How can I find out what trans I have and whether or not my axle is Limited Slip? I am pretty sure I 4.10 gears, or atleast that is what the rear end says on it. If it help I have a 99 4.0 4x4 ext. cab

Get the axle code from your door sticker and reference it here:
Code Description # Capacity Ratio
42 3.45
44 3.73
47 4.10
72 Regular 2200lbs 3.08
74 Regular 2200lbs 3.45
82 Regular 2700lbs 3.08
84 Regular 2700lbs 3.45
85 Regular 2750lbs 3.55
86 Regular 2700lbs 3.73
87 Regular 2700lbs 4.10
91 3.27
92 3.08
95 3.55
96 Regular 3200lbs 3.73
F4 Limited Slip 2700lbs 3.45
F5 Limited Slip 2750lbs 3.55
F6 Limited Slip 2700lbs 3.73
F7 Limited Slip 2700lbs 4.10
K6 Limited Slip 3200lbs 4.10
D2 3.45
D4 3.73
D7 4.10
R5 3.55
R6 3.73

You can also crawl under your truck and look at the tag on the diff cover. The ratio will be mixed in those numbers somewhere. If it's a limited slip there would be ls between the ratio numbers (I think) like....4ls10 (?) or something like that.

There would be an L between the ratio, example 3L73, hehe. Jarret almost got it all perfect :) Since you have a 4.0 I can already tell you that you have an 8.8 rear axle and most likely the traction lock, which is the 3L73 gear ratio. You coudl have a 4L10 though.

Originally posted by ChrisC97
There would be an L between the ratio, example 3L73, hehe. Jarret almost got it all perfect :) Since you have a 4.0 I can already tell you that you have an 8.8 rear axle and most likely the traction lock, which is the 3L73 gear ratio. You coudl have a 4L10 though.


Thanks for the correction. :)

Jarrett, you can add another to your list.

R7 Limited Slip 3200 lbs 4.10

It's on the 01's. Looks like the same description as the K6.

coll thanx guys i always wondered what rear i had, just never took the time to look it up. I have a regular 4.10. . Not LS, but owell i keep it on the pavement usually. . . . :drunk:

Good to know, I finally took the time to check my door and it appears to be 86 (3.73 standard) I have 225/75/15's on a stock 2.3l what advantages/disadvantages would the 4.10 bring me and how about limited slip???

The advantages of the 4.10 gears would be.... Better low end power,and more fun to drive. The disadvantages would have to be gas milage The 4.10 gear seem to suck the fuel needle in the down position more often. The limited slip would give you better traction from a stand still, less wheel spin and the L/S gives that great 2 wheeled burnout all of us like so much.:beer:

how bad would 4 10 hurt your top end speed?:afro:

Thanks for the help guys, do you also know the codes for the 4 speed auto and the 5 speed auto. I am not sure which trans. I have.

I'm not sure which is the trans code, but under "TR" on the door sticker mine has a D, and it's a 5 speed auto. I may be mistaken, but I think 99's were the first year they offered the 5 speed auto. I considered getting it on my 99.

This is what my door says, under the A is K, under the R is 97, and under the TR is D. Does that mean I have 4.10's and a 5 spd auto? I know for sure that the rear end says 4.10 on it. Thanks for all of the help.

Sounds like you have the same code as mine, and I know it's a five speed auto. You should be able to tell by the shifting, It will take off, shift 4 additional times, then lock the converter which feels like another shift.