.

[quickfarms]

There is a small 13 speed out there.

Be careful with a transmission with a deep reduction first gear. This could lead to issues just as using the stock transmission in reverse in low range.

What you should do is take the truck to a local heavy duty gear shop and see what they think.

The Allison is not a small trans

The stock Allison in these trucks is a MT654, that Allison considers obsolete and does not offer factory rebuilds.

An alternative would be a MT643, this is a very common Allison. It is a four speed but with the correct torque converter it should work just fine. There is a MT653 which has a super low first gear but this could lead to transfer case damage similar to the stock transmission in reverse in low range.

 

[Jason O]

I'm considering the small Roadranger (RT-6610, 6613 or overdrive versions of these), however they are only rated for 600 lb-ft of input. Maybe a larger 10 speed with the smaller SAE 2 clutch housing would be a good fit. It would not have the LOW gear that the 13 has, and may be a few inches shorter.

There is nothing wrong with the Allison in either of my trucks, and I see its advantages over a manual box while off-road, at the farm, or on a construction site. It just seems to make the truck such an awkward turd to drive on the road.

 

[74M35A2]

Does anybody know of a single case where an M939 series either is or has been converted to a manual transmission? I just picked up a 6 speed Eaton single countershaft and Cummins 8.3L engine combo, just for the trans, clutch, and flywheel stuff. I also have a huge double-counter 13 speed on a pallet.

Very open to clutch pedal ideas here. Also, I think the counter-shaft transmissions will fit and work, but need to clock the T-case to clear the front prop shaft?

Info? Pics? Stories? Anybody actually done it or have pics?

 

[Heavywrecker]

I have a 9 speed eaton and an aluminum sae bellhousing if anyone needs one


Sent from my iPhone using Tapatalk

 

[simp5782]

My 16spd swap will be interesting without the clutch problems

Sent from my SM-G860P using Tapatalk

 

[74M35A2]

It will be.

 

[grendel]

I wish I took pics of the one we did years ago. The frame rails are spaced at 34" - same as any HDT that takes the big transmissions. We swapped a "stacked" t-case that sent the front driveshaft under the trans, instead of beside it. Used a Peterbuilt clutch box. Similiar to a 916 set up. Look at the 916 or it's MET forefathers. This isn't rocket science, but MDT legos.

 

[74M35A2]

How does the 800 series clutch pedals mount and actuate? Through the floor like an M35? Or are they firewall mounted swing?

I should be able to rotate the T case for front shaft clearance on a double-counter tranny. Heard it does not need to go far.

 

[grendel]

How does the 800 series clutch pedals mount and actuate? Through the floor like an M35? Or are they firewall mounted swing?

I should be able to rotate the T case for front shaft clearance on a double-counter tranny. Heard it does not need to go far.

I'd use the Peterbuilt clutch pedal box I sent you. It's what we did.

 

[wcuhillbilly]

How does the 800 series clutch pedals mount and actuate? Through the floor like an M35? Or are they firewall mounted swing?

I should be able to rotate the T case for front shaft clearance on a double-counter tranny. Heard it does not need to go far.

800s go through the floor Peterbilt style, from there they swing off the frame. If going air brakes the inner pedal(looking up from under truck) can be eliminated thus making more room on the swing pivot. the Clutch pedal on the 800s is actually outside the frame rail and above the tool box, tight space under the cab corner/frame. I have heard that the counter shaft trannys will fit the air pac/MC by an inch or two, so it is doable.
Biggest thing is that your going to loose the front drive shaft for a while, until alternative means can be fabbed up. The T case will have to be moved back 12" for a 10spd and maybe more if going 13,15,18spd. the 10s are the shortest of the family, as they lack the extra gear case on the rear for the combos above 10spds. If anyone still needs measurements, I have a RT9513 laying in my yard, and can get my hands on an 10spd very quickly...
Note on Eaton Fuller Trannys.. The letters infront of the numbers will tell you a lot,,,,, R-"RoadRanger by Eaton, T--(cant remember,) O-"overdrive, L- Low gear, So,,,, an RTLO= Road ranger Trans, Low gear 1st, Overdrive top gear... or a RTLOO would be the same with a double overdrive.
Now look at the numbers.... Earlier someone posted an 6406- this is a 6 speed medium duty trans that is single countershaft. the first couple numbers is the series and torque- 6=6 series, 4= 4-600 torque input, separated by a 0 and the final 6 is the number of speeds,,,,6 speed. Remember Eaton derates most of their torque number by 20% for several years until the model proves itself, thus the 5306,6406,7206, and 8406 are all the same case, all 6 spds, but different series,,, 5,6,7,8, and all different torque ratings,,, the 8406 being the newest and heaviest.. thus they were building on the last 30yrs of R&D from road time....

The bigger trannys are very similar... the 9513 that I have in my yard is a 13spd, which is very similar to the 9 speed. but they are both double counter shafts unlike the 6 speeds in the previous paragraph. So,,, look out for your 6610, 9513 etc.. the last 2 digits will likely tell you the gears, and the front 2 digits will tell you the series, and the alpha numeric will tell you the combos... road ranger, low, overdrive, double low, or double over...
Ok,,, thesis dissertation over...

 

[Csm Davis]

Good thing about using the 939 series is the cab is about 4" higher than the 809 series and the Allison transmission is longer than the Spicer so more room to put a big manual in.

Sent from my SM-G930V using Tapatalk

 

[red]

List of the gear ratios, torque rating, length, and PTO speed of Eaton Fuller transmissions.
http://www.roadranger.com/rr/ProductsServices/ProductsbyCategory/Transmissions/PCT_486870

 

[74M35A2]

Thanks for all the info. I now have a 6 speed manual single counter and 13 speed double counter trans to choose from. The 6 speed is still mated to an 8.3 that came with the deal, so the flywheel and clutch and all that is there.

Am I seeing this correctly, meaning because the bellhousing is full bolt circle connect, then there is no trans support? Even on the heavy 13 speed unit? I think so. Can an aluminum flywheel housing on an 8.3L handle the full weight of a 13 speed trans with no further support? I would need an SAE #1 flywheel housing for the 8.3, which is kind of rare but does exist.

Has anybody else done this?

 

[Heavywrecker]

In most of the large truck applications, the transmission is supported from the bellhousing with no further support


Sent from my iPhone using Tapatalk

 

[red]

With the twin countershaft transmissions they require a mount. Most have a single mount going across the top at the rear of the trans (like a leaf spring). There are 2 studs on the top of the transmission, that's what the spring is bolted to. Some others (mostly Mack and some Volvo) use 2 round mounts at the front of the transmission, just after the bellhousing. The 10 speeds weigh about 600 lbs, 13 speeds even more.

From experience I HIGHLY, HIGHLY recommend using one with the rear mount. The front mounted versions add about 8 hours of labor to remove/install the transmission. Major pain in the ass.

 

[Heavywrecker]

Red no offense but many do not have the rear mount, it usually is just a damper for when the motor torques to reduce bouncing


Sent from my iPhone using Tapatalk

 

[red]

That bouncing cracks the bellhousing and adapter plate for those running without the rear mount on the transmission. That happens on pavement driven trucks. Those that go offroad it is a necessity.

 

[grendel]

Fab the rear mount, it won't hurt you. A couple of captured one ton chevy leaf spring bushings will do the trick on the two rear studs, some 3/16" 2x4" box tube and you're all set.

 

[74M35A2]

If I was hanging it off a full size ISX, I would probably just leave it. But off the back of an 8.3/8.9L, I may end up supporting it.

 

[Lukes_deuce]

I will be following this thread. Definitely a project I am interested in. I love my 813 but wouldnt mind a 931 in the future. The automatic kills it for me tho. Hopefully after a few measurements and drive train adjustments, it will be an easy install of a 9 or 10 speed. Good luck! Take pictures!