Best gas mileage towing drivetrain for my F250 4x4?

ripsnorter · Post by **ripsnorter** » October 2, 2009, 11:12 pm

Okay, I'm getting a bit serious about finally tearing into my '63 F250 Flareside. I need some advice (since I'm not just thinking theoretical anymore) on what I should do for a drivetrain.

Right now it's stock with no drivetrain at all. I have an '81-2 F250 4x4 that I plan on ripping the 4x4 (probably use the frame and all) out of for the '63.

Mostly though I want to figure out what I should look for in donor drivetrains. I'm going to use it mainly for pulling a carhauler trailer, (probably 10,000 max gross when loaded) but it would be nice to have something that would get as good of mileage as possible.

Incidently, are there any transmissions that would stand up to being run in overdrive while pulling a load like that?

I have a few 460s, so I'm pretty decided on that for a motor. I don't want a diesel. What should I look for in a transmission? I'm thinking I'd rather have a manual than automatic, but I'm not set on that. I have access to a 90s diesel 5-speed, a ZF I think it is. I know it won't bolt straight up to the 460 without an adapter plate, but is there a better heavy duty manual out there? I'd really like something that will drop 1000 RPMs in overdrive. What's the best I can do, and will I need to use something like a Gear Vendors to get it? What should I start looking for?

I've got a few months before I start on this project, so I'd like to use the time before then to try and track down some good used parts, especially if I need something like a Gear Vendors. Although Gear Vendors won't actually increase my overdrive I don't think, is there anything out there like it that will?

Thanks guys for any help, I've missed hanging out here

ICEMAN6166 · Post by **ICEMAN6166** » October 2, 2009, 11:18 pm

wb Rip

friend of mine has the id auto trans in his 4x4 says it sucks, its behind a diesel but i have driven it and agree with him.

i would go with the zf or another 5 speed manual.

Hoofbeat Racer · Post by **Hoofbeat Racer** » October 2, 2009, 11:34 pm

welcome back Rip, it's good to see you back.

Wait for Tom (36truck) to chime in. I believe he is going to run an NP4500 behind his 460 in a 79 4x4. They are plentiful and should work for you as well

ripsnorter · Post by **ripsnorter** » October 3, 2009, 12:38 am

The nice part about that ZF is it's such a heavy duty tranny with an overdrive. I'm not sure what the ratios are in it though, or how much it will drop the RPMs in overdrive.

Anyone have any experience with towing in overdrive on those? I know when I borrowed my dad's AOD I never dared have it in OD while I towed unless I was empty and going downhill.

I'm off to look up the ratio specs on NP4500s and ZFs.

robert porterfield · Post by **robert porterfield** » October 3, 2009, 12:49 am

wb rip....go w/ zf, use the gas model, diesel versions have much tighter ratio's in them....looked into this myself, at some point will try it....hope this helps...

ripsnorter · Post by **ripsnorter** » October 3, 2009, 1:28 am

after a little bit of research...

NP4500 is a 4 speed non-overdrive isnt it?

and it seems that Gear Vendors will indeed add an over to the overdrive, making it double-overdrive. According to the specs on their site :

http://www.gearvendors.com/fdrive.html

The ZF stock has a 0.76 overdrive ratio, and with Gear Vendors added it will bring it down to 0.59 in double overdrive.(great!)

Obviously I wouldn't want to run double-overdrive when towing, but I'm wondering how 4th+over would run when towing since they really tout the strength of their planetaries.

Anyone have any experience with Gear Vendors? I'm seeing them on Ebay and craigslist for around $700 to $1000 used, plus adapters.

oldtrucks · Post by **oldtrucks** » October 3, 2009, 2:42 am

ripsnorter

Welcome back

You haven't said anything about the final drive gear ratio. To use the double overdrive you are talking about you will need a ratio of about 4.56 at least. I run a 429 in my truck 4 speed and 4.11 gear ratio. the tires are 265 75R 16.
The tack is running about 3500 at 75 MPH loaded or empty. My fuel economy, if you can call it that, is 8 to 10 MPG loaded 12 to 14 empty. The truck is 7200 LBS empty trailer is about 2200 lbs empty so when I am hauling a standard car my gross is somewhere around 16,000 LBS. I don't have an overdrive and if I did it would be useless with the rear gearing I have, even empty I would have to shift out of overdrive to pull any hill.

Having said all of that my opinion is that I need at least a 5 speed trans without overdrive and a 6 speed with overdrive and a 4.36 gear to get to the point that I might get above 16 MPG empty. Loaded I should stay above 10 with the 5 speed and I might get lucky and get 12 or so with a 6 speed. The reason I want so many gears is I want to keep my engine in its optimal power band at all times. The biggest killer of fuel mileage in a working engine is lugging it. The 3rd to 4th gear RPM split in most 4 speeds we use is about 800 RPM, thats too much for pulling hills, which I do a lot of here where I live. The cost to get the trans I would like the rear gearing I would like is more than I could justify. My truck is a 4/4 so I would need an additional set of gears for the front axle.

This is my situation so I hope my ramblings have given you something to consider.

ripsnorter · Post by **ripsnorter** » October 3, 2009, 5:26 am

The trailer itself is a tandem axle 18 footer carhauler, I think the weight of 2200 on it sounds about right too. The normal heavy load we have is probably in the 8,000lb range, plus trailer, so 10,000+ gross on the trailer on a heavy run. The heaviest I've ever seen it have was probably 15,000 to 16,000 gross. (overloaded on a short run there, we didn't calculate it out til later)

I grew up pulling it with various trucks of my dads, all of them F250 4x4s running 460s with 4.10 gears and autos.

At 70-75mph he's spinning 3500RPM like you said, which just seems disgustingly over-revved. I don't see any reason why if it's just the truck itself, empty, it shouldn't be idling down the freeway at about 2100 RPMs. Climbing hills or loaded down is obviously a different story. I've never run out of power pulling that trailer with the 460 though.

I like the idea of a 5 speed with a gear vendors behind that, as that would give me an over/under on each gear, which would further help me out when climbing etc. About the best I would hope for when towing a loaded trailer would be 4th with the Gear Vendors over, if that'll even work, and obviously not while climbing hills. Especially with a manual tranny, each hill/drive kind of dictates it's own RPM/load feel and range.

The short version of all of the above paragraphs is that I want to be able to keep it in the powerband with a lot of gears when needed, but able to drop the RPMs down when I don't need the power.

The '63 has 4.56's in it right now, but I'll probably swap the entire chassis out of the '81, which has 4.10/11 in it I believe.

36truck · Post by **36truck** » October 3, 2009, 10:02 pm

The ZF5spd comes in many bellhousing bolt patterns. 351W,460,diesel& mod motor.They are a good trans for towing with the granny first to get you going with the heavy load & OD for the highway. I would try it out before you get the gearvendors OD & see how it works.

ripsnorter · Post by **ripsnorter** » October 4, 2009, 2:28 am

Forums are having problems still? Having a tough time getting in tonight.

Anyway..

I've pretty much decided on the ZF, (I think Hoofbeat meant the NV4500 not NP? which is a 5speed overdrive) The one I have is in an early 90s F250 diesel minus the engine, so it would definately be a diesel tranny. I'm trying to find out if there are any adapters out there for it or if I'll have to have one made. I'd hate to waste the one I have and buy a gas instead if theres an adapter for what I have.

I think the ZF I have is the S42, which is 420ft-lbs torque, and supposed to be a little smoother shifting than the S47 (470ft-lbs)

Most likely I'll just do a complete frame swap from the 90s diesel to the '66. I'm sure it will take some modifications to do, but seems to be the simplest way to achieve my goal. I still need to pick out a 460 though, I'll probably end up rebuilding one of the ones out of the '69 Lincoln Mark IIIs I scrapped, unless I just end up buying one off Craigslist that's already been rebuilt. I hate doing that though and not knowing what's in it.

oldtrucks · Post by **oldtrucks** » October 4, 2009, 5:13 pm

I agree with you on buying someones rebuild unless it is from a recognised builder with a warranty. Would rather build it myself that way I know what is in it and the quality of the machine work.

36truck · Post by **36truck** » October 4, 2009, 8:17 pm

Check out your bolt pattern on the diesel & the 460. Some of the early diesel's had the same bolt pattern. Don't know of any adapters.