Swapping 4.10 to 3.54 final drive ratio
09-09-2009, 10:03 PM
#1
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Year: 1993
Model: Cherokee
Engine: 2.5L 4 cyl
Swapping 4.10 to 3.54 ring and pinion set
Howdy folks... I've got a '93 XJ with a 2.5L engine, AX5 5sp tranny and 4.10:1 final ratios. It has Toyo 235/75R15 Open Country A/T tires that measure 29.5" diameter. No other gear, rack, bumpers, etc. Bone stock except for the rims and tires.
I bought this rig to be a grocery getter with a little 4x4 "insurance" for the winter months. It'll never see any off road action other than some well traveled forest service roads around Idaho on occasion. The kind of roads I could drive my wife's 2004 Windstar on... I also make highway trips to Twin Falls, about 25 miles away on a regular basis and I drive about 65mph for the most part.
I would like to get a few more mpg out of this rig so I'm thinking about swapping some 3.54 ring and pinion sets for the 4.10 units.
Right now, according to this chart, http://www.800-923-jeep.com/techCorner/gears.cfm I'm turning around 2600rpm@55mph. By going to a 3.54:1 ratio, I should get the rpm's down to 2256 or so, a drop of around 350-400rpm.
My concern is this: I need to stay on the engine torque curve enough for just normal driving. I don't think the rpm drop will seriously effect the performance of the engine but I'd like second opinions if anyone would care to post 'em.
Any thoughts on this? Thx.
I bought this rig to be a grocery getter with a little 4x4 "insurance" for the winter months. It'll never see any off road action other than some well traveled forest service roads around Idaho on occasion. The kind of roads I could drive my wife's 2004 Windstar on... I also make highway trips to Twin Falls, about 25 miles away on a regular basis and I drive about 65mph for the most part.
I would like to get a few more mpg out of this rig so I'm thinking about swapping some 3.54 ring and pinion sets for the 4.10 units.
Right now, according to this chart, http://www.800-923-jeep.com/techCorner/gears.cfm I'm turning around 2600rpm@55mph. By going to a 3.54:1 ratio, I should get the rpm's down to 2256 or so, a drop of around 350-400rpm.
My concern is this: I need to stay on the engine torque curve enough for just normal driving. I don't think the rpm drop will seriously effect the performance of the engine but I'd like second opinions if anyone would care to post 'em.
Any thoughts on this? Thx.
Last edited by IdahoXJ; 09-09-2009 at 10:23 PM.
09-09-2009, 10:24 PM
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Year: 1987 Jeep Cherokee 4x4 4dr
Model: Cherokee
Engine: 2.5 liter 4cyl
Dont do it, I have the same xj, a 1987 with the same engine and trans.
I got on one trip up to south lake tahoe from where I live, "which would be about 250 miles", 22 mpg with four people and all there luggage on that trip.
I dont think you will get better mpg by doing that, you will bog down that 2.5 by gearing down, stick with the 4.10 gears they are what you should have with that set up.
I got on one trip up to south lake tahoe from where I live, "which would be about 250 miles", 22 mpg with four people and all there luggage on that trip.
I dont think you will get better mpg by doing that, you will bog down that 2.5 by gearing down, stick with the 4.10 gears they are what you should have with that set up.
09-09-2009, 11:02 PM
#3
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I would recommend not doing that. It would be the same as subtracting 14% of your horsepower, which I think you will agree you cannot do without. Jeep used the 4.10s instead of the 3.54s or 3.07s because the 2.5L and 2.8L are really a little underpowered for that size of vehicle.
09-09-2009, 11:29 PM
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Year: 2000
Model: Cherokee
Engine: 4.0
09-10-2009, 01:36 AM
#6
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I would recommend not doing that. It would be the same as subtracting 14% of your horsepower, which I think you will agree you cannot do without. Jeep used the 4.10s instead of the 3.54s or 3.07s because the 2.5L and 2.8L are really a little underpowered for that size of vehicle.
09-10-2009, 08:08 AM
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Year: 1993
Model: Cherokee
Engine: 2.5L 4 cyl
Hmm, yeah, 14% is a lot to lose... Thx for the feedback guys.. I guess I'll look at some other ways to squeeze a bit more mpg out of my rig....
@Jonny and Paco... sorry guys, no trades but thanks for the offers...
Cheers.
@Jonny and Paco... sorry guys, no trades but thanks for the offers...
Cheers.
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