hey guys, would an 81 long bed 4x4 pickup with a 22r, 5 speed, rears in front, 3 inch spring lift in rear get better gas mileage with stock 3.90 gears or with 4.10's front and rear, locked in the rear the tires are either 30x9.5x15 or 31x10.5x15 i don't know if this a stupid question but i sure would like an answer, anyone here know the difference of gas mileage whether the 3.90's are better or worst than the 4.10's locked in rear free up front at gas mileage? sorry if this is repetative, im trying to be as clear as i can be.. also what kind of drawbacks are there for having a welded locked rear diff for daily driving? anyone here rather stay with 3.90 or go to 4.10 its a choice im thinking of doing let me know what you think..

 

anyone??

 

I left the gears stock and was running 31's on my '81. I thought it was fine and actually got the best milage with that setup. My engine was upgraded as well so if you have a worn out stock 22r you may need to re-gear to be able to pull a hill. How's the engine? What are you planning to do with the truck? Is it your DD? If it's something you're trailering to the trail, go ahead and weld the diff, if not, DON'T. Will answer what i can. Got my truck stock and over 10 yrs or so slowly worked it up to 35's, detroit rear open front, hopped up 22r with dual sidedraft webbers, ect.

 

Hey, thanks for the info Bingle, and yes upon further research i found on other forums it seems that its great for the trails, i will need it to be a dd so i will be keeping my axles at stock 3.90's then.. i dont plan on ever going bigger than 33's realistically im going to roll in 31's the gas prices arent helping my choice at all..

 

33's you'll wanna regear. 31's, webber carb (especially a 32/36 on an Offy dual plane manifold), header, and cam and you'll be fine in my oppinion.

 

31.10.50s/ 4.56,s gears with a detroit locker out back and i get a tick under 20mpg and dont down shift on hills.. changing from the 4.10s to 4.56s is one of the best things i have done to my truck.

 

A limited-slip diff on a daily driver is already a double-edged sword - more likely to get you going than an open, but a good bit harder to control once you *are* going. That's a differential that locks only sometimes. And you want a diff that's locked all the time? Bad idea in the dry (tire wear, skidding in turns), bad idea in the wet (unless you can and want to be drifting all the time).

 

Looks like all of you guys have reading to do.
Auto lockers arent always locked. only when torque is applied to the wheels.
and 4.88s for 33s. and 4.56s for 31s.
But a welded rear end with wear your tires like mentioned.
And with a 22r you should regear any way.
A locker shouldnt change your mpg, except for when you change your driving style.

I didnt know of 3.90s coming in 4x4 pick-ups? but that small of a jump wont really matter. if your gonna gear at least go 4.56s.

 

My comment was in regards to a welded rear end. I know that auto-lockers aren't always-lockers

3.90 was 81 only, apparently, but that seems to be the most common 1st-gen year. Diesels and some 1-tons had 3.90's as well, though I don't know if either are the standard Toyota 8".

4wd ratios according to car-part's database:
79-80: 4.38
81: 3.90
82-85: 4.10
86-88: 4.10, 4.38
89-92: 4.10, 4.56
93-95: 4.10, 4.30, 4.56, 4.88

 

Gedrven have you driven a welded rear with a 22r? I have a hard time believing he'd be drifting in the wet or skidding(unless by skidding you're just talking about the inside tire chirping) in the dry unless he actually tried to. I have 5.29's, welded, on 33's, with a fairly powerful(for a 22r) modded engine and I've never had the rearend slide out unless I meant it to. I'm almost always totally empty in the rear, too, cause it's only my trail rig.

Now, to Lingura, I'm not suggesting you should weld the rear of your daily driver, it does increase your tire wear and is just usually not necessary. An Aussie or other auto locker, I couldn't speak for in the rear, only have experience with it in the front of my '83. As for the gears, my suggestion would be 4.56's for the 31's unless you live in some fairy lala land where you get to drive downhill with the wind at your back at all times.

 

My set up is Stock 4.38 weld rear open front. I have been driving mine daily with it weld. Its not bad at all IMO. I also have 35's. I get 15
MPG Hwy with a 20R and a L43 4 speed.

 

No, just speaking from experience with other chassis (cars). Those tended to have a lot less rubber between the locked axles and the ground than your 33's do

 

I welded the rear spiders on my Dodge pickup, and although there was a learning curve, it was very controllable. It WILL eat tires up, no matter what make/model/size of truck or tires you have. It was my daily driver, and I drove it pretty hard...which is why I wasn't surprised when I eventually grenaded the rear carrier. I was doing a lot of city driving, though, and those tight corners and pavement really put stress on welded diffs.