newb transmission axle ratio question

[90 3800 lesabre]

so my 90 lesabre once again needs a new transmission.. YAY... well it needs a new transmission, i rebuilt mine 3 years ago or so, but i was woundering about the diffrence in the axle ratio. i know the bigger the number is the harder it take the engine to turn the gear to turn the axle so on so forth. but on this web site it is list differntlythen what im use to seeing, like 2:1(example) axle ratio, but on this site it has two tranys that would fit, one tranys axle ratios listed as 2.84 and the sec trannys axle ratio is listed as 2.97. so in summery what is the diffrence between the way u write the axle ratio, and is there a huge diffrence between the two.

[Blue Bowtie]

A lower (numerical) final drive ratio would allow for higher vehicle speed at a lower engine RPM. A lower numerical ratio can also allow for better fuel mileage, but will cause the engine to work harder to get the vehicle moving (poorer acceleration).

That said, I believe the final drive ratio of most of the older transaxles was around 4.10:1. Coupled with the overdrive ratio of 0.70, that would net a ratio of around 2.87:1.

The difference in the two final drive ratios you have listed would mean that at 60 MPH road speed, the engine would be spinning about 100 RPM faster with the 2.97 than with the 2.84. It's not that significant a difference.

[HotZ28]

Originally Posted by Blue Bowtie

That said, I believe the final drive ratio of most of the older transaxles was around 4.10:1. Coupled with the overdrive ratio of 0.70, that would net a ratio of around 2.87:1.

Actually, the 2.84 & 2.97 ratios are two of the “final drive ratios” in the 4T60 in 3rd gear. (Third gear is 1:1) Forth gear is overdrive @ .70, so therefore, if you have a 2.84 final drive ratio, the overdrive ratio (4th gear) would be 1.988. (2.84 X .70). The 2.97 would yield a final drive ratio of 2.079 in overdrive (4th gear).

If you did actually have a 4.10 final axle ratio, with a .70 overdrive, you would have a final overdrive ratio of 2.87:1 (4.10 x 0.70 = 2.87) in 4th gear (overdrive).

Tire diameter will also have an effect on a vehicle's final drive ratio. As tire diameter changes, so will engine rpm at a given speed.

[Blue Bowtie]

No wonder my daughter's LeSabre cruises down the road at 65 MPH at about 1,600 RPM.

[90 3800 lesabre]

O ok i get it well thank you guys that helped alot thanks again