Looking at doing some more upgrades to the truck this summer I'm thinking about going to 33x12.5x15 baja claw ttc tires and changing to 4.56 gears and eaton tru track in the rear. (current gear 3.55) The truck is a M5R2 trans with fox body HO motor.
The truck rarely sees the highway and lives 90% of its life under 50mph. Will the lower gear help ease the stress on the trans? How noticeable will the change be? Any suggestions will be appreciated.

 

4.56 gears seem like a reasonable choice with not much highway.

I've gotta ask about the Baja Claws and True Trac. I wouldn't think the Claws would be a very good choice unless some significant 'wheeling was planned. And if 'wheeling is the goal I'd definitely go with a locker over a True Trac

 

I have a set of "on road tires" as well that I can use for planned highway trips. I originally wanted to go with the detroit locker but i have heard not so great things about its road manners. Does anyone have any experience with one of these on the road? the truck will probably be 20% trail %40 farm/gravel and %40 pavement

 

I have one in my 88 and I haven't had any problems with it on dry road or wet from rain but I haven't driven the truck after a snow (yet probably this weekend I will be).


It does really good driving around the yard and on the dirt road/trails. What I don't like is if I hit to loose of gravel it breaks loose and gets a slight wheel hop like.


I do 50 mph everyday with it and never have one issue and so far haven't found one time where I felt I needed 4wheel drive with it versus stock LS (had the stock LS in a similar truck I drove for a while).
Trav

 

Will the M5R2 like the lower gears? I know its not the stoutest transmission.

 

Should make it easier on the transmission since the gears will give it a better mechanical advantage to get the load moving

 

Sounds like a good plan to me.

 

I had a Detroit in the rear of a J**p CJ5 for ~10 years / 20K miles, a LockRight in the rear of an F-150 for 9 years / 120K miles, and a Detroit in the rear of a '71 Bronco for 7 years / 40K miles.

On dry pavement they aren't too bad. Starting around a corner they only drive the inside tire, so it's easy to break that tire loose, which is a little annoying, but you learn to drive with a lighter foot and it's OK. Although I will say that it's worse when pulling a trailer, and I would not recommend an automatic locker for a vehicle that will often pull heavier trailers.

On ice and snow it can be pretty easy to break one tire loose (especially when starting in a corner), and then when it catches up with the other tire it can "hammer" that loose too, which can result in a spinout. But that's something you can get used to as well. I drove that F-150 through 9 Minnesota winters and never had a problem. In fact, in my experience it's easier to keep a locker-equipped vehicle from spinning out than one with a (not worn out) clutch-type limited slip.

You do get some noticeable "clunking" and torque steer as you get on and off the throttle. That's more significant in smaller vehicles and with manual transmissions. It was a little annoying in my CJ5 (manual trans), it's noticeable but not usually annoying in my Bronco (manual trans), it was almost completely unnoticeable in my F-150 (auto trans).

Automatic lockers are a little quirky, and if you will be letting others (especially your teenage sons if you're in my demographic) drive the truck you might not want a locker. But if you'll be the only driver, I'm sure you'll be able to get used to it and will be able to drive it safely (even if you are someone's teenaged son!). And if you value the performance off road enough, you won't mind the little that it "costs" you on road.

 

My opinion is that 4.56 might be a bit low for a 33" tire. I have 4.56 and run a 36" tire which seems to be just right for that tire size.

 

I been running 33/12.5s with 3:55 for years. We live in BC tonnes of hills, daily driver. We also tow a horse trailer and don't even notice the difference from a stock size. (manual) only a 302.

If you have the time and funds i'd say go nuts, sets you up for bigger tires down the road

 

CaptJack what motor you got? If it's the 5.0 then 4.30-4.56 is the right choice for performance and towing applications IMO, if you got a 5.8 it won't need as much gear and if it's the I6 its also a bit of a mismatch because the I6 makes all it's power at low rpms.

 

you get used to the Detroit. i have one in the back of my xj, just do not get off the throttle mid high speed corner. i wouldn't want a trutrack. no warranty for off-road use. no warranty when using over 33" tires. why spend all the money to have a fancy open diff with no warranty.
here is a good watch if you got the 20 minutes.

 

That video is pretty good. He's a little sloppy with terms, calling the side gears "spider gears", saying an open diff sends all the torque to the tire with no traction (it sends equal torque to both tires), saying an automatic locker has no clutches (it has dog clutches, which don't wear out, but they are clutches). But none of that really changes any understanding.

He does say that automatic lockers can make you suddenly change lanes as they lock and unlock. That's true in a front axle, but really not in a rear. You'll get some torque steer, but even in a CJ5 it's not hard to correct for it. In a full size pickup it's hardly noticeable.

He also says you get a lot of tire chirping as automatic lockers lock and unlock in corners. That can be true, but only if you are getting on and off the throttle hard. Automatic lockers work based on relative velocity, not torque or power. So they unlock when one tire wants to overrun (the outside tire in a corner) and they lock when the tires return to the same speed. This happens when you return to a straight line, or when you spin the inside tire by applying too much power. But the chirp doesn't happen when the locker locks or unlocks, it happens when you give it too much gas. That's why it's not that hard to get used to, you learn to not give it too much gas (or back off too abruptly with a manual trans).

He does say one thing I agree with 100%: a selectable locker is the only choice in a front axle.

 

It's a mustang 5.0 ho 90s vintage in a 90 speed density f150 m5r2 4x4 truck. Only mods to the motor are long tube headers. The motor does make it power a little higher in the rpm range but it is much better than the original 5.0 that came in the truck. Lie stated in the original post it will not see much highway driving. From what you guys are telling me a 4.56 gear with a Detroit locker would be a pretty mean off road setup?

 

Yes, that will be a great combo. If you do a lot of city driving you may get start to tire of having to shift so often, but I think it's worth it. You can always skip gears, say 1/3/5 (or even just starting in 2nd..) to save some of that shifting.