Rear axle

So I want a economical truck that is capable offroad and on the highway. I located a 3.3L V6 in a minivan and a jeep wrangler with a 3.8, i want to mix the 2 together. It has a single overdrive NSG370 transmission with a high first and a similar to the KM145 6th gear. Could I use the factory axles or do I need to swap them? Can i use a lower gear ratio, or is there aftermarket gear ratios or different gears I can use? I would like to cruise below 2000 rpm if I can, hopefully below 1750 (goal is 1700 or something close). Thanks!

I swapped out my open 3.88 for a 4.22 LSD
in my case i put a complete 2nd gen diff in a first gen truck, there was no issues.
What tyre size are you running as this makes a difference, (my truck went from 14's to the biggest 15s i could fit and not foul the front arches)

you need to plug your final gear ratio (probably overdirve?) current diff ratio, and tyre size into a rpm calculator and then go from there


Theres a few different options depending on what you end up with, the trucks had a few different diff ratios, you have the option to swap in a diff from a few other vechicles or to buy the diff gears seperately



Power wise
my truck has no issues with the open diff or the LSD with 170hp.
The guy i got my diff off had his v6 twin turbo'ed and if i recall correctly the open diffs last a bit longer when you rag on them, theres a pin that shears off and wrecks them. but if you drive sensibly you can use the original no worries. If the one thats in there is of a suitable ratio even better as its free

I did the calculator, 235/75/15 tires 29.8" tall give or take some for M/T tire and 'tire squat' or sag. I need a 3.73 or lower. I dont know much about differentials so if you could explain the different types and how they work that would be much appreciated.

A 3.73 turns up 2000 rpm at 55 mph. So anything 3.73 or lower would work nicely. I like the idea of a 3.54 or a 3
23 or maybe even a 3.08. But I dont want it to be so low that it becomes underwhelming. So I would like to keep it at 3.50 ish.

The 3.3L with a 3.8 crank and cam will be pushing close to 200-220 hp and 240-250 tq before the turbo. It weighs the same as a G54B. I can use a jeep ECU and be good to go. I wont be gunning it all the time, but every once in a while I might just enjoy my truck.

Check your diff to see what you have, you might have soemthing suitable. should be on your build plate on the truck

2nd gen 2wd autos had a 3.55 ratio, just take the whole rear end its less messing about than changing the centre out.

open diff, all the power goes to the tyre with the least traction

LSD Most of the power will go to the tyre with the least traction, but some will be forced to go to the other as well = 2 tyre burnouts (and good for soft ground etc where its easy to get stuck)

Ok I see, so a LSD is better. Much thanks!!! Now the rear end on a 2wd is smaller (to my knowledge) so that's a downside, but a 3.55 isnt a bad gear. I will try to find one. The calculator said 1900 RPM at 55 and 2600 at 75. Not too bad but could be better. But now my front end ratio is a 3.91 and my rear end is a 3.55, so what do I do now? I would HAVE to change the center out then, so may as well keep the 8" rear and adapt the 3.55 gears to it.

Does a 2wd have a LSD???

2wd can have LSD

I didnt realise you had/were keeping a 4wd truck. you can swap the centres into the front i believe. theres some posts about it on here but i havent looked into it much

if you have a 4wd you may as well use lockers front and rear, theres some posts about that here too

I dont like lockers that much, I want a smooth engagement not a snap crackle and a pop like a old man falling down a flight of steps. A locker would put stress on the drivetrain lol.

A POWERRAM50 is a 4x4 a RAM50 is a 2x4, POWER stands for 4x4. Unless yall cant see that my vehicle is a 1987 PR50. In which case it is. I see you have a 1981 Mitsu L200.

What's the lowes gear I could find between all the mitsu cars that could be compatible, like montero/raider, arrow, conquest/starion, d50, mm, etc.

yeah our L200s didnt have the "power" badge, we just have L200 or 4wd L200s
you wouldnt drive on the lockers all the time, turn them on and off when needed i.e in the mud. plenty of new items you can get, could even track tdown an air locker for the rear

i think starions had the lowest, the gearsets are a bit thin on the ground but do come up if you search

i found an aftermarket set of 3.23's, but I thought about 305/75/15 tires and a bit of lift (maybe 2") so a 3.23 might be a bit underwhelming then. I think with a 31 or a 32 a 3.55 would work great, but a 3.23 in 5th says 1900 and 6th is 1600, a bit low for my taste. the nsg 370 has some really odd gear ratios, a really high first and a fifth gear direct drive as well as a 2.61 second 1.72 third and a 1.25 fourth. now I think there is a gear vendors overdrive for the nsg 370 and that could help alot ; I could run a 3.91 or higher and have the rpm's I want. now there is an adapter kit for a tremec tr 4045 5 speed to bolt to the 3.3 / 3.8 and I might just do that but it takes alot of $$$$$ that I don't feel like spending now. it has a 6.16 first (great for offroad) 3.11 second (takeoff gear for every day driving) 1.71 third direct fourth and a .76 fifth. because it has such high starting gears a 3.55 is almost necessary, and the twin turbo power can hold up with the steep drops that come with it. but a .76 allows for 1725 rpm with the 28.9 tires and 3.55 gear. so I think I will do a center swap on both and try to find a montero/conquest/ram50 to get it from as long as the lsd isn't burnt to shit.

if you go with the 3.54 rear gears, get a center section from a starquest rear - 3.54 and lsd, and drops right into front housing.

what about the rear section. same story?

Not quite as easy. The front and rear differentials are different size. The rears are an 8.5 inch ring gear with the front a 7.5, if I remember correctly. The differential out of any 4-cylinder D50/MM will fit, as will the ones out of the early Monteros/Raiders. The V6 trucks may also use the same size, but I'm not sure, they may have used a slightly larger one. If you wanted 3.55 gears, assuming you can find a truck with those in it, they should swap over no problem in the rear.