What transmission would you choose????

Vader's Fury · Jun 5, 2012

I am working on collecting parts to build a purpose built tow rig. I have the chassis and engine figured out but am trying to decide on which trans to use. While money is a consideration, I want to build something that will last and that will suit my needs for years to come.

The chassis is a International 4600 low pro and I want to stay with my 7.3 dinosaur.

So basically I am asking, If you could use any transmission for your tow rig, which one would you pick and why?

And this discussion does not have to be limited to just ford transmissions.

Vader's Fury · Jun 5, 2012

Anyone?

Beans71086 · Jun 5, 2012

6+ spd spicer, but I like to shift gears. As far as a auto goes probably an Allison 2000 if you could find the wiring to make it work with your 7.3.

Jason · Jun 5, 2012

Manual. I love those little lo-pro 4700's, id like to find a 7.3 5 speed with air ride.

Anyhow...im not sure what the ratio in them is but i can imagine its steep to comoensate for low hp. For having a decent cruise speed and mpg when towing, id try to find a lighter duty 13spd. Ive seen a few put into dodges, and chevy's, so its do-able. Try to let the wider ratio transmission lengthen your legs a little, and for pulling hills, etc. you have a direct gear you can split down to, with roughly a 250-300rpm split to keep in your powervand without either a.) being drug way down in mph before you can downshift, or b.) run rpm through the roof when pulling. a gear swap may be in order, but if you can get rpm to 1900-2000 at 65-70, and you hit a hill, drop one whole gear to bring rpm up to 2500 to pull with. if you drop a little more speed, you can split that half gear to get you back into rpm. The direct side is where your pulling power is anyhow. if i was going to build one of those, i would want to be able to cruise around 75mph anyhow. free flowing exhaut, hpop, stage 1's and a turbo of your choice would make a sweet tow pig with the drivetrain to hold the power without issue for miles and miles.

Jason · Jun 5, 2012

i think that 6 speed spicer may be too long winded between gears to be worth it, and would run out of steam quick. a 9 speed coukd work, if cheap enough, flip the top two gears around, convert it to a 13 and viola! Poormans 13 double over. You would get your long top legs for cruising, and still have a decent ratio for getting the load miving. Two downsides are, it may be me, but a converted trans doesnt seem to have the split ratio of the real thing. coukd be in my head...my '06 379 has a converted 9 speed behind an Acert Cat, and my splits in that truck are just a smidge over 200rpm, almost worthless. 07 379 cow truck with a 18 speed, behind a modufied isx cummins, has a over 300rpm split which is about perfect, and its a 600rpm jump between whole gears. 2nd downside is youre going to have to plumb air and a compressor, bc contrary to popular belief, when you lose air you are stuck in the high side of the box. Air forces into the low range...NOT fun when youre loaded.

Vader's Fury · Jun 6, 2012

Beans71086 said:
6+ spd spicer, but I like to shift gears. As far as a auto goes probably an Allison 2000 if you could find the wiring to make it work with your 7.3.

I thought about running an manual. I actually prefer a manual to an auto when towing since I don't plan to make big power with this truck. A manual will live with just a small clutch upgrade (which I already have) compaired to a fully build auto (5k+). Problem is the gear ratio's in a 6 speed leave something to be desired when trying maintain speed. They also are really close down bottom then tend to have large rpm jumps between the upper gears. Makes it hard to drop just a few hundred rpm when running at 65-75 to maintain speed.

Wiring should not be to big of an issue I would believe. I figured a pcs could do the controlling.

Vader's Fury · Jun 6, 2012

Jason said:
Manual. I love those little lo-pro 4700's, id like to find a 7.3 5 speed with air ride.

Anyhow...im not sure what the ratio in them is but i can imagine its steep to comoensate for low hp. For having a decent cruise speed and mpg when towing, id try to find a lighter duty 13spd. Ive seen a few put into dodges, and chevy's, so its do-able. Try to let the wider ratio transmission lengthen your legs a little, and for pulling hills, etc. you have a direct gear you can split down to, with roughly a 250-300rpm split to keep in your powervand without either a.) being drug way down in mph before you can downshift, or b.) run rpm through the roof when pulling. a gear swap may be in order, but if you can get rpm to 1900-2000 at 65-70, and you hit a hill, drop one whole gear to bring rpm up to 2500 to pull with. if you drop a little more speed, you can split that half gear to get you back into rpm. The direct side is where your pulling power is anyhow. if i was going to build one of those, i would want to be able to cruise around 75mph anyhow. free flowing exhaut, hpop, stage 1's and a turbo of your choice would make a sweet tow pig with the drivetrain to hold the power without issue for miles and miles.

This is exactly what I plan to set up. 7.3 with a with a full air ride rear supension.

I did not thing about trying to find a 9 or 10 speed to go behind it. My primary thought was an auto but something with more gears than the 4r100 has. While the 4r100 would be easiest to do since I will be running a full superduty wire/computer setup on the truck, I wanna try to find a final gear ratio that will not have me turning 2600 rpm when cruising at 75. I need to look at the rear gear ratio in the truck so I can do some trans gear calculations.

Vader's Fury · Jun 8, 2012

Well I was able to get some info on the truck from the International dealer. I went out to look at the actual truck and of course all the label plates were either missing or unreadable.

It came with an 7.3 idi engine, Allison at545 trans, and a Spicer F-155 rear geared with 4.33's.

Using a .72 final trans gear ratio I will be doing 2250 rpm at 75 mph. I was hoping to be closer to 2000 rpm as that always seems to be a sweet spot witht the 7.3 for fuel mileage. I will be looking into a gear swap for the rear but as of right now I dont believe it will be necessary to get me close to where I wanna be.

So I am thinking for simplicity a manual would be a lot easier choice(lack of electronics) but that will limit who is capable of driving the truck. While I will admit, 99% of the time I will be driving the truck, when you get on long road trips it is nice to be able to pass the wheel to someone else for a period of time and get some time to relax.

Also the other challenge with a manual will be the clutch setup. This truck is already equipped with an auto trans so the shifter and cable linkages are already there. The actual programming could be controlled by a pcs. I believe that elite is working on getting the bugs worked out on a 5R110 with a pcs.

So are there any other options that would be worth looking into as far as automatic transmissions are concerned? Like I said I have a 4r100 and while that would work, I am looking to see if anything would be better

Edit: I just looked up the gear ratio's of the 4R100 and the 5R110 and 3rd and 4th in the 4R100 is the same as 4th and 5th in the 5R110. So from that point I don't see any point in using the 5r over the 4r. Getting moving the extra gear will make things a little easier but when traveling at highway speeds the rpm jump will be the same with either trans.

Beans71086 · Jun 8, 2012

If your still looking into manuals that 7 spd spicer "6 plus" I was talking about has a .74 over drive in it, which is a lil higher than the 545. If I'm not mistaken there's already a bracket under your dash for a clutch pedal, so..... All you need is a clutch, clutch rod, and tranny.

http://i1103.photobucket.com/albums/g464/Beans71086/402c6700.jpg

Vader's Fury · Jun 11, 2012

That sounds good. I have been working the numbers and anything in the low .7* range should work for what I have in mind. The issue that I have and have been trying to find an answer for is to have a gear between the 1.0 direct and the .7* overdrive gear. That way when hauling a load and having to climb a grade I don't have a jump of 800 rpm from just one downshift.

I have looked into the over/underdrive units, but the gv will def not hold up and the u.s. gear seems to be discontinued.

The 6R140 auto trans behind the 6.7 has the gear ratio setup like I am talking about.

1st 3.97
2nd 2.32
3rd 1.52
4th 1.15
5th .86
6th .67

I do not need those exact ratio's but that is the idea that I am looking for. I wonder how hard it would be to control that trans with a stand alone controller like a pcs.....

TrailerHauler · Jun 19, 2012

I would look at, at least a 9 speed manual if it's going to be a dedicated tow rig. It would help out a lot making up for a lack in power.

Vader's Fury · Jun 19, 2012

What would you consider a lack of power? I'm planning for a minimum of 400 rear wheel horsepower. Although that number easley change up or down depending on the transmission i choose and a few other variables. I would love to be capable of 5-600 HP but able to pull it back when towing heavy.

TrailerHauler · Jun 19, 2012

Vader's Fury said:
What would you consider a lack of power? I'm planning for a minimum of 400 rear wheel horsepower. Although that number easley change up or down depending on the transmission i choose and a few other variables. I would love to be capable of 5-600 HP but able to pull it back when towing heavy.

I figured the 7.3 going in this would have mild mods maybe putting you around 350. In my opinion when your heavy, on steep grades and acceleration you'll want either power or more gears. 400 HP is a better number than I had in mind, but I still like the idea of only dropping a few hundred RPM to either gain speed, or maintain speed when the engine just doesn't have enough balls.
And it seems like throwing a manual behind it would be easier and cheaper. There aren't many draw backs if its strictly a highway rig.

Vader's Fury · Jun 20, 2012

I agree with the ability to drop a gear and pick up only a few hundred rpm. The problem that I am finding is that in order to have the ability to do this, and still have a good highway gear, will require a trans with 2 gears with less than a 1.0 ratio. I am having issues finding a trans with less than 13 gears that fits this need.

While having 13 gears is not a big issue (just gives me more gears to choose from) it just seems excessive for my needs. Also running through all those gears when in the city or townships will get old quickly. Also it limits my options on who else can drive the truck when going on long trips.

Guess I need to continue to look around for available trans and there gear ratio's.

Jason · Jun 20, 2012

You almost never use all 13. Ill gross 100k lbs and use 1,3,5,6,7,7od,8,8od. Never use low unless on a steep hill stopped. Its just nice to have that half gear to grab a few more rpm for accelersting, climbing, or enggine braking.