GEARING for 92 YJ - what say you?

jaysyro

jaysyro

Member
Joined
Apr 21, 2021
Messages
33
Location
New York
Hey everyone - Here to ask a common gearing question to which I have never received a clear answer on …

I have a 92 YJ geared at 3.55. Automatic transmission. 3 gears. 4 inch lift. 33x12.5 tires.

I live in NY and this is my one and only car. I drive through NYC nearly everyday. A lot of stop and go traffic, potholes, bad roads, etc. I also take 1-3 hour trips rather frequently where I’m spending time on the highway going 70, 75 MPH. Currently I can hit 75/80 pretty smoothly but I struggle on inclines and definitely struggle with quick acceleration on city streets or even just getting my speed up on any road. Every now and then I am also driving to areas with steep inclines and occasional dirt and muddy roads where my current setup really lags and struggles. I’m also on stock Dana 30 (F) and 35 (R) axels.

Contemplating 4.10s or 4.56s and Connor find a good answer. Thoughts?!

A10ACEB4-E86D-4B54-8532-65E880A4D036.jpeg
 
I just went with 4.88s for my 2.5, what a marked improvement over the stock 4.10s!
70mph, No problem.
With an auto tranny, that may be more than you need, but given your tire size maybe not...
I would have gone with 5.13s, but I have a 4 speed truck box conversion in the future and I'll be losing 5th gear.
 
4.10 for the 4.0 auto, that will keep good highway performance, good around town, without too crazy high highway rpm. It’ll be around 3300 at 75. If you go to 4.56 that becomes 3600. And any lower like 4.88 - 5.13 you start to hit 4000s on the highway.

I did 4.88 for 33’s but I have the AX15 5-speed manual. It will do about 3000 at 75 and should be great, but I have all those gears low down helping me get rolling. The auto needs to sacrifice higher highway rpm for more grunt down low since it only has 3 speeds.
 
  • Like
Reactions: jeepjoe43
To add, the auto will never perform in town like a manual simply because it doesn’t have that many gears. Even if you geared it to 4.88 for 33’s like me, it wouldn’t perform as well because of the lack of gears, although the torque converter helps with that. Of course, you wouldn’t want 4.88 because of the highway top end issue. But you should be quite happy with 4.10 & 33’s.

The auto is a great trans in general though, not trying to talk down on it. It’s just better at different things than the manuals are. If I were building a trail rig I would get an early TJ or YJ with the auto.
 
jeepjoe43 said:
4.27s might be a good compromise,
A buddy of mine had them in a CJ7 with a 304 auto, and it ran like champ.
But I'm a lower the better kind of guy.
Click to expand...
I think 4.27s are D44 only and not available for D30 IIRC.

Edit: weird looks like 4.27 is available. I swear that is newer.

edit 2: looks like they are only for the non high pinion 30, so not for YJ. And I believe they work on the CJ 30 but not the TJ LP30 because I think they have different pinion lengths.
 
jeepjoe43 said:
You could be right, Macho.
Not sure if 4.27s are available for the reverse rotation D30.
Being a CJ7, his had the std rotation D30 and Corporate 20.
Click to expand...
Yeah I believe they are available for the CJ 30 (long pinion), the AMC 20, and Dana 44. Sadly not YJ 30, TJ 30 (short pinion), or D35. That is from my limited digging anyways. But there were always reasons on the forums why YJ and TJs don’t run them. I believe the rubi can though since it’s LP 44 F&R. But those all come with 4.10 already so nobody is really making that jump, they’re all going to 5.13+ with their 35’s, manuals, and their shitty 4 speed auto with a ridiculous OD.
 
  • Like
Reactions: jeepjoe43
machoheadgames said:
Yeah I believe they are available for the CJ 30 (long pinion), the AMC 20, and Dana 44. Sadly not YJ 30, TJ 30 (short pinion), or D35. That is from my limited digging anyways. But there were always reasons on the forums why YJ and TJs don’t run them. I believe the rubi can though since it’s LP 44 F&R. But those all come with 4.10 already so nobody is really making that jump, they’re all going to 5.13+ with their 35’s, manuals, and their shitty 4 speed auto with a ridiculous OD.
Click to expand...
I did some limited digging too, and I found squat for the YJ.
 
machoheadgames said:
4.10 for the 4.0 auto, that will keep good highway performance, good around town, without too crazy high highway rpm. It’ll be around 3300 at 75. If you go to 4.56 that becomes 3600. And any lower like 4.88 - 5.13 you start to hit 4000s on the highway.

I did 4.88 for 33’s but I have the AX15 5-speed manual. It will do about 3000 at 75 and should be great, but I have all those gears low down helping me get rolling. The auto needs to sacrifice higher highway rpm for more grunt down low since it only has 3 speeds.
Click to expand...
Thanks for this! If I was to get 4.56s, how much truly louder is it on the highway compared to 4.11s? If I’m at 75 on the highway is my car going to be significantly louder with the 300 extra RPMs?
 
  • Like
Reactions: jeepjoe43
Depending on gear sway costs you might consider finding a pair of axles from a wrecked 4 cyl YJ as they will have 4.10 gears from the factory. BTW, those tires sure look big for 33's. Must be the picture.
 
jaysyro said:
Thanks for this! If I was to get 4.56s, how much truly louder is it on the highway compared to 4.11s? If I’m at 75 on the highway is my car going to be significantly louder with the 300 extra RPMs?
Click to expand...
Louder? I dunno, probably not much. The fan spins a good bit more at 3600 than 3300. I’d probably slow down if I went with 4.56. 3000-3100 at 65 isn’t too crazy loud which is what 4.56/33 would produce. But me personally would just go 4.10 & 33’s.

I never felt 75 was too fast, but much more than that is. Mine was always stable when I was daily driving it, drove like any other vehicle to me other than the rough YJ ride and loud YJ noise.
 
  • Like
Reactions: jaysyro
Top Bottom