My 2wd, supercab truck has a 351W and 3.55 gears and A4OD, which means it's only rated up to 6300lbs, according to the owner's manual. So far I've only towed up to about 4000lbs (a '93 Taurus on a tow dolly), and while it did the deed, the truck could not maintain speed on any kind of grade in OD, and didn't want to go much past 65 in third without really goosing it. I'd like to be able to comfortably tow a ~4000lb car on a 1200lb car carrier trailer, and while the truck can do it as-is, I'm considering an upgrade.

I had been thinking of putting an Eaton Truetrac 915A550 limited slip diff into the truck, for increased traction on loose surfaces. I figure if I'm going to get that put in, I could swap to 4.10 gears at the same time, which *should* increase the factory rated towing capacity to 7800lbs and make the work much easier on the truck, while sacrificing a bit of fuel economy. Any opinions on this plan? Thanks.

 

The 4.10 gears will help, as will the limited slip. And just slow down, you're towing, it's not a race. Just leave twenty minutes earlier. Otherwise you'll need a newer diesel. But sounds like a nice truck you have there.

 

Yeah I try to take my time when towing, I just don't like to hold up traffic too much on the Interstate. I'm quite happy doing 60mph the whole trip if traffic is light.


The limited slip is mostly for dirt and gravel driveways. I've had trouble making it up a particularly steep gravel driveway with an empty bed before, resulting in a one wheel peel.


And thank you for the compliment, it really is a nice truck with an absolutely solid body (came from the south). I park it from december to march so as to keep the road salt off it.

 

solid plan.

 

Next time take it out of OD, it will cost you NOTHING and it will be like having 4.10s

Also, it is NOT a wise decision to go over 65 while towing

 

I do leave off overdrive now unless I'm on a long, level grade of highway where it won't constantly hunt between 3rd and OD.

 

So which is it?


get your story straight

 

The first time I towed, I left overdrive on, which showed me that it could not maintain speed in OD on any uphill grade. Realizing that hunting between 3rd and OD is bad for the transmission, from that point on I have turned OD off when towing unless I'm on a long level stretch of highway.

 

I had a '95 F-150 with a 351, 3.55 gears and an E4OD trans (by the way, that's probably what you have. There's no such thing as an A4OD. There is an AOD, but it's lighter duty and probably wouldn't be in an F-250HD). Anyway, I felt like that towed 3500 lbs OK (with the truck also maxed out, including a slide-in camper). It could have used lower gears, but as Brad said, leaving the trans in 3rd made it pretty good.

You won't be able to hold speed on steep hills though, it is just a 351. Expect to slow down there.

If you are putting a TrueTrac in it is a good time to regear. If it were me, I'd end up using the truck empty a lot more than towing, so I'd stick with the 3.55s. But if the truck will do mostly towing 4.10s wouldn't be a bad idea.

 

Yeah sorry, I meant E4OD. I had a '92 Crown Vic with a AOD, got a little dyslexic there for a moment.

The truck is just fine by itself, even with a ton of weight in the back. Only gets sluggish when towing over 3k.


Does anyone have experience with the TrueTrac diff? Good, bad, ugly? I like it on paper because it's clutchless so there's no clutch packs to replace on a periodic basis.

 

No personal experience with them, but everyone I've heard has pretty much the same things to say about them: love them where an open diff or limited slip is best, not so great when you really need a locker.

The odd thing about the Truetrac is that it gives something like 3.5 times as much torque to the tire with traction as it gives to the tire without traction. That works great as long as both tires have some traction, but if one tire is in the air it gets zero torque and the other tire gets 3.5 x 0 = 0 torque and you sit there with one tire spinning.

That sounds like a horrible problem, but it isn't really. How often are you in a situation where one tire gets really good traction and the other gets none? Typically both tires will get at least some traction. If you are lifting tires in the air a lot, then you really ought to get a locker. Otherwise a Truetrac will work well. (and even if you do end up spinning one tire, you can give it a few clicks of emergency brake and trick it into giving more torque to the other tire, the Truetrac is the only diff this trick really works with).

 

Yeah, I've read about the torsen diff "apply brake" trick to get some power to the ground with one wheel completely in the air. Pretty cool. I don't really do off roading with the truck, the worst it sees is gravel, dirt, maybe a bit of mud on a dirt road.

 

4.10s would definitely help, but as would doing the "six-liter" tuneup and maybe putting some headers on it.

 

Trutrac is perfect for what you want it for, they make a huge difference to a 2wd truck. And if you are doing it then certainly upgrade to 4.10's for the rear. Most people wonder why they didn't come from the factory that way.

 

Headers are part of the plan anyway, as one of the exhaust manifolds is slightly warped and causing a minor (but annoying) leak.