Just wondering if anyone knows aboutOver drive kits for disco 1's. @ 75-80mph i'm runnig at close to 3,000 rpm's. seems that by now someone would make a device to drop the rpms on the highway for better mpg. I searchedthe sight for old postings... but didn't seem to find anything.

 

Droping the RPM's won't improve mileage unless you are able to reset your whole power and torque curve.
Your rpm's aren't that high, mine are higher and I get nearly 18.5 on the road at 65 with my a/c off at 7000 feet here in Colorado.
If you want better mileage, think of things to do to your engine to tune some more mileage out of her.
What octane gas are you running, have you changed out your 02 sensors, how about your plug wires?
What sort of mileage are you getting now?
Based on our 4.0 engine size, low horse power and weight along with our already high 3:54 gears, you are looking in the wrong direction.

 

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I'm finding that I get BETTER mpg with the engine running in the mid to high 2000's rpm, and I have the 4.6 motor. But when I first got her I was thinking the same as you Jrock,eventhe 4.6sounds and feels like it needs an overdrive, compared to my Grand Cherokee anyway. But it seems that adding an overdrive (if there's even a kit available)might actuallyhurt your mpg, with less noise/more comfort being the only benefit.

 

Next time you need tires get 245/75/16 (31")
it will lower the rpm a little but I don't know if it will help.

 

Your Disco has overdrive, it is called 4th gear.
on your gear selector you will see 1=1st gear
2=2nd gear
3=3rd gear
D=4th gear