picking up a 2000 f350 7.3l crew cab short bed 4x4 next week.and im looking to lock the rear and gear it.what would you guys suggest as far as gears go and lockers. i was thinking 4:56 or 4:88 and an eaton posi but im not positive on what the best for these diffs are.i tow a 36' triple axle toyhauler that weighs about 15k.i will be getting intake,straight pipe and a livewire tune so that will help out some.i will be running the donahoe 7" mid travel lift and on 37s on 20" or 18" wheels.and also if you could recommend a place to order up the gears for a good deal that'd be great.i will be installing these myself.thanks in advance

 

If you plan on running a 4.88 in that truck, don't ever plan on reaching 70 MPH. As for the rear end, are you looking for a locker or a limited slip? There is a difference. And the mods, you can do better. An intake won't do much to a 7.3, look into doing something with the boost tubes and intercooler instead.

 

If you're really towing 15,000lbs with 37" tires, you're going to want all the gear you can get. 4.88 ring and pinions may not be overkill even for your diesel considering many trucks come with 32" tires stock and what, 3.73 gears? I don't have any transmission ratios in front of me right now so it's hard to say what RPMs you'd be turing.

As far as the differential, Pinky is right. There is a huge difference between a locking differential and a limited slip or "posi" as GM dubbed them years ago. Again, seeing as you'll tow you might be better off with a limited slip such as the Eaton you mentioned or the Tru-Trac. If it were me, the TruTrac would get the nod simply because of it's gear-driven torque baising nature. It won't gradually wear out over time like the OEM Traction Loc or the aftermatket Eaton or even Auburn limited slips.

I had an Auburn, for example, in a Ford pickup and hated it because I really needed a true locking differential. It would spin both wheels in the sand and mud most times, but the minute the suspension articulated or both wheels were not on the same kind of surface it would only spin the low traction tire. Applying parking brake and all the other "tricks" were futile. I wasted $600+...

The automatic locking differentials will provide a lot more traction because they have a system that mechanically locks the side gears of the differential together and will not let a tire stop turning in tough off road conditions like a limited slip will. The drawback is, of course, they could introduce some ratcheting noise or barking of tires on road in tight turns if you step on the accelerator too hard. Towing could magnify that occurance since it takes so much more engine power to get your rig moving around tight areas.


Whatever you do, make sure you do your reasearch. Axle work with gears and differentials is expensive and you don't want to drop $3000 to figure out it's not exactly what you had in mind.

 

I didn't like the eaton LSD in my truck. Clutches didn't hold up, they chattered, the specs said to use 80w90 dino oil which I thought was too light and I was never able to get a good answer as to why such light oil. The clutches ended up frying, probably because of the synthetic gear lube I used, but none the less there are better options that use the right gear lube IMO. If you want a limited slip, go with a true trac, if you want a locker there are choices there, but determine your needs adequately first.

 

Depending on the transmission in your new truck, the "Transmission High Gear Ratio" is as follows:

5 Speed Manual - .76
6 Speed Manual - .72
Automatic - .71

RPM Calculator

3.73 Gears - Using the Gear Calculator link above, 31" tires will generate the following RPM's at 65 MPH:

5 Speed Manual - 1,999 RPM's
6 Speed Manual - 1,874 RPM's
Automatic - 1,868 RPM's

Note: I recommend driving the new truck with your TT to determine if you are happy with the pulling power with the 3.73 gears and 31" tires.


4.56 Gears - Using the Gear Calculator link above, 37" tires will generate the following RPM's at 65 MPH:

5 Speed Manual - 2,048 RPM's
6 Speed Manual - 1,940 RPM's
Automatic - 1,913 RPM's

Note: 4.56 gears will keep you close to stock RPM's with the 37" tires.


4.88 Gears - Using the Gear Calculator link above, 37" tires will generate the following RPM's at 65 MPH:

5 Speed Manual - 2,191 RPM's
6 Speed Manual - 2,076 RPM's
Automatic - 2,047 RPM's

Note: 4.88 gears will raise the RPM's approximately 200 RPM's with the 37" tires.


As for sources for gears and differentials, here are two links that have been recommended by other FTE members:

Early Bronco Restoration Full Size Bronco Restoration Classic Ford Bronco Parts For Sale

Randy's Ring & Pinion. The Differential Experts. Auto Parts & Services.

 

wow thanks for the quick responses everyone.it is a stock auto trans.as far as the limited slip/posi goes.i had posi in my lowered 6liter gm truck and i know in the rain it was sketch and it chirped tires around corners.i go to the mud and sand alot and im not ALWAYS towing.i usually go out about 20 or so times a year on average.so i'd prefer a locker since i hate when you have articulation and only one tire spinning.with this all being said,whats your opinions now?

 

My Auburn Limited Slip was very similar- I'd chirp the tires around a hard corner and get sideways in a hurry in the ice. Yet when the conditions got tough off road, it would slip like mad. The correct lubricant was used, and when I got sick of all the peg-leggin' I even tried a complete drain and refill WITHOUT and friction modifier. It still didn't help.

As far as I was concerned, it had almost all of the on-road drawbacks of a locking differential with none of the off-road traction benefits.

The next thing to determine if now that you're looking at locking differentials is your budget. The selectable locker (ARB) is the best of both worlds- open or spool; you decide. But it's the most expensive and most complex. Be sure to budget for the necessary air compressor to activate the unit and the air lines and small pressure tank. I'm considering this locking differential and it looks like it'll cost $1200-$1500 just for the equipment alone.

The only other choce I think is available for our Super Dutys is the venerable Detroit Locker. It's considered an automatic locking differential. It uses dog clutches inside the differential that are speed-sensitive. In a turn, the unit is able to allow the outside wheel in a turn to drive faster than the inside. It "ratchets" (I think this is the correct way to describe it), which is sometimes audible in low speed manuvers on the road. Off road, as long as power is even moderate applied, it's going to drive both wheels equally giving maximum traction. I think the Detroit Locker runs $600-$700.

These are the only choices available to Super Duty owners for the rear axle as far as I know.


The front opens up a whole bunch of options because of the widely used Dana 60. Everything is pretty much available: ARB, Detroit, E-Locker, OX-Locker, etc... Your 2000 F250 MAY HAVE A DANA 50, so double-check before ordering any parts.

 

Hey Gr$$n$ I know your a so cal resident. Give a call over to Hoopers Rear End exchange in Pacoima. They have been around forever and have good pricing for the work. Call them and they can give you a quote over the phone.

 

ya ive always loved the arb and ill be running rear helper bags with a comp n tank anyways but ill have to check on that.i'd rather just do the detroit personally.

ya i know of hoopers.500 per diff for gear swap but lockers are more.if i wasnt doing this out of my garage i'd go to them.they are a very good company i stand by you on that one.but thanks anyways

 

I like the Tru Trac myself. Had one installed to be used for better rain and snow traction when I snow plow. Works absolutely fantastic. You have to have a certain degree of pre-load but when you do, it helps tremendously. Rain traction works great too.

 

I am still confused..lol. I have an 08 F350 4x4 with 4:10's and an open diff. I want to get better traction in the snow. I have read that the Detroit True Trac is good for what I want to do, is that true? it should work like a limited slip just without the clutches right?

 

Yes and Yes... See the link below for details of the various Eaton differentials.

Differentials

 

Thanks, I have been looking at them for a while. Just want to make sure it is going to do what i want. Sounds like it should. I will order one next week, should be an easy swap out.

 

Hold the boat dude. It's more of a Kinda Sorta and Yes. Lockers aren't the best idea all the time because of ice traction and general dry pavement drivability. I'd hate to not throw my .02c in and have someone fishtailing all over a highway because they put in a locker and didn't know what to expect.

Myf350sd, there are a lot of threads about lockers vs. LS units and snow/ice in the forum. If you can't find one, start a new one and we can hash out the details again.


Edit: I saw he said Detroit True Trac and not Locker, which is actually the right call IMO. I'm just used to seeing Detroit and automatically thinking locker, but still, he might want to talk more.

 

I too took a double look when I read Detroit TrueTrac... I would love to see Eaton make the E-Locker for the Sterling rear axle. I sent a request to Eaton for this new application but only received the standard "Give us a call" response...