Topic: Jeep TJ Axle gear ratio's (Read 5177 times)

David Cheek · « **on:** January 24, 2017, 07:05:14 PM »

Hi can somebody help, I have a 1998 TJ with a 4 inch lift running D44 rear axle and a D30 on the front the wheels are 16 inch with the tyres it sits 31-32 inches to the top of the tyre, both axles have lockers in them, after 2 years of trialing and off roading the front axle needs rebuilding.
I managed to find a cheap Cherokee with a D30 high pinion axle, ratio is 3.54, my original ratio is 3.07.
The plan is to fit the Cherokee D30 front axle, and i believe this is a straight swap after i have added some strength to the lower control arm brackets and the upper bracket on the axle tube. The question i have comes in three parts.
1. I would like to regear both axles to 4.10 or higher, but cant afford to spend that amount on the jeep at the moment, so I'm planning on regearing the rear D44 to match the front - 3.54 will I notice any difference, on the road and off roading in low gear.
2. Or would you change the ratio of the D30 to 3.07 as I have it on the bench?
3. Once the D30 front axle is sorted and ready to fit, can I drive the jeep with different ratios, 3.07 rear and 3.54 front if I dont put it in 4 wheel drive? The reason for asking, I'm visiting the USA in March and plan on buying the parts needed for the ratio change then.

Thanks DC

Ezz · « **Reply #1 on:** January 24, 2017, 08:21:30 PM »

1, yes you should notice a slight difference in the gearing,

2, no, 3.07 is a bit high for 32" tyres anyway.

3, I'd think it would be ok if you keep it in 2wd,

Personally I'd leave it as it is until you've got all the parts to do a 4:10 rebuild to both axles..

David Cheek · « **Reply #2 on:** January 25, 2017, 08:37:13 AM »

Thanks for you help, I would love to do the 4.10 ratio change, as i understand it I will need the following parts, can you confirm?
1. D44 - 4.10 crown and pinion
2. New carrier
3. Fitting kit

4. D30 - 4.10 reverse cut crown and pinion
5. New carrier
6 Fitting kit

If I do the 3.54 ration swap on the D44 I will only need the following parts.
1. D44 - 3.54 crown and pinion
2. Fitting kit.

Ezz · « **Reply #3 on:** January 25, 2017, 01:45:55 PM »

Sounds about right...

gazjeep · « **Reply #4 on:** January 25, 2017, 04:31:06 PM »

RE-geared our 98 TJ some years back with 4.10 front & rear.

As I recall you don't need new carriers, bought all the parts here https://www.ringpinion.com/ & fitted True Trac LSD's front & rear.

Not sure, wait for a proper expert to post here but I think to run with different ratio's even in 2WD you will have to remove the front prop as you will FUBAR the transfer case. Even though not driving the front axle in 2WD, the prop is still turning.

Please DO NOT USE it until a clever bugger confirms or denies its safe

bgbazz · « **Reply #5 on:** January 25, 2017, 04:55:56 PM »

100%. Don't invite possible problems.

Ezz · « **Reply #6 on:** January 26, 2017, 05:39:17 AM »

Quote from: gazjeep on January 25, 2017, 04:31:06 PM

RE-geared our 98 TJ some years back with 4.10 front & rear.

As I recall you don't need new carriers, bought all the parts here https://www.ringpinion.com/ & fitted True Trac LSD's front & rear.

Please DO NOT USE it until a clever bugger confirms or denies its safe

The true trac LSD's were your new carriers Gaz..

The Smiths · « **Reply #7 on:** January 26, 2017, 07:37:09 AM »

or even look at getting a D30 from a 2.5L petrol cherry - already 4.1, then just regear the rear to get the gearing you actually want??

gazjeep · « **Reply #8 on:** January 26, 2017, 09:25:30 AM »

Quote from: Ezz on January 26, 2017, 05:39:17 AM

Quote from: gazjeep on January 25, 2017, 04:31:06 PM
RE-geared our 98 TJ some years back with 4.10 front & rear.

As I recall you don't need new carriers, bought all the parts here https://www.ringpinion.com/ & fitted True Trac LSD's front & rear.

Please DO NOT USE it until a clever bugger confirms or denies its safe

The true trac LSD's were your new carriers Gaz..

Told you there would be a clever bugger along soon

I just remember before going down the True Trac route I'm sure Lighty's said I would need new carriers going to 4.10 but others said I wouldn't ..... apologies, thought it was the carriers but could have been something else .......... I'm muddled with the passage of time

Getting back to the original question though, on a TJ can you really run 2 different ratio's in 2WD ? .......... Surely the transfer case would be buggered so you would need to disconnect the front prop ?

The Smiths · « **Reply #9 on:** January 26, 2017, 09:52:15 AM »

It is fine to run in 2wd with different ratios or different sized tyres to the rear- there is no "diff" in the transfer box - just a sleeve that locks it into 4wd when pulled into 4wd

Ezz · « **Reply #10 on:** January 26, 2017, 01:18:59 PM »

gazjeep · « **Reply #11 on:** January 26, 2017, 04:45:38 PM »

Nice one gents

That's most useful info

bgbazz · « **Reply #12 on:** January 26, 2017, 06:05:04 PM »

Just so I can get my head around this...if the freewheeling hubs are unlocked and you are driving in 2WD, the axles, diff and front drive shaft are not rotating...am I on the right track?

David Cheek · « **Reply #13 on:** January 26, 2017, 06:14:58 PM »

Well Gents thanks for all you help, all I have to do is get on with it now...

gazjeep · « **Reply #14 on:** January 26, 2017, 06:24:12 PM »

Quote from: bgbazz on January 26, 2017, 06:05:04 PM

Just so I can get my head around this...if the freewheeling hubs are unlocked and you are driving in 2WD, the axles, diff and front drive shaft are not rotating...am I on the right track?

I must be honest, as far as I know, there are no free wheeling hubs standard on a TJ, hence even though 4WD is not selected, the axle & prop are still rotating in 2WD so would stand to reason that the front & rear props would be spinning at different rates with different ratio's.

However, I have bugger all knowledge of the workings of the transfer case so defer to the knowledgeable ones

JamesH · « **Reply #15 on:** January 26, 2017, 06:55:36 PM »

Got it right though Gaz!

bgbazz · « **Reply #16 on:** January 27, 2017, 05:52:32 AM »

Thanks Gaz.

Delk · « **Reply #17 on:** January 27, 2017, 11:11:55 AM »

I thought all TJ's with D44's came with 3.73 gears already? At least mine did in the states. The 3.07's only came with the D35 rear end.

Driving around with different ratios in 2wd will not hurt the case. I have an old school D44 front with hubs and when they are unlocked the drive shaft doesn't spin at all. But if you do have different ratios you will probably want to stick it into 4wd at some point and have major issues.

JamesH · « **Reply #18 on:** January 27, 2017, 12:11:11 PM »

Some people have removed the front prop in this situation just to avoid a lapse in concentration causing lots of problems and costly damage - it only takes a second to shift it into 4wd and the bangs, pops and crunches will start all too quickly!

wildwood · « **Reply #19 on:** January 27, 2017, 01:24:35 PM »

A word to all, after going to 35s with 4.54s it became obvious that 4.88s are the ones to have....which is as low as you can go on a TJ Dana 30.

The maths might have it different but aerodynamics

and tyre weight count for a lot.
So my personal opinion would be
31-32 tyres 4.10
33s ............4.54
35s .............4.88

Anything bigger and axles parts will start breaking.....

Mike Pavelin · « **Reply #20 on:** January 27, 2017, 02:42:15 PM »

I used to run my XJ (4.0 manual like a TJl) on 31s with 3.73 and the gearing was spot on. any bigger than 31, and lower gears would have been in order.

Author Topic: Jeep TJ Axle gear ratio's (Read 5177 times)

David Cheek

David Cheek

David Cheek

Delk

Mike Pavelin