Best gearing for 31s on a 2.5L auto

Djbtraxxas

New Member
Jan 6, 2019
13
Pennsylvania
I'm picking up a 2.5L auto TJ next weekend for a really good deal. I know that itll suck on highways because it has 31s and lots of steel bumpers and armor which will weigh it down. I've heard that they suck at merging on the highway so what gearing do you run with a 2.5 and auto trans on 31s or 33s? (I dont want to rear everybody saying that I shouldnt get it with that motor/trans. I found a cheap crashed TJ with a 4.0 and I'll swap the engine and trans.)
 

Jerry Bransford

TJ Guru
Supporting Member
Nov 9, 2015
9,941
Escondido California
For the effort and trouble it'd be to swap in that 4.0, even though you said you don't want to hear this, I'd wait to find a good deal with one with the 4.0L already in it. Not to mention you'd also have to get inside the transfer case to swap in a different (larger diameter) input shaft or swap the 231 tcase too.
 
Reactions: Chris

Chris

Administrator
Staff Member
Sep 28, 2015
35,326
Salem, Oregon
The other issue is that the hearing ratio will change when you swap in the 4.0 and it’s transmission. So I wouldn’t gear for the 2.5 if you just plan on ripping it out.
 
OP
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Djbtraxxas

New Member
Jan 6, 2019
13
Pennsylvania
For the effort and trouble it'd be to swap in that 4.0, even though you said you don't want to hear this, I'd wait to find a good deal with one with the 4.0L already in it. Not to mention you'd also have to get inside the transfer case to swap in a different (larger diameter) input shaft or swap the 231 tcase too.
I'm honestly looking for a big project to do next winter so I might do it just for the hell of it. If I can find all the LS swap pieces for cheap I would rather do that
 
Reactions: Jerry Bransford