Jumbo - 97 F350 Project Truck

[cjfisher]

I'll start this build with a preface which I know will drive Charlie bonkers for having to wait.

Meet Jumbo...

Jumbo022010.jpg

This is a day or so after I purchased the truck in Feb of 2010 for around $7000 green backs. With the pending arrival of kiddo #2 we needed a bigger truck to hold us all as the ol' 87 F250 (6.9l diesel may it RIP) wasn't going to cut it anymore (not to mention it was drinking its own oil at the rate of a quart every 350 or so miles). I have always thought that the weak link of Ford's OBS workhorses has been the transmission and I have dreamed of upgrading the transmission ever since I bought the 97 in 2010.

Not to give too much away here in the first installment... but the RTO 6610 transmission has now been in the truck for 2 years and just shy of 20000 miles.

[heavydoc]

The people here will love this, I still wanna do something similar like this, just not sure on execution yet.

The Southern President

[Fellro]

This should be interesting. I knew a guy that ran a military truck salvage yard that put a DT466 and 9 speed in a mid 80's F350. Could always tell when he was coming through town.

[john112deere]

RTO 6610 is a ten-speed, right?

[cjfisher]

Ian,

You are correct. The RTO is a 10 speed... RT - Roadranger transmission, O - Overdrive unit, 66 - 660 ft-lb input torque, 10 - number of gear selections. transmission arrangement is a 5 speed gear box on front with a Hi/Low Aux range box in back.

Cj

[dustybumpers]

Ooooooo
Cool truck build. Drum roll please!

Sent from my SM-N960U using Tapatalk

[cjfisher]

So, as I mentioned in the first post I have always dreamed of changing the transmission (which I consider as the main weak link of the Powerstroke power train) out for something a little more in the medium duty realm. Some months after purchasing Jumbo I found an ad for dead International t444e motor. From that engine I was able to get my hands on the flywheel housing adapter needed for any future conversion. My original plan was a TTC Eso 7 speed swap.
In the mean time I purchased a cnc mill and dragged it home to my place (this was with the good ol' ZF5 transmission). Trailer plus machine was around 21k (yah, I only exceeded the book GCR by a bit). As I was just on surface roads it wasn’t too bad other than having to really ride the clutch to get the truck moving and having to go into 4 wheel low to back the trailer into the driveway. The mill weighs in around 16000#.
Shizuoka mill.jpg
The transmission swap really became serious in April 2016 while pulling my dad’s disabled truck home from Laramie, Wyoming. All told I was pulling around 15k and trying to keep the truck rolling at a reasonable pace was a bugger.
pulling dad home.jpg
There is a reason that the 97 F350 was only rated for 11k towed weight (and it sits between the engine and rear axle). The trip home was rough, as finding a gear the engine was happy with that didn’t require me revving the engine into the stratosphere (how did Ford come up with the red-line for the 7.3??) to keep the boost up and the truck at a reasonable speed was tough. After arriving home, I promptly started doing some digging and found that someone had done an Eaton RTO 6610 swap in a Dodge Ram. Two weeks of trolling the web later I found a RTO 6610 on Craigslist and the adventure was underway. Two days and 1533 miles later, this was sitting in my garage...
Rto6610R.jpg

[heavydoc]

The Southern President

[cjfisher]

All right Doc... keep your eyeballs in your head .

[cjfisher]

It took me a year and a half to finally get to the point where I was ready to begin the swap.. I found one or two forums discussing Eaton-Fuller swaps that involved re-mating the transfer case to the transmission using a cut down yoke that was then bolted to a coupler with the correct mating splines for the transfer case. Not a bad idea, but it would have added a considerable length (4+ inches) to the whole transmission/transfer case combination. I knew that some transmission tunnel mods would likely be required, but I was hoping avoid modifying the body supports running under the cab that stiffen the cab.
First things first - breaking the huge nut loose (with a 6 some odd foot cheater bar – the aluminum bar is bolted to the output yoke).
Rto6610 boltR.jpg
Then, I got to work dismantling the auxiliary transmission case to have a look at the output shaft. This is a shot just after I divorced the case.
Rto6610 Aux R.jpg
The RTO 6610 output shaft sure makes the original ZF5 transmission output shaft look puny. The splines (just visible at the top of the picture) on that guy are 2.25 inches in diameter. I didn't have enough hands to hold the other counter shaft. In low range there is approximately a 3 to 1 reduction. High range is direct drive.
Rto6610 Aux gearsR.jpg
Here is a shot of the main 5 speed gear box.
Rto6610 gearsR.jpg
The left most (course cut) gears are reverse, the next set to the right is first gear. Second gear and third gear are on the next sliding clutch. Now things get a little odd. The next gear is 5th (this is an overdrive transmission) while 4th couples the input shaft straight to the main shaft. The shift pattern is:
R 2 5
1 3 4