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I have a 1981 gas 4x4 and need to know the gear ratio for the transmission , rear end and transfer case. Any information will be appreciated.

check with 800xl.. i sent him all this info a while back

81 4x4

axle ratios: 4.10

Tcase LOW: 1.87

Trans Gears
1st: 3.79
2nd: 2.18
3rd: 1.42
4th: 1.00

Speedo gear is 6/20

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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)

MEPR: Man, my 4x4 makes all other LUVs look good

Oh yeah, woo me, 2000 posts!

Tcase HI is 1.00 by the way

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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)

MEPR: Man, my 4x4 makes all other LUVs look good

'79 4x4 gas short bed? Axle gear ratio specifically.

Is there no differentiation between models?

That one I don't even have to look up, all the 4x4 LUVs shipped with 4.10 axle gears, 79-82. There are some differences between models, like in 79 the 2WDs (stick and auto) had 3.73, and in 81 2wd 4spds had 3.42 and autos had 4.10.

At this point though you really can't assume anything about the gears in a particular truck though. 4x4s generally still have 4.10 gears since that is all I have been able to find for the front axle, but it is still possible someone swapped in something else for a rear axle, even if they couldn't change the front to match. It is also very possible that the old service manual data (source of the info I quoted above) is not 100% accurate. I'd say for the most part it is right, but there are always oddball parts that slipped out the factory door. Like "let's use up those axles from last year's model real quick, then start shipping what we're supposed to" and that sort of thing.

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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)

MEPR: Man, my 4x4 makes all other LUVs look good

True. I noticed there was no door sticker w/ parts codes like my Explorer has.

I guess the only way to truly know would be to pull the cover and check the pinion.

You could always jack up one tire, put the truck in neutral, spin the rear wheel 10 times, and count the number of revolutions of the driveshaft.

4.1ish will give you 41 revs.
3.7ish will give 37 revs.
and so on.

Of course if you want to know whether you have 4.10 or 4.11, you'll have to spin the rear wheel 100 times and hope you don't lose count of the driveshaft.

Just make sure the other tire is firmly on the ground.

I have an 81 pup diesel that came with a 3.42 rear and 5 speed. I bought an 81 luv 4x4 diesel and put the cab and box on the pup. When the 5 speed got noisy I took the four speed from the 4x4 and put in the pup. I also have an 81 gas that had a 3.23? It was around 3 1/4 turns on the yoke to one turn of both wheels. If I remember right, just jacking up one wheel you are going through the spider gears and will be way off. I came up with a little taller ratio than the 5 speed with the 3.42. That is with 7.00 x 14 tires instead of the smaller stock size. I wouldn't have used the bias ply tires instead of radials, but they were new and free. It is alright here on flat ground, but I wouldn't want to get it in hill country.

If any one know of a good cab or parts truck within 500 miles of Houston, let me know.