3.73 or 4.11?

[SeaComms]

So what ratios does the 08 diesel have as stock? I thought they were already on 3.73?

[Pete_m]

I have an 08 manual CRD. At the moment on stock 32's. From what you said about touring not hard core 4wding I will have do disagree with Bill from DBOR, I think the auto with it's longer over drive it is fine with 4.56's but the manuals have lower gears, the first gear in the manual is 4.46:1 and the auto is 3:1 where as over drive in the manual is 0.84:1 and the auto is 0.67:1

When i had the standard ratios I sat on 1800 rpm at 110, now I sit on 2480rpm and fuel is up a few L/100, from my calculations I should sit on around 2200 at 110 with 35's

I got my gears from DBOR, if you said all you do is hard offroad work then I would say go lower as the 4.11's and 32's are awesome offroad, but suck on the highway so bigger tyre with loose a bit offroad but be better on road making a good compromise

[vk2icj]

Here is the formula for figuring out your RPM's (thanx Seacomms)

Diff ratio x 0.84 x 1 x 209 x km/hr) / tyre diameter inches = RPM

using this with 4.56

4.56 x 0.84 x 1 (duh this doesn't change anything) x 209 x 110 / 34 =
2590 rpm

I chased this up myself last year and in the end went with the 4.88 From DBOR. Bill's customer service is second to none so you won't go wrong. I haven't installed the gears yet because I wanted to do lockers at the same time and numerous other Jeep projects have taken precedence but even with stock 31's 100km/hr is only 2763 RPM with 4.88s. It all depends on where you think you will be driving most. Most of my big trips average no more than 80km/hr. I most certainly will appreciate the lower gears and not miss the high end. It's a Jeep not a Ferrari

Chris

Originally Posted by double black offroad

4.11s are not the way to go in my opinion. Low range is still poor and with a manual, you will still be giving a bloody expensive gearbox and clutch a hard time which they dont like.
4.56 would be the minimun I would run.

Oh and we sell em too.

I ran 4.11s on my 07 on 33's the engine breaking was crap.

[EugeJK]

2600 rpm is too much for cruising. after 2600 max torque drops on this engine and at 2700 rpm i can hear injectors start ticking.
i run stock 32" and changed from 3.21 to OEM 3.73, perfect for city cruising unladen. mine's 6-sp 2-door. highway is 7.5-8L, city 12.5L, combined 9.2L, all unladen.

4.1 would be good, but if u need to tow, 4.56 would be better on 34".

no idea why ppl think 4.1(or 4.56) is better then 3.73(or 4.1) for offroad. makes no difference in 4L (divides extra by 2.7).

[wranglertj]

i find the 4.11's with a manual running 35's excellent for offroad. I reckon 4.56 would be good but IMO 4.11 breaks really well on 35's and works a treat offroad. My only gripe is towing and starting off the lights i think 4.56 would be better

[WHHEMI]

Originally Posted by EugeJK

2600 rpm is too much for cruising. after 2600 max torque drops on this engine and at 2700 rpm i can hear injectors start ticking.
i run stock 32" and changed from 3.21 to OEM 3.73, perfect for city cruising unladen. mine's 6-sp 2-door. highway is 7.5-8L, city 12.5L, combined 9.2L, all unladen.

4.1 would be good, but if u need to tow, 4.56 would be better on 34".

no idea why ppl think 4.1(or 4.56) is better then 3.73(or 4.1) for offroad. makes no difference in 4L (divides extra by 2.7).

I really dont understand your last statement can you please explane

[Pete_m]

Originally Posted by vk2icj

Here is the formula for figuring out your RPM's (thanx Seacomms)

Diff ratio x 0.84 x 1 x 209 x km/hr) / tyre diameter inches = RPM

using this with 4.56

4.56 x 0.84 x 1 (duh this doesn't change anything) x 209 x 110 / 34 =
2590 rpm

I chased this up myself last year and in the end went with the 4.88 From DBOR. Bill's customer service is second to none so you won't go wrong. I haven't installed the gears yet because I wanted to do lockers at the same time and numerous other Jeep projects have taken precedence but even with stock 31's 100km/hr is only 2763 RPM with 4.88s. It all depends on where you think you will be driving most. Most of my big trips average no more than 80km/hr. I most certainly will appreciate the lower gears and not miss the high end. It's a Jeep not a Ferrari

I'm assuming you have an auto and 35"+ tyres other wise with 4.88's it's going to rev it's gust out



As for 34's at 110 doing 2590 rpm I think that's too high for the CRD, that's why I went for 4.11's mine revs at nearly that at the moment and it's not very nice