I have an 82 Crossfire TransAM, 5.0 litre with 3-speed auto box and 225/60 R15 tyres :
in the past, someone has changed the diff, as when sitting at 4000 rpm, you are sitting at 80mph in third. It's a bit embarrassing with all these euro-boxes blasting past you on the motorway at 90 mph or so.....

I gather the diff has been changed to that of a 5 speed manual or 4 speed auto, being too low-geared (?) for the 3-speed auto.

Anyway, what's the best ratio - 2.73, 2.93 or 3.23 : 1 ? Will the 2.73 be hellish-slow on acceleration ? Will the 3.23 be of little or no improvement ?

My speedo over-reads like crazy because of this, the 4000 rpm at 80 mph reading being obtained trying to keep up with my uncle's car on the motorway , sitting behind him at 30mph, 40 mph , 50 , 70 and 80 mph respectively while I noted my readings on the rev-counter.

Any advice would be much appreciated.

Many thanks

 

When I had 2.73's in my car with the 5.0L it ran high 15 low 16 quarter mile times, but it would run 85 mph at 3000 RPM in 3rd gear. I would think that the 3.23's would give the best of both worlds.

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'87 Bird 350 .060 over 700R4 + Lots more

 

many thanks for that - reckon I'll go for the 273's - I like the sound of a (much) more relaxed cruising speed, and I suppose better fuel economy (crucial over here !)

Many thanks again