranges you drive at.

a 2:2 goes:
0-55 1st
55 to 80 2nd
80 to 115 3rd
115 to 155 4th
155 to 225 5th. to redline.

so, with a 2.72, 5th is the greatest change because it is direct, but all the other gear ratios are changed in the gear box as well, so the actual difference is only about 10% per gear numerically higher ratios.

So, if you like 80 to 115mph acceleration , the 2.2 is best.
if you like 60 to 90mph, the 2.73 is best. (as a rough example)

gearing doesnt create hp, it only optimizes what you have for a given speed range.

James Bailey

Depends on if the lay shaft ratio was or was not changed when the ring and pinion was changed....all gears but 5th the power transfers by the lay shaft before jumping back to the pinion.....and USA vs Euro have different gear ratios for those lay shaft gears.
Not as simple as it might seem.
And one would need to drive many thousands of miles to ever begin to "save" enough money on gasoline to offset the costs of rebuilding a transaxle which you MUST do to change the ring and pinion on a 5 speed !
Get some 18 inch rims with 295x35x18 tires and the change in tire circumference effectively changes the final drive MPH per RPM