LUVTruck.com

I'd like to change the gear ratio to get my GM V6 powered LUV to be able to cruise a little easier.

What I have:

Buick 3.8L V6 engine
GM th350 Auto tranny
Stock 4.10 rear end

The Speedo/Odo's are way off, rough estimate is that the LUV thinks a real mile is something more like 1.4, and that a real 60mph is right around 75...

If the final drive brought the speedo/odo into a more accurate range, the rig would be perfect.

However, I'm not a mechanic that can customize, and am not interested in spending a couple grand to hire the work done, as it would be twice what I paid for it...

So are there any other differential sets that can be bolted in without a custom driveline, or changing the full axle/diff/case combination, or requires shortening, or anything like that?

Looking for just a straight forward drop the rear, pull the diff, change the gears, bolt it back up option. Or pull the diff, and swap with another that bolts right back in.

Any chance of it being that easy at all? (And if it is, any idea how to figure out what diff ratio would be the right one?)

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1978 shortbed fleetside, th350, Fireball 231 Even Fire V6, Edelbrock 500CFM Performer with Edelbrock intake. Workin' Truck.

4.10 is the gears that come with the automatic luv
4.56 is what come with the manual trans i think.

Not sure what you mean by "cruise a little easier". If you mean turn a lower RPM at freeway speeds I think you would have to hunt for a different ring gear and pinion. If they exist. since you have the 4.10's you have the best stock offering for that.

another crazy Idea would be to use the biggest diameter tire that you can fit in there. each rotation of the tire would let you cover more distance and turn a little lower RPM. You could probably do the math to see how much rpm less on the engine this would give you.

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Did a v8 conversion in 1981 on my '76 luv
Current Fleet
#1 1980 Black 2wd, #2 1980 Blue 2wd, #3 1980 Black 4x4 #4 1980 black 2wd Long bed #5 1979 black 4x4 #6 1977 red 2WD
pics
http://s137.photobucket.com/albums/q223/gs11x/

if your wanting to just switch out the center section, got to the junk yard and look for 83-87 diesel pups. they had 373s and sometimes 342s. they also use the same rearend, so all youve gotta do is swap the sections, and your good to go.

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"but its that gut feeling of you're drawn to what feels right for yourself and what you're passionate about..."

OR you can change the speedo drive gear to correct the error,but then again i like the 3.42 gear idea to.

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

wouldn't it just be easier to go with the s10 rear end?
what kinda of gears did they have?

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On the search for another Luv Machine

the s10 rear would be more work and more money then just swapping a centersection.

the s10 rears came with 273s 308s 323s 342s 373s 410s and 456s.

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"but its that gut feeling of you're drawn to what feels right for yourself and what you're passionate about..."

In the later luv 2wd models, they had a higher gear ratio that was way better than the lower ratio earlier 2wd ones.

But if you are running a V6 and and a GM aotomatic and want a rear-end to last, you might look at getting a newer rearend out of an 86-88 isuzu pup, have a ford 9-inch re-done, or find one you can adapt to six lugs out of a chevy monza that had a v8.

The early stock luv rearends were way too low geared and won't handle a lot of power from a bigger engine and a bigger automatic without going to hell on you when you try to seriously light your tires up.

Your cheapest and easiest fix would be the rearend and a driveline from a newer 86-88 isuzu truck, preferrably one with the 2.6 motor.

Then the worst you might have to do is swap out your rear springs, and then swap out your rearend yoke to it or change the rear piece of your driveline to match.

Although on both trucks, the rearend yokes have different bolt patterns and the front driveline yokes have different splines, the u-joints are all the same and the rearend pinion yokes will interchange from one to the other too.

About the only real fabrication you will encounter is removing the little metal tab that the brakeline junction box bolts to on the isuzu truck rearend and re-welding it to the other end of of the rearend housing to match your stock luv brake lines.

But the isuzu truck's brakes, brake lines, e-brake setup, lug bolts, etc. and everything else will work on your luv.

So as long as you get the same length driveline for the same length bed you have from the newer isuzu truck, with just a little parts swapping you will have an easy job to do and be back on the road in no time.

BTW...no offense meant, but take it from an old timer...if you are going to drive around in an older classic car or truck that has been customized and modified to trick it out....then you better get some tools, find a garage to work on it in, buy some manuals, and sharpen up your mechanical skills.

You see...most auto repair shops don't have the skills and the knowledge, don't have the right tools and equipment, or just plain don't like to fool around with older custom cars and trucks....and the ones that do are not going to be cheap at all. (And even some of them will end up hosing you or doing poor quality work.)

Because older custom hot rods are meant for folks with a lot of tools, skills, and free time, plus some serious mechanical skills, that like to spend a lot of time tinkering on them in their own shop or garage....and if you aren't that kind of person or don't want to become one...then you are driving someone else's truck.

You just haven't sold it to them yet...lol

Just my $.02 worth...I hope this helps you.

This is what I was hoping for...

Thanks Joe! I'll look into it.

Yes, I could fix the speedo, but I'd like to get the higher ratio...

And I'd heard about changing to a S10 rear, but that requires fabrication, a driveline, rear axels, and other stuff I don't really want to think about...

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1978 shortbed fleetside, th350, Fireball 231 Even Fire V6, Edelbrock 500CFM Performer with Edelbrock intake. Workin' Truck.

Taz, thanks for the tips and additional info.

I now have:
Haynes for '78 buick
Book on the th350 tranny
Haynes for LUV
78 LUV Chevy Shop Manual (and shop manuals for series 2,4,5,6 for sale)

I do have tools, but would prefer to do the minimum changes to maintain driveability and usefulness. It's a rat rod... pretty ugly.

I don't plan on lighting up the tire (hard to spin both without an LSD).

I'm not worried that much about turning a wrench, but plan to avoid as much major modification as possible.

Sorry, I'm selling the M3, planning on keeping the truck...


Smart @$$... LOL!

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1978 shortbed fleetside, th350, Fireball 231 Even Fire V6, Edelbrock 500CFM Performer with Edelbrock intake. Workin' Truck.

So, this would be the appropriate item, no?

1986
Differential Assembly
Isuzu Truck Mini Pickup

342 GEARS

$125 (plus shipping) from a place in Alabama...

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1978 shortbed fleetside, th350, Fireball 231 Even Fire V6, Edelbrock 500CFM Performer with Edelbrock intake. Workin' Truck.

yeah, thats the one! wow, you find parts fast!! lol

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"but its that gut feeling of you're drawn to what feels right for yourself and what you're passionate about..."

Hey...I'm certainly not trying to piss anyone off here.

And I humbly apologize if I've offended anyone here ...but you all know as well as I do that this place does have a bunch of folks hanging around here that don't want to get their hands dirty working on their own truck, don't want to learn anything about their truck, don't want to listen, don't own any tools or want to spend any money, and especially are way too damn lazy about looking stuff up that is already been posted here.

Ben built this place, we all try our best to help support him, and it is all been done for those of us that want to show up each day to help and support each other....not for the people that come here and just want to whine and cry about their gutless crappy running slow-ass old trucks...because in case anyone didn't tell them before they bought it, we regular members here already know that's how a stock old beat up worn out Luv is....lol

A good example of this is the guy I sold my old 78 longbed Luv to. I spent countless hours in my garage while I fixed all of the running gear up, fixed up the body and re-painted it, put in a nice stereo, plus I added new seats, a good canopy, nice wheels and tires, and all new carpet...then I gave him a real good deal on it when I bought my 79 shortbed.

And how did he thank me?

He drove it around for over 6 months bar-hopping without changing the title, treated it like a rolling garbage can, abused the hell out of it and drove the poor thing like it was a freakin' battle-tank, and everytime it had a problem or broke down...he took over my garage and yard for weeks with it sitting in my damn way because he was just too damn lazy or too cheap to bring his butt over and use my tools and garage to fix it himself.

That eventually cost him his employment with me, his welcome around my place, our friendship, and now his truck is sitting broke down because it needs a simple minor repair (just like the last car he was driving before he bought my old '78 Luv is) - right outside his apartment door. And of course now he is bad-mouthing me all over town, rather than taking responsibility for everything he did or admitting at all that he screwed up....and still has the nerve to bug me constantly about when he can bring them both over so I can fix them for him (for free of course), and has even tried numerous times unsuccessfully to borrow money from me to go out partying.

So...I didn't mean to take anything out on anyone specific here, and if it felt like I was...I'm really sorry.

Now I'll just finish my little rant with these last little comments...and then I'll shut my big trap and let you have your thread back.

...For those of you that are willing to put in the time, money, and effort to fix up your Luv while making good use of this site and it's great members...I applaud the hell out of you, and I will gladly help you in any way I can.

...And for those of you whiners here or anywhere else that aren't...it's probably best that you avoid contact with me from now on.

You see...the things I would really like to say to you whiners, Ben doesn't allow us to post here, but I would certainly have no problem at all saying that to any of you annoying numbnuts up close and personal, face-to-face...lol

Well done Taz hoo ra

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

Taz,

No offense taken, and I agree with your comments.

(snarky remark follows - grains of salt included here: ... )
Can I still call you smart @$$?

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1978 shortbed fleetside, th350, Fireball 231 Even Fire V6, Edelbrock 500CFM Performer with Edelbrock intake. Workin' Truck.

Holla back at the ole' Tazman whatever you want...ya'll know when I hears ya...lol

Just a bit more info and another option, the Isuzu Impulse used the same 10 bolt isuzu rear end. They all should be 3.90 gears, and The turbo models all came with the LSD. Look at the option code plate on the firewall for code G80 on non-turbo Imps to find an LSD rear. You want to look at them though, the 85s had this funky torque tube setup, so the input yoke on the diff is a couple of feet from the actual diff. You won't be able to swap the whole axle(no leaf springs, 4 lugs), but I believe you can unbolt the third member and just drop it in. I'm not sure what the driveline situation will look like, especially with the trans you have in there now. I think the 88 Imp parts car I have has the same bolt pattern as the LUV, I'll have to check.

I don't know what kind of HP you are getting out of that V6, but the stock Impulse runs about 140HP through the LSD rear in a turbo car. Sure it isn't going to hold up to racing slicks and wheelstanding takeoffs, but you could get quite a few miles out of it.

The complete Isuzu 12 bolt axle like Taz is talking about is a good option for handling some power. The springs should fit right on, a little finess will get you a driveline setup that will work, and the axle is stronger than a Dana44. Gear ratios are going to be the problem though. The info I have says that 4.10 is the lowest (numerically speaking) ratio that Isuzu put into anything. You'd have to just put bigger tires on I guess. Too bad Isuzu never put these things in a turbo impulse, with a 2.6L motor.


One point that comes to mind though, is what RPM are you actually getting on the motor at 60MPH? If the speedo is your only problem, find a different speedo gear or some kind of ratio adapter. I'd say it is more important to have the motor revving in the right range that correcting your speedo reading.

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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

I'm turning to many revs... At cruise (70 mph 'round here) it's near screaming, and I'd really like to slow that down. Installing a tach is also on the list, along with Oil Pressure , Oil Temp and actual temp gauges. Trying to decide which oil would be better to watch, engine or tranny...

I have a long list of minor projects ahead of me, for as soon as I get the $$$ to do some.

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1978 shortbed fleetside, th350, Fireball 231 Even Fire V6, Edelbrock 500CFM Performer with Edelbrock intake. Workin' Truck.

Yep, not just the speedo, I have the same problem with mine, with the exact same setup, my speedo reads about 100 when I am doing 70 and sounds like the truck is going to blow up! Been so long since I drove it, I forgot what the RPMs were.

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Click on C.M. logo to go to my webpage


RIP R.J.B.

So, I found this item on ebay...

It's the rear end from an '87 3.9L Turbo-Diesel 5-speed... 5-lug hubs.

Would I be able to unbolt and remove the diff and pop it into my axle, or is that too much to hope for?

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1978 shortbed fleetside, th350, Fireball 231 Even Fire V6, Edelbrock 500CFM Performer with Edelbrock intake. Workin' Truck.

That one on ebay is from a large truck, think like flat bed car hauler or box van. 5 lug bud wheels, set up for big duals. Not to say you could not make it fit, but it isn't going to bolt on.

Sounds like the 3.42 gears are the right cure then, that or an axle swap that gets you into the right range. My math is probably off, but I think that comes out to something like 2.87, but I could be wrong. It is late and I'm not quite firing on all brain cells.

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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