87droptop

Rear gear topics come up quite often. Here is my experience. On my '87, I went from a 2.59 to a 3.55. Had to do the tranny gear and sending unit swap for everything to be right. It's a totally different car. Very nasty from a dead stop and the 2nd gear shift will kick the car sideways! At 70 mph, the car is more lazy than before. I lost about 2 mpg. Was it worth it? For me, absolutely. I do most of my cruising in town, so it holds it's own from stoplight to stoplight. I doubt if it is quicker thru the 1/4 (at least the last 500 ft.), I'll have to try it.

383vett

It'll be quicker in the quarter.

87droptop

From 14.2 @ 99 mph to high 13's perhaps? (with sticky tires).

383vett

With sticky tires and gears, at least 3 tenths if not more.

ghlkal

Thanks for sharing this.

What RPM at 70mph with the 3.55?

87droptop

I've got it in storage right now. I need to drive it again to give you an actual #. But if my memory serves me correctly, I think it was turning somewhere between 2400-2600 rpm at 70 mph.

Rodney_Gold

I did the same to my 86 , wonderful change and best bang for the buck seat of the pants wise.
Going from the 2.59 to the 3.55 is like losing overdrive for top gear , you can just leave you car in D and check what RPM you getting , that's what you will get with the swap.
IMO it was an idiotic decision to use a 2.6 ratio in a performance car in the first place.
Initially I got much worse mpg , I was enjoying nailing it too much , but in "calm" driving , it is maybe 10% worse. However I don't see the point of buying a vette if you terribly concerned about MPG.