Re: AMC Jeep 2.5 FI in Spirit?

[farna@xxxxxxx]

Tom, I posted the gear ratios as used in late model Jeep Cherokees with the same engine. The AX-5 and AX-15 have different gearing than the T-5 used in AMC cars. I'm not sure what the first gear ratio is in the AX-5 and AX-15 off the top of my head, but they are indeed used with 4.10 gears in 2.5L Jeep Cherokees. So Jim and I are neither wrong nor incorrect -- neither are you. Just talking about different transmissions in different vehicles. The question was on using the Jeep combo in a car, not running the Jeep engine with a car T-5. 

I'm pretty sure the axle gearing is about right when using the Jeep engine/trans combos. I tried running a 3.07 in my 4.6L with the Jeep AW4 auto with poor results. My Classic wagon weighs no more than a Cherokee, and has about the same frontal area. It doesn't take much to get more aerodynamic than a Cherokee though, and I'm sure the 63 Classic is a little better, but not much. Mileage suffered with the 3.07 gearing instead of getting better. I got it back when I switched to 3.55 gears -- the same as used in 2WD Cherokees. I always thought my Cherokee (when I had one) would be better with 3.31 gears, and I ran 3.31 gears when I was running the manual OD trans with good results. If I end up changing gears again that's what I'll use in the wagon. But dropping the gear to get better mileage doesn't always work. Depends on the trans gearing. A Spirit is a bit lighter and has a lot less frontal area than a Cherokee, so it should be able to handle less gearing and get a bit bette!
 r mileage. 3.54 might be pushing it with the Jeep trans though -- 3.73 should work well. You are correct -- the tire size makes a big difference! That's how I fine tuned my car to get the cruise speed I wanted. 


On September 26, 2005 Tom Bunsey wrote:

> Frank (and a couple others) posted concerning rear axle gearing.
> 
> AND THEY ARE WRONG (or maybe simply incorrect)
> 
> Eagles & SX-4 with the IRON PUKE and the AMC 4-cylinder (late 1983) had 3.54 axle gearing, and there were no "factory" axle options.
> 
> Spirits & Concords with the IRON PUKE used 3.08 with all tranny options (4-speed, 5-speed and automatics).
> 
> The AUDI 4-cylinder engines used 3.08 & 3.31 with the 4-speed, and 3.31 & 3.58 with automatics.
> 
> 4.10 gears in a street car would result in a real "granny" 1st gear, and pretty much negate any advantage of the overdrive 5th gear.
> 
> The Lister that suggested 4.10 gears stated he was eunning 30" tall tires in his Comanche, where such tall tires would need such a gear.
> 
> But, 205/70R14 tires are about 25-1/2" tall.  BIG DIFFERENCE (no pun intended).
> 
> I've driven a 1982 Spirit with the IRON PUKE and a 5-speed. It was pretty peppy, and it got 30+ MPG!  If you are looking for gas mileage, I suggest similar ratios to what came stock (i.e., 3.08).
> 
> Tom Bunsey


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