RT 910 10 speed retrofit from 5 spd

[401bluebird]

High-
After years of waiting, I am about to refresh my GMC chassis 1960 Bluebird all American Motorhome conversion. My 401 GMC v6 is tight and runs well. It has a Clark 5 speed which doesn't offer enough gear choices for this marginally powered coach.

My friend, a diesel bus mechanic, suggested I find an Eaton/Fuller RT 910 road ranger 10 speed trans. Says they are very common and can be acquired for fairly cheap. It offers the obvious closer gear spreads, plus as a bonus, an overdrive final ratio; something I can really use.

My bus chassis has the large bell housing, which I am to believe is an SAE 2 size. Has anyone done such a swap before? My mechanic friend said that there are two basic shifting mechanisms, one is cable, the other is mechanical rods.

I appreciate any insights offered.
-Andy Carlson
Ojai CA

[George Bongert]

Originally Posted by 401bluebird

High-
After years of waiting, I am about to refresh my GMC chassis 1960 Bluebird all American Motorhome conversion. My 401 GMC v6 is tight and runs well. It has a Clark 5 speed which doesn't offer enough gear choices for this marginally powered coach.

My friend, a diesel bus mechanic, suggested I find an Eaton/Fuller RT 910 road ranger 10 speed trans. Says they are very common and can be acquired for fairly cheap. It offers the obvious closer gear spreads, plus as a bonus, an overdrive final ratio; something I can really use.

My bus chassis has the large bell housing, which I am to believe is an SAE 2 size. Has anyone done such a swap before? My mechanic friend said that there are two basic shifting mechanisms, one is cable, the other is mechanical rods.

I appreciate any insights offered.
-Andy Carlson
Ojai CA

Greetings 401bluebird!

I'm not sure what you will need to make this transmission swap, and the Fuller Roadranger 10 speed would be a good choice for your application. However, there is one drawback to the Fuller Roadranger transmission, that being that it is a non-synchronized transmission, (I assume your Clark 5 speed IS synchronized) meaning that you will have to learn how to double clutch when shifting from one gear to the next, or learn to shift gears without clutching by using engine RPMs. In most truck driving schools, it is recommended to double clutch these transmissions, but I know many over the road haulers who use the engine RPMs and no clutch method when shifting gears. I once drove a sweet corn truck for neighbor who taught me how to shift these transmissions without using the clutch, and they shifted as smooth as silk. I'll quote what he said to me as he taught me how to handle these transmissions: "We only use the clutch on these (Fuller Roadranger) transmissions for three things~~~stop, start, and back up"! This sounds like an interesting project! Good Luck!

[BillT]

That is correct that you will be going from a synchronized to a non-synchronized, but the Road Ranger is just about my favorite trans. Also want to say that the RT 910 is not an Overdrive. I believe the RTO 910 is though, but verify that info to be sure.

By the way, I "always" use the clutch when driving one.

[401bluebird]

Hello again- I found some new info in my search for RT 910 10-speed transmissions. Seems that the 10th gear is 1:1 direct for the RT 910. The RTO 910 however has a 1:1 9th gear and a 0.81:1 overdrive 10th gear. However, it was mentioned that the RTO-910 used a bigger bell housing size, an SAE 3 (Instead of SAE 2 as my Bluebird coach uses.

So I found a bus conversion site where one respondent suggested a Road Ranger RT 9509, a 9-speed trans with similar torque rating as an RT 910 and an SAE 2 bell housing size. This trans has a deeper 1st gear, plus a taller overdrive, 0.79:1 in 9th gear. Though this trans has broader spreads in each gear change, this has to be a huge improvement over my 5-speed Clark transmission.

I will go to some Truck Centers this week to see what is out there. I am hoping that my 401 V6 likes the change! Regards, -Andy Carlson
Ojai CA

[Nugget]

RT910 is a direct 10th gear, RTO910 is .81 overdrive. Also these transmission require an air supply to shift from low to high range. With a little practice the only time you need the clutch is taking off and stopping. These transmissions are larger physically so you should make sure it will fit under the floor.

[Nugget]

I build transmissions and rear ends at our shop and my boss been trying to get me to try a 13 speed behind my 401. I have access to core transmissions cheap but an automatic sounds better to an old man like me.

[BillT]

Good point about the Air Pressure. I forgot to consider that when we were talking 3 years back, lol.

Air Pressure shouldn't be that much of a problem though. A small aftermarket unit should even do fine.