LUVTruck.com

I scoured this forum for info and picked up some useful stuff. Here's info I can't find:
I'm looking at a 72 LUV in a couple days and need to identify the rear-end gear ratio, whether it's the 4.56 or 4.10. I ask because the transmission is an automatic in this particular 1972 LUV which I found out is definitely not the original tranny. 72's only had manual transmissions. I don't think the present owner has a clue about the history of the truck, so I want to see if whoever changed the tranny also changed the rear-end.
I want the simplest way to get the LUV as economical as reasonably possible for use as a "daily driver"; power/performance is not a concern. Using the calculator link I found on this forum, the engine would be running at 2971 RPM with the 4.10 rear at 55 mph and stock 25.5 tires, and 3305 RPM with the 4.56 rear. Do the rear axles have a number stamped on them which will indicate gear ratio? Getting the RPM lower would be great. What's the largest diameter tire that will fit a 72 LUV with no problems? Also, what's the simplest way of changing the gear ratio of the rear-end if I keep the present 1.8 engine and tranny? Is it a matter of swapping gears in the axle? I'm not very knowledgeable on the subject, and I have already searched this forum. Thanks!
Jeff

there should be a metal tag on one of the bolts for the rear end cover. it will have several numbers on it all you need to look for is 4.10 or 4.56 or what ever it may be. in my personal opinion its easier to swap out the whole rear end that way you dont have to worry about tryin to get all the little things perfect so it dont blow out in 50 miles

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zyanug
75 luv stepside... Work in progress
76 fleetside 350hp 1968 327cu
"No replacement for displacement!"
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[_@l__l__@_]***

I dont think isuzu ever put tags on there rear ends for the ratio. The only ways to tell would be pulling the pumpkin and counting the teeth or jack it up off the ground and have a buddy help hold one tire while you spin the other side. While your doing this count how many times the driveshaft turns for one turn of the tire. It helps to make a mark on the shaft somwhere for a reference point so 4 1/2 turns would be a 4.56. Sounds like maybe the body was swapped onto a newer frame. An easy way to tell between an early model frame and a later frame are the engine mounts. The 72-75 had the mounts closer to the steering box and the 76-80 had the mounts almost center in the engine compartment ( above the crossmember that goes under the oil pan). Also check if it has drum or discs up front, but there could be a possiblity though that it could have been upgraded to disc's at one point. If it looks like a later frame than it will more than likely have the 4.10 "auto" ratio.

If you want to keep the auto you could try to find an axle or just the pumkin out of a isuzu diesel pup Im pretty sure that they have a 3.42 ratio but I dont know if the auto would like that ratio very much.


Also have you seen this thread?
http://forums.luvtruck.com/viewtopic.php?f=5&t=2083

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1975 V8 Luv
1980 Bagged Luv

Yup, Isuzu had 3.42 ratio as well as 3.73, which might be a good compromise. You could probably build quite the gas mileage machine if that's your intent. You just might have to do a lot of work to it. If it's actually a late LUV drivetrain then its a candidate for a pup 5 speed swap, coupled with 3.73 axle, light right foot and a vacuum gauge you'd be about as good as you can get. You're right that the new trucks just don't have the mileage. BTW I just went out and measured my tires and they're only 24" tall. I'm planning on getting either a 3.42 or 3.73 rear end to help my mileage. You can find them on car-part.com for about $100.