• Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.

What Gear Ratio to run

What Gear Ratio to run
W

wooderson64

Jeeper
Posts
20
Thanks
0
Location
Nashville
Vehicle(s)
79 cj7
Ive got a 79 CJ7 , 360 with 3speed, spring over and 35's. Im wondering what the best gear ratio would be to use in the differentials. I only drive the jeep to the trail and do general 4wheeling, a little of everything on the trails. So driving to and from the trail with general trail riding. Thank you for any advice!
 
How much highway and at what speeds?

I also have a 360 & 35s and the T-18 4 speed is like a 3 speed on the street. I run 4.10s but even with the granny gear, I added a 2.46 low range to Transfer Case to help out on the tail. If you are going to keep the 3 speed, then I would look at either 4.56s or 4.88s. 4.56s should put you around 2700-2800 rpm @ 60 mph and 4.88 would be around 9
2900-3000 rpm. If you have the AMC20 then I think 4.88 is as low as you can go.
And if you plan on any serious off roading, then I would also plan on going with a 3.15 low range to help out.

But having been there and done that myself, IMO you'll be much better off in the long run to swap transmissions.


Sent from my iPhone using Tapatalk
 
What are you running currently, stock 3.54 or optional 4.10?
I would first swap out the T-150 for a T-18 then address the gears depending on the type of trails you run.
 
With 35's-Look at 4:56.
You really need to think about a 4 or 5 speed tranny.
If you went to a 5 speed-Then 4:88 would be a better choice.
LG
 
I'm running 4.88s with 35" tires. I wouldn't want to go down the highway without Overdrive . Even tho these little 6 cylinders will turn up a lot more than we give them credit for, I still don't like to run them at a high rpm. I guess I'm old.

Sent from my LG-LS777 using Tapatalk
 
caveman said:
I'm running 4.88s with 35" tires. I wouldn't want to go down the highway without Overdrive . Even tho these little 6 cylinders will turn up a lot more than we give them credit for, I still don't like to run them at a high rpm. I guess I'm old.

Sent from my LG-LS777 using Tapatalk
Click to expand...

What Transmission do you have and do you drive it on the street or just trailer it?
 
I drive it on the street often. If I go offroading and know it's going to be rough I trailer it in case it breaks. The wife and I are touring the U.S. presently and I'm trailering it to save wear and tear. It's also our git around buggy while on the road. I presently have the AW4 automatic Transmission replacing an AX15 that was there before. This old fat body of mine doesn't bounce like it used to and creeping over an obstacle is more to my style.

Sent from my LG-LS777 using Tapatalk
 
caveman said:
I drive it on the street often. If I go offroading and know it's going to be rough I trailer it in case it breaks. The wife and I are touring the U.S. presently and I'm trailering it to save wear and tear. It's also our git around buggy while on the road. I presently have the AW4 automatic Transmission replacing an AX15 that was there before. This old fat body of mine doesn't bounce like it used to and creeping over an obstacle is more to my style.

Sent from my LG-LS777 using Tapatalk
Click to expand...

I plan on swapping a automatic in maybe 6 months.. you think 4.56s or 4.88s for now and later?
 
wooderson64 said:
I plan on swapping a automatic in maybe 6 months.. you think 4.56s or 4.88s for now and later?
Click to expand...
I went with the 4.88s because I do some rough offroading from time to time and not usually in a hurry when I take the Jeep down the road. If you're going to do mostly offroading the 4.88s might be what you want. Otherwise I would go with the 4.56s. It will still be very capable with 4.56s with an automatic.

Sent from my LG-LS777 using Tapatalk
 
FWIW, I had a set of 35s, which were aired to 28 p.s.i. for the street. I was getting around 3 grand r.p.m. at 60 m.p.h. This is with my T-18 tranny and 4:10 gears. I you compare this with those tire size/r.p.m. charts you can get online, it will show a lot less r.p.m. Although like I said, I only had 28 p.s.i., which makes the tire radius smaller.
 
Torxhead said:
FWIW, I had a set of 35s, which were aired to 28 p.s.i. for the street. I was getting around 3 grand r.p.m. at 60 m.p.h. This is with my T-18 tranny and 4:10 gears. I you compare this with those tire size/r.p.m. charts you can get online, it will show a lot less r.p.m. Although like I said, I only had 28 p.s.i., which makes the tire radius smaller.
Click to expand...

Interesting..I'm running 4.10 (actually 4.11 in the rear) on 35s (KM2s @ 30 psi) with a T-18 and I'm about 2500 rpm @ 60 mph
 
Torxhead said:
Well then I would say we have different speedometer gears in the Transfer Case .
Click to expand...

Maybe...Is your speedometer way off? Mine is within a couple MPH of GPS. sounds like your 60 mph may have been closer to 70 mph.
 
You must log in or register to reply here.

Jeep-CJ Donation Drive

Help support Jeep-CJ.com by making a contribution.

Help support Jeep-CJ.com by making a contribution.
Goal
$200.00
Earned
$0.00
This donation drive ends in
0 hours, 0 minutes, 0 seconds
  0.0%
Contribute
Back
Top Bottom