Final gear ratio?

[Guest wally888]

What are possibilities for 88, 89, 90 and 91.

Are all 91's .333?

All 90's ??

89's??

88's??

Appears recent post about this-Performance Data-is in error?

Says 90 and 91 both .333?

[reattadudes]

Wally,

all my dealer books show 1988-1990 models had a 2.97 ratio, and the 1991s were the only ones with the 3.33 ratio.

Mike

[padgett]

Keeep in mind that many transmissions have now been replaced and might not have the original ratio however 2.84 (Riviera), 2.97, and 3.33 (most 2.8 engines) seem to have been the most common.

[Guest wally888]

My 91 shows 1600 RPM at 50mph ( Collant temp 180*,Cruising w/ overdrive engaged).

Shouldn't I see something less (RPM's) under the same conditions on the 90?

[2seater]

I don't know about your '90 but mine is turning less than 1500 rpm @ 50. Tire size wouldn't matter as the VSS signal and engine rpm are linked before the actual rubber meets the road. As for the 3.33 gear ratio vs the 2.97 in the earlier cars: the '91 used a slightly larger diameter tire as standard so to compare the two, the '91 actually performs like a 3.25 ratio would in an earlier car, with smaller tires. Small potatoes, but it is not quite a direct relationship.

[Guest wally888]

A few years ago I owned an 89 and 91 coupe. RPM differences were 3-400 @ 65 mph. 91 being the highest.

I searched for the exact difference (posted here at that time but can't find post). Was questioning gas mileage as the 91 was several mpg less than 89.

The current 90 is parked waiting for ordered tires and shocks and 50 mph is about as fast as I care to drive it right now. Will persue comparision after she is ready for the Interstate.

I printed out shift intervals for the 90 from FSM but as yet haven't identified the exact tranny in the 90, which chart to use. I found the sticker in the trunk, still confused and can't find labels on tranny.