axles

Uffe · **Posted:** Sat Aug 02, 2008 2:29 pm

kdlewis1975 wrote:

Oh, I agree that adding a different gear would be a pricey proposition. But since we're talking about cost, you have to consider the price of buying another vehicle and paying for the cost of taxes, title, and insurance on a yearly basis. When I bought the CRD, I was single and I intended it to be my do-it-all vehicle. I thought it would be something that had the potential to get 30 mpg highway and therefore would be an acceptable vehicle for a 20 mile commute to work. Rather than own a separate truck for hauling things for the house I just bought, I figured I'd find a utility trailer so that I could have a miniature tractor/trailer combination. I also wanted something 4-wheel drive since it snows an appreciable amount here, and I attest that the ESP works very nicely.

I was in your situation 9 months ago. My girlfriend and I decided that we couldn't come to a compromise on houses, so we would stay in our flat, and I went out and bought the KJ. What I hadn't thought about was the future. I should have thought more about my work commute increasing from measly 31 to 60 miles per day. I knew it would happen, but I just didn't think enough about it. I already had a '95 Nissan Patrol which would cover my offroading needs just fine. There were some repairs which needed to be done, and I used them as an excuse to buy a newer car. What I really wanted was the 2.8 CRD engine, man that sound is just terrific, don't you think?

So 3 months ago the girlfriend suddenly changed priorities and wanted to buy a house. Me being foolish enough to buy the KJ promised her at its purchase that I would sell it if it would hinder our economy to cope with a house. So I needed to sell it briefly after I had bought it. Reality lesson learned here is:

Keep that old bugger of a car, get a second one which is way more economical. Do the soddy repairs and use the old car until you can see through the floor.

The value I lost on the KJ (because 4wds were suddenly not popular anymore, and fuel prices starting to rocket) amounts to a whole Nissan Patrol from 1995!! I could have kept the Nissan and bought the Fabia directly, and I would still have had more money in my pocket right now. Geez I learned that the hard way

kdlewis1975 wrote:

Since I bought the Jeep, I've bought a house, I've gotten married, I have a daughter on the way, and I can't exactly afford to add a third car at this point. My wife's vehicle brought to the marriage is a 2006 Suzuki Grand Vitara...talk about underpowered and poor fuel mileage. Unfortunately, both are too new and have too much negative equity at this point, so a trade-in isn't exactly and option at this point. I've perused the auto listings and you just don't find a VW TDI in this area for a low price that isn't already very old and/or ragged out. When I bought the CRD, I also expected to keep it for a very long time and with the price of diesel, a couple of MPGs better would pay off over the long term. One could also argue that making the engine turn fewer revs would also add to the longevity. CRD owners often remark that they get their best economy when they keep the tach under 2000 RPM. At 70 mph, my tach reads 2050...my speedo reads about 2 mph too high. I generally see about 27 mpg at 70-75 mph and 28-30 at 60 mph. It would seem that the best way to get a taller gear would be to simply change the gear instead of spending the money to put on bigger tires and a lift to accommodate them....it's not like this is necessarily inexpensive either. The aero issue is a whole other debate...doing the lift probably increases the drag...changing a gear doesn't.

If I was serious about adding new gears, I'd go to a junk yard and find wrecked Libby with a manual (see Wikipedia link below). Going "used" would probably be the most economical route to go. I still wonder if there would be a problem for our ESP equipped Libby's. I did wonder about what one could do about the shift points and recalibrating the speedo.

http://en.wikibooks.org/wiki/Jeep_Liberty/Gearing

These two links are actually from the above Wikipedia page, they could be interesting to play around with.
http://www.novak-adapt.com/knowledge/gearing.htm ...tests gearing scenarios
http://www.4lo.com/calc/geartable.htm ...relates tires sizes and economy

Thanks for the nice discussion thusfar....

Yep see above - my life changed as well. I'm sorry that you can't sell the Liberty because of your needs and your current economical situation. I decided to take the enourmous hit and get my economy balanced out. For every mile I drive I save 16 cents in my Fabia compared to my KJ. In 75,000 miles I will have saved my loss on the KJ

I'm sorry if I come along here all over-zealous about doing fuel savings the hardcore way. I do find myself missing my KJ a lot, that might come out a little agressive against the people who still ride in them

My advice is do 60mph instead, the savings will be greater than going a gear up and still do 75mph. Talk yourself into it instead of spending more money on the KJ you really have a hard time affording in the first place. Learn from my mistakes, please.

Sir Sam · **Posted:** Sat Aug 02, 2008 2:34 pm

Uffe wrote:

kdlewis1975 wrote:

Oh, I agree that adding a different gear would be a pricey proposition. But since we're talking about cost, you have to consider the price of buying another vehicle and paying for the cost of taxes, title, and insurance on a yearly basis. When I bought the CRD, I was single and I intended it to be my do-it-all vehicle. I thought it would be something that had the potential to get 30 mpg highway and therefore would be an acceptable vehicle for a 20 mile commute to work. Rather than own a separate truck for hauling things for the house I just bought, I figured I'd find a utility trailer so that I could have a miniature tractor/trailer combination. I also wanted something 4-wheel drive since it snows an appreciable amount here, and I attest that the ESP works very nicely.

I was in your situation 9 months ago. My girlfriend and I decided that we couldn't come to a compromise on houses, so we would stay in our flat, and I went out and bought the KJ. What I hadn't thought about was the future. I should have thought more about my work commute increasing from measly 31 to 60 miles per day. I knew it would happen, but I just didn't think enough about it. I already had a '95 Nissan Patrol which would cover my offroading needs just fine. There were some repairs which needed to be done, and I used them as an excuse to buy a newer car. What I really wanted was the 2.8 CRD engine, man that sound is just terrific, don't you think?

So 3 months ago the girlfriend suddenly changed priorities and wanted to buy a house. Me being foolish enough to buy the KJ promised her at its purchase that I would sell it if it would hinder our economy to cope with a house. So I needed to sell it briefly after I had bought it. Reality lesson learned here is:

Keep that old bugger of a car, get a second one which is way more economical. Do the soddy repairs and use the old car until you can see through the floor.

The value I lost on the KJ (because 4wds were suddenly not popular anymore, and fuel prices starting to rocket) amounts to a whole Nissan Patrol from 1995!! I could have kept the Nissan and bought the Fabia directly, and I would still have had more money in my pocket right now. Geez I learned that the hard way

kdlewis1975 wrote:

Since I bought the Jeep, I've bought a house, I've gotten married, I have a daughter on the way, and I can't exactly afford to add a third car at this point. My wife's vehicle brought to the marriage is a 2006 Suzuki Grand Vitara...talk about underpowered and poor fuel mileage. Unfortunately, both are too new and have too much negative equity at this point, so a trade-in isn't exactly and option at this point. I've perused the auto listings and you just don't find a VW TDI in this area for a low price that isn't already very old and/or ragged out. When I bought the CRD, I also expected to keep it for a very long time and with the price of diesel, a couple of MPGs better would pay off over the long term. One could also argue that making the engine turn fewer revs would also add to the longevity. CRD owners often remark that they get their best economy when they keep the tach under 2000 RPM. At 70 mph, my tach reads 2050...my speedo reads about 2 mph too high. I generally see about 27 mpg at 70-75 mph and 28-30 at 60 mph. It would seem that the best way to get a taller gear would be to simply change the gear instead of spending the money to put on bigger tires and a lift to accommodate them....it's not like this is necessarily inexpensive either. The aero issue is a whole other debate...doing the lift probably increases the drag...changing a gear doesn't.

If I was serious about adding new gears, I'd go to a junk yard and find wrecked Libby with a manual (see Wikipedia link below). Going "used" would probably be the most economical route to go. I still wonder if there would be a problem for our ESP equipped Libby's. I did wonder about what one could do about the shift points and recalibrating the speedo.

http://en.wikibooks.org/wiki/Jeep_Liberty/Gearing

These two links are actually from the above Wikipedia page, they could be interesting to play around with.
http://www.novak-adapt.com/knowledge/gearing.htm ...tests gearing scenarios
http://www.4lo.com/calc/geartable.htm ...relates tires sizes and economy

Thanks for the nice discussion thusfar....

Yep see above - my life changed as well. I'm sorry that you can't sell the Liberty because of your needs and your current economical situation. I decided to take the enourmous hit and get my economy balanced out. For every mile I drive I save 16 cents in my Fabia compared to my KJ. In 75,000 miles I will have saved my loss on the KJ

I'm sorry if I come along here all over-zealous about doing fuel savings the hardcore way. I do find myself missing my KJ a lot, that might come out a little agressive against the people who still ride in them

My advice is do 60mph instead, the savings will be greater than going a gear up and still do 75mph. Talk yourself into it instead of spending more money on the KJ you really have a hard time affording in the first place. Learn from my mistakes, please.

75,000 miles huh? Averaging 20,000 miles a year, thats almost 4 years to pay it back.......

Uffe we are talking about spending a few hundred dollars to change out gears and keeping the vehicle we have, I dont care to do the cost analysis on speculation - since we dont know what difference it will really make. But I suspect our changing gear ratios will prove to pay for itself back in a fraction of the time yours will.

warp2diesel · **Posted:** Sat Aug 02, 2008 9:40 pm

ABS sensors, no recalibration will be needed. I don't know how the ECM for the engine will take this though. If I were to do this to mine my RMS would drop from 2000 to 1898 at 70 mph by swaping out 3.73 for 3.54 axles. I will look at a torque curve for our engine and see if it has enough torque to do the job with the taller gears.
As our CRDs get older there will be more in the bone yard to pick from. But I suspect the people with gassers that have a manual trans love theirs as much as we love ours and will do all they can to keep them on the road.

Peak torque is at 1800 RPM (400nm) and the torque curve looks pretty flat up to 2500 RPM, below 1700 RPM it starts to drop off.

Uffe · **Posted:** Sun Aug 03, 2008 4:04 am

Sir Sam wrote:

75,000 miles huh? Averaging 20,000 miles a year, thats almost 4 years to pay it back.......

Uffe we are talking about spending a few hundred dollars to change out gears and keeping the vehicle we have, I dont care to do the cost analysis on speculation - since we dont know what difference it will really make. But I suspect our changing gear ratios will prove to pay for itself back in a fraction of the time yours will.

3 years to make up the loss on the KJ, not the cost of changing over to a TDI as a 2nd car. I lost $12,000 on depriciation which I will make up by driving a TDI compared to a KJ.

A few hundred dollars is no big price I agree - and if you go ahead with changing gears I am going to read what you find. It is interesting to me nonetheless.

My calculations were these:

On a yearly basis I pay $1,200 less on road tax for the TDI.
On a yearly basis I pay $4,000 less on fuel while driving 25,000 miles (16 cent per mile)
Insurance is nearly the same, just $300 difference.

Had I not had to pay insane amounts of money to have the KJ insured and the road tax for it I would have kept it!! I'll have to go back to an old Nissan to do my fun stuff

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

Installing a mod like this to save a few bucks on fuel in a Chrysler that depreciated something on the order of %40 of its value the moment it was driven off the lot does seem a little silly to me. And I am probably one of the most MPG obsessed people on the forum.

It seems to me that installing 3.55's in a the CRD is a double edged sword... our highway mileage is decent in stock form, but our city mileage sucks. Taller gearing will help the highway mileage by keeping RPM's down at speed, but will make the city mileage even worse (by making the engine work harder to get the 4500 pound Jeep moving). This is exactly what happened to my Jeep when I went from 225/75 factory tires to 235/75 Firestones.

Really, if fuel costs are such a big deal that you want to re-gear an SUV, you bought the wrong car. If you just want to do it to tinker and customize your rig, more power to you.

RedStapler · **Joined:** Fri May 11, 2007 10:04 am **Posts:** 77

DarbyWalters wrote:

Taller tires (very tall) will hurt aerodynamics. Adding a slightly taller tire will sometimes improve mpg after you adjust your numbers for the change. I went to 235/75/16s which made an ~4% diff in overall gearing which results in the same as throwing in a 3.58 gear set. Tires is the easiest and cheapest way to make a difference.

I'll be taking off the worn OEM 225 and going to 235 SR-A pulled off a Renegade in the next month or so. I'll keep the forum posed.

Larry R. · **Joined:** Sun Jan 21, 2007 1:35 am **Posts:** 92

A person could just swap a gear set in the rear axle and test the milage. If it improves replace the front too, if not reinstall the original gears.

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