Transmission Choices

[TomC]

When deciding on a transmission, the only real question is-do you want an automatic or a manual?  Automatics come in two choices-first is the torque converter planetary gear fully automatic similar to the automatic in your car.  These are made in 3, 4, 5, 6spds (I don't include the 2spd Allison-just not enough gearing) and made primarily by Allison with ZF and Voith also in the picture.  Then there are automated manual transmissions. This is where the manufacturers take the stick shift out and replace it with electric shifters that work through the transmission and engine computer to shift for you.  ZF makes a 10 and 12 spd transmission that is VERY expensive to work on-so much so Freightliner dropped it from their line.  Volvo has their own in their trucks and buses. Eaton/Roadranger makes the bulk of the other automated transmissions that come in three variants.  First is the Autoshift that works with an electronic engine (the Autoselect works with a mechanical engine-of which I do not suggest-it is too much work and rough shifts, miss shifts are among the negatives) and has a manual foot operated clutch just for stopping and starting.  These are available in 10spd (both B and C ratios) and 18spd.  Next is the Ultra Shift, which is available in 10spd and 13spd that has an automatic centrifugal clutch that has a tendency to only last 80-100,000 miles since it is slipping a bit all the time.  The newest is the Ultra Shift 2 that has an electrically controlled clutch available in 10, 11, 13, 18spds.

Then there are the Eaton/Roadranger multi spd manual transmissions.  If you stay under 860lb/ft torque, you could use the 6spd fully synchroed overdrive transmission.  Over 860lb/ft but up to 1450lb/ft, there are 6spd and 7spd direct and over drive transmissions that don't have any type of splitter to contend with, but have enough gears to be an upgrade from the stock 4spd.  The next is a 9spd that can be selected in 3 different ratios. A is close, B is wide, X is an extra low for construction.  Many 10spds are available.  You have the 8L that is an 8spd with 2 lows for construction, A ratio that is a close ratio (more then sufficient for buses) and the C wide ratio that we use a lot in trucks.  The 11spd is the 8spd with 3 lows for creeping use like for dumps and concrete mixers that need to go slow behind a paver.  Then the excellent 13spd and it's cousin the 18 spd with 6 more low gears primarily used for heavy haul.  Lastly is the 15spd that is a close ratio 10spd with 5 selectable gears for low-actually having only 12 progressive gears, the other 3 are so close to each other they are considered repeat ratios.

Many choices.  I still believe for the vast majority of us that are not familiar or trained on a Roadranger type transmission, the Allison Automatic is the best choice-even with getting less fuel mileage and creating more radiator heat.  Allison is so good it is the transmission of choice for the military-including tanks (the military has purchased over 250,000 Allison transmissions since the '50's!)  Good Luck, TomC

[Lin]

Tom,

Thanks for the short course.  I personally think an automatic transmission is perfect for cars and RV's.  Only the special needs of the particular service or the particular driver could dictate the choice of a manual.

[NeoplanAN440]

Thanks for all the info!!!

And yes if i had all the funding for my bus that i wanted ,i would stay with a Automatic, in my case a B400 or 500. But for me, my Bus is a Hobby (maybe more )and a low cost way to get out and travel and forget the work week !!  so i have to make cuts and find the the best engine transmission combo that works in my budget and is in my area available!!

in a perfect world i would be working a my new bus   but right now , i have the same fun with my old workhorse and enjoy the view and the moment !!

just my 2 cents

[CrabbyMilton]

Automatic transmission is a long proven product. As a 25 year deliver driver, I can't imagine or want it any other way. Most buses and all fire trucks have automatic as standard equipment simply because most customers WANT IT. Full size pickups don't even offer stick anymore and that was unheard of years ago. In a bus, you want fast smooth shifts but automated manuals will always be around for you people that like that stick shift feeling.

[bevans6]

"will always be around for you people that like that stick shift feeling. Smiley"

I wanna be sittin' low and lookin' out, with my hat on backwards and my mirrored sunglasses and I wanna be shiftin 8 times to get up to 10 mph and half way across the intersection!  THAT is livin' life large with a manual tranny, you bet!  Straight pipes and over-fueled Deetroit belchin' smoke and noise!  I may even take up smokin' a stogie!!!

      

Brian

[artvonne]

  Anyone know which manual trans is the easiest to shift without the clutch?

[Lin]

Allison

[artvonne]

Allison

  Lol

[HB of CJ]

My old 1974 Crown Supercoach 10 wheeler ex schoolie had the famous (infamous?) RTO 910 10 speed and the coach was an absolute blast to drive...and shift.

More like riding and shifting some dirt bike than shifting a heavy truck tranny.  The shifter moved about one inch or soos and took about 2 to 3 pounds of effort.  Very close gears.  Usually started in 2nd.

At 55 mph you could run in either 8th, 9th (direct) or 10th gear, which was a 22% overdrive.  It was very easy to keep the mill humming in "the sweet spot" which for me was 1500 rpm.  Small Cam 250 Cummins.

I always used the clutch.  However, the tranny was a dog box and one could easily miss gears if you were not paying attention.  It was COOL shifting 5 or 6 times to clear a big intersection.

For those who dig this kind of stuff, the ratios were about... .82, 1.00, 1.26, 1.59, 2.00; // 2.44, 3.07; 3.87; 4.88 and 6.15.  Had two reverse gears; one low and one about 2.44 to one.

This meant that you could go real fast in REVERSE, then practice your bootlegger turn reversing course.  I did this in icy 6" snow with the tandems locked up.  Dumm, but fun!

Starting up super steep hills like some onramps on Interstates were no problem, you started usually in 2nd and rowed your way up.  In no time you were doing the speed limit.  HB of CJ (old coot)

[artvonne]

  The 7 speed..

  Would it be totally and utterly impossible to fit a 7 speed in a 4104?

 

 

[TomC]

To fit a 7 spd in a 4104 with the 6-71-you'd need a angle drive similar to the 4106-where the angle drive is after the clutch-not at the end shaft like the 4104-because of the extra torque from the lower gears of the 7 spd.  With enough machining, and designing, you could make it work.  Personally- just replace the 6-71 and 4 spd with a 6V-92TA and V730 Allison-then you'd have a real hotrod!  Good Luck, TomC

[HB of CJ]

I made a mistake with the RTO 910 gear ratios.  The high side is correct, but the corrected low side ratios are ... 5th; 2.57, 4th; 3.14, 3rd; 3.95, 2nd; 4.98 and 1st; 6.27.

The 9th-10th and 4th-5th drop is 22%.  The 5-6th drop (range shift) is around 1.285%.  The rest of the drops are right at 26% if you really want to know.

However...all said and done, as I age, my NEXT Bus Conversion may have an Allision Automatic.  Much easier to drive, particularily in city traffic.  HB of CJ (old coot)

[RJ]

Art -

  Would it be totally and utterly impossible to fit a 7 speed in a 4104?

How much $$ do you have?

Not only would you need to use the 4106 and later bevel gear set-up, you'd also need to swap in the rear axle assembly, too.  Reason being is that the pumpkin is on different sides of the coach centerline between the 4104 and the later models.

There's also the question of mating the 7-spd to the bevel gear housing, cutting out the hole in the bulkhead for the driveline to fit thru, not to mention fabricating the necessary shift linkage and other minor details like that.

OTOH, if Jay Leno can stuff a 6V92TA into the rear of a Flxible Clipper. . .

FWIW & HTH. . .

[pabusnut]

I've often wondered why GM stuck with the 4 spd for so long(prior to getting out of the bus market).  The six-speed Prevosts seem to be just about right for the 8V71 or 6V92.  I can't imagine that a 6 ro 7 speed v-drive configuration would have been that much larger(longer)?! 

As a Mechanical Engineer, I can envision how to reverse engineer the existing spicer into a modular unit, which could then be used for either a manual trans or an automatic, as the "V" portion would be a "module."

Understanding marketing and "bean counting" a little bit, I can see that it would not have been worthy of the engineering and re-tooling expense, especially considering the limited market for v-drive components.


Now if I were independently wealthy.....

Steve Toomey

[CrabbyMilton]

It's often fun to play "what if". What if this, that, or the other did or did not take place how would it be now. I would imagine that if GM was still in the bus buidling business, they would have abandon the V drive configuration since no bus to my knowledge is built nowadays has that. Be careful though, while you can have fun with it since it doesn't matter which subject you pick, you can also drive yourself buggy putz too.