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Actually the diesel gets great mileage stock. 30-33 mpg is doable at highway cruising.
What i'm looking for is extra power so it won't struggle so hard uphill with bigger tires.
I'd be fine with topspeed at 65-70mph if i could cruise with ease at 55-60.
Then I would shoot for 10 or 15 percent lower than the stock RPM at your cruising speed.
So if you turning 2000 rpm at 60 try and get 2200 or 2400 at 60 with the larger tires.
I don't know the power curve of the diesel or where they geared it from stock. You basically want it geared to hit a peak, or the peak, of the power curve at cruising.
What size tires are you running? It is generally accepted that 4:56 is a good ratio for 33's and 4:88 is a good ratio for 35's. Above that look at 5:xx.
Currently running 31's.
Obviously want to go bigger but i'll have to regear at the same time. I just don't want my already slow diesel to get even slower from the bigger heavier tires.
I'll have to do the math, but i kinda like the idea of 4:56 for 33's. Should give me slightly higher rpm/mph.
I'll be looking for an extra set of axles. Just so i can work on them without having to leave the xj stationary.
Currently running 31's.
Obviously want to go bigger but i'll have to regear at the same time. I just don't want my already slow diesel to get even slower from the bigger heavier tires.
I'll have to do the math, but i kinda like the idea of 4:56 for 33's. Should give me slightly higher rpm/mph. I'll be looking for an extra set of axles. Just so i can work on them without having to leave the xj stationary.
Been there, done that, and quite glad I did. I planned to get the axles under the XJ between Christmas and New Years - on vacation, it was my daily driver at the time. I ended up not being able to for a variety of reasons and could still drive to work on Monday because I had been working on the new set of axles.
How's the stock gearing on the diesels? I know the 4cyl gassers get a different gear ratio to put them back in the right spot on the power curve, but I've never even seen a diesel XJ so I'm not familiar with them. Did they get the same 3.55:1 that 6cyl automatics did, or something else?
Yep, as far as i've been able to find the diesels came with the same 3.55 as the I6. They're all manuals too, no autos. Suppose that might have something to do with it.
Yep, as far as i've been able to find the diesels came with the same 3.55 as the I6. They're all manuals too, no autos. Suppose that might have something to do with it.
They existed, but were ultra ultra rare, and the only two I know of I heard about from a local member... they are sitting in someone's private junkyard.
going to open this back up.
I called 4wheelparts today to get a quote on 4.88 gears for my D30 and 8.25 and they said they do not make them I have found them online.
So my question is why would they say they only make 4.56 for the 8.25
If i do buy them can they be used without special mods.
4.88s are some what new for the 8.25 something like ~2 years? The person you talked to probably just didn't search it correctley or they don't sell them there. I think motive is the only one with 4.88s for the 8.25?
4.88s are some what new for the 8.25 something like ~2 years? The person you talked to probably just didn't search it correctley or they don't sell them there. I think motive is the only one with 4.88s for the 8.25?
The only company that makes them is Nitro Gear and Axle. 4wp may not carry their parts, therefor no listing in the computer, retail monkey thinks it does not exist.
I totally agree.If they do not know that they are available for the cry 8.25 then they should be taking classes on ALL jeep parts!!! Like they do in court system.Manditory education!!!!
Yes this is true, and we have them in stock. Support your Naxja sponsoring vendor! We just donated a bunch of product to Naxja for giveaways at events.
The only company that makes them is Nitro Gear and Axle. 4wp may not carry their parts, therefor no listing in the computer, retail monkey thinks it does not exist.
Im at a crossroads, I am absolutely about to order some gears, D30 in the front, Ford 8.8 rear... but I'm not sure whether to do 4.56 or 4.88.
Jeep is 1998 Cherokee 4.0 Auto on 33's (measure pretty close to 33") E rated Firestone M/T's
I someday *think I will go to 35's, most likely the next tire change... but I could possibly not.. The Jeep will have Heavy, solid hex long arms, full crozzmember/skid, Frame rail stiffeners, 2x3 stage 2 JCR rockrails, and will eventualy get front and rear bumpers with a winch and a spare hanging off the back... plus it carries the wife, kid, and dog... so it does/will carry some weight!!!
My main concern is if for some reason I stay with 33's I dont want my jeep to be over working with the deep gears...
I also have a really high chance that i will build a 4.6-.7 stroker for it in the near future....
Go 4.88s with 33s. I just regeared my 30 and 8.25 to 4.88 with 33s and it is a lot better then my buddys 4.56 geared xj on 33s. It doesn't scream on the highway at all and im getting 19-20mpg give or take. It still gives you some room to grow to 35s if you decide to down the road. Trust me gears arent cheap so I'm sure you would rather have more power then not have enough right? Go deep and dont look back, you wont regret the 4.88 in the slightest bit.
Go 4.88s with 33s. I just regeared my 30 and 8.25 to 4.88 with 33s and it is a lot better then my buddys 4.56 geared xj on 33s. It doesn't scream on the highway at all and im getting 19-20mpg give or take. It still gives you some room to grow to 35s if you decide to down the road. Trust me gears arent cheap so I'm sure you would rather have more power then not have enough right? Go deep and dont look back, you wont regret the 4.88 in the slightest bit.
x2!! I've seen this question all over the place and the guys that go with the 4.56s always regret it. Especially if you are going to go with 35s or even eventually go 35s go with the 4.88s! Good Luck!!
