85-OD/90-OD ?

[ON 7TH]

My 85 will cruise at 60mph at around 1500/1600 rpm's
My 90 at 60MPH is around 2300/2500 rpm's
Can some one explain the difference.Both cars are stock automatics.Thanks!

 

[ZumZum]

My 85 will cruise at 60mph at around 1500/1600 rpm's
My 90 at 60MPH is around 2300/2500 rpm's
Can some one explain the difference.Both cars are stock automatics.Thanks!

Well, the short answer is they have different gears in the differential.
The 85 must have the 2:73 ratio. The 90 more then likely has the optional 3:33 ratio.

 

[Tuna]

That's my guess also. Check the RPO listing for G92 on the 90 for the 'performance axle' option. Additionally, here are the RPO's for the different axle ratios from the Tech Center/Model Center here:

G44 - Rear axle 3.07 ratio
G87 - Ring gear 8.50 inch
G92 - Rear axle performance ratio
GH0 - Rear axle 3.54 ratio
GM1 - Rear axle 2.59 ratio
GM3 - Rear axle 3.45 ratio
GT7 - Rear axle 3.33 ratio
GU2 - Rear axle 2.73 ratio
GW4 - Rear axle 3.31 ratio

 

[G Winter]

Not sure if my tach is right but my 90 has the 6 speed and the GT7 3.33 gears. It runs around 1650 or 1700 at 60 mph. I would have to look and see how the overdrive compares in ratio to the auto, but this gives you something too work with.

Glenn

 

[ON 7TH]

Thanks guys! Ill check the rpo code for the rear ratio.