Spicer 7 speed to Fuller 13 speed

SuperSonic

SuperSonic

El Vato
Joined
May 31, 2006
Messages
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I'm looking at a 2000 F750 with a 300hp 3126 CAT to build a dump truck for our business.
Other than some sheet metal work and needing a good going over it seems to be in good shape. Problem is that it has the spicer 7 speed trans. Everything that I have read tells me that this transmission is a flaming pile of dog chit. Apparently they like to grenade on the 4-5 upshift, and generally don't shift worth a crap.

What I would like to do is swap in a fuller 13 sp. I am very used to driving this transmission, there is plenty of room for it, and the truck already has an air system for the brakes, drop axle, and seat.

What I'm wondering is, what is the best model to suit my needs? It definately needs to have a decent overdrive ( it has 22.5 rubber but 4.88 gears and will spend quite a bit of time on the interstate @70mph).
There are a ton of model numbers to cipher through while searching the salvage yards, and I have no idea how fullers system works.

Any medium duty gurus lend me a hand? I'm stumped!
 
that i can help with, what kind of TQ does your Cat put out? here is a model# and its break down
Model RTO12513
Road Ranger Twin Countershaft Overdive (some have an X) 1,250 lb/ft TQ 13 speed
 
damutt said:
that i can help with, what kind of TQ does your Cat put out? here is a model# and its break down
Model RTO12513
Road Ranger Twin Countershaft Overdive (some have an X) 1,250 lb/ft TQ 13 speed
Click to expand...
That would be a good choice since they are obsolete in the class 8's and can probably be bought cheap. It's a single over drive and maxes out at .87:1

$950

Parts list.

More

My advice is if you buy one either rebuild it yourself or have it done by someone you trust. I've had two "reman" Roadranger transmissions go bad recently. One didn't make it 3 months and the other lasted 2 years but had a bent mainshaft. Always had a vibration and only found the bent shaft after it ruined a few bearings.:nail:
 
That's easier to understand now. I knew RTO is overdrive and that the last two numbers is usually the number of speeds.

I think the engine is rated at 850ft.lbs. (don't quote me on that)
I am probably going to get the ECM reflashed to the highest factory setting (I think 330-350) and do a fuel temp sensor mod. Probably put a little better charger on it (68mm s400). I plan to put an exhaust brake on it but 3126's are pretty bad about dropping valves as it is. Do they make a better valve spring for these that won't wipe the cam out?
I'm guessing that this is SAE1 bell housing? Probably 1.75 10spline input?
 
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that i dont know
the only CAT that i have is the litle bother to yours the 3116 mech injected
glad to be able to help with the tranny
 
Somebody correct me if I'm wrong but I think the RTOO is a little bit smaller than the RTO. Might be easier to put in a meduim duty truck. I know there's a few people that have even put them in one ton trucks.
 
Not sure about physical size. The RTOO is just a double OD
 
I would give Cincinnati truck part a call. I think that they would be able to help you out.
 
RT's, RTO's and RTOO's are all older style transmissions. The newest model you'll find is most likely a 14613. Chris I would look at an RTLO for less noise (really stressing on the less noise) and easier driving. Something like a RTLO16913A has a standard .73 overdrive which would yield 2393 rpm at 72mph with the 22.5LP's on it. You could swap tires to 11R22.5's when its time or change the ratio's. Standard input's are 2" 10 spline, you can find 1.75" inputs but they are more rare in the twin countershaft units. Your 3126 should have an SAE #2 flywheel housing on it, and you can put a #2 on whatever fuller you want to match. A good idea is to use the "pot" style flywheel and an "easy pedal" 14" dual disc from Eaton. The single discs are garbage.

-Tom
 
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