how's a 1991 4.0 Auto geared?

[TwistedCU]

I know it could be one of a few different gear ratios, but can anyone tell me what the most common gear ratio is for a 1991 YJ with an automatic transmission?

If not, if you have that setup could you please just tell me what your stock gears are or were when it was stock?

TIA

 

[Bounty__Hunter]

3.73 is about the most common, with 3.07 and 3.55 possibilities.

 

[yjdave]

I can tell you you probably dont have 373 unless your rpms are around 3500 at 65 w/ little tires. I'm running a tf 999 3spd auto with 4.0 and 36" SS and 3.73 gears and rev at 2700 at 65 mph. What rpms and tires are you using?

 

[joedirt]

I have a friend that had 3.07 in his

 

[TwistedCU]

I have a friend that had 3.07 in his

with an auto? :shock:

The YJ I am referring to currently has 31" tires

 

[yjdave]

with an auto? :shock:

The YJ I am referring to currently has 31" tires

Very possible. in drive the ratio is the same as a 5spd in 4th. Can you check the tag? or spin the wheel and count the yoke?

 

[joedirt]

I'm pretty sure thats what he had I'll double check though

 

[TwistedCU]

Can you check the tag? or spin the wheel and count the yoke?

Nah, the Jeep is an hour from here or I would have counted the revolutions of the DS vs the wheel.

 

[TWDJ]

Just thought I'd throw in my 2 cents. Mine is confirmed at 3.07. I suppose they went real small BECAUSE it was the auto