RE: MANUAL VS. AUTOMATIC TRANNY

[Mex-Busnut]

All other things being equal, (weight, engines, tires, driving habits, etc.), how much difference is there in fuel economy between a bus with standard transmission and one with automatic tranny?

When we were running conversion vans in the craze of the seventies, we typically saw a 10-15% improvement in standard over automatic. Has anybody done a swap either way and seen a difference?

Thanks in advance!

Dr. Steve, central old Mexico

[buswarrior]

In the old MC7-8-9-102 days, in wartime service, the stick was considered worth a mile to the gallon better than the auto.

So, 6 mpg instead of 5 mpg.

But, the burned clutches by hired hands evened out the profits...

Seeing as to how the guy paying the fuel bill is doing the driving, a busnut with an auto, who doesn't just floor it, can close that gap considerably.

Considering the relatively small mileage a busnut does, there are much greater variables than fuel economy to the selection. Age of knees is a big one...

happy coaching!
buswarrior

[Lin]

Just did the switch and went to bigger injectors.  So far the mileage is about the same.  It was about 7.5 before and first fill after was 7.9.  I don't really expect much difference.

[Barn Owl]

I don't think I could get a manual 4106 to my house. Too steep and tight. I like the auto enough to take the fuel hit.

[DMoedave]

I have had my coach for 14 years and i was ALWAYS a clutch and shift kinda person. With our auto, i cant believe the difference in driving. we went from 10mpg with a 4-71 to 8.5mpg with a 6V-71 and an auto (and drop box). That was hitting the pedal pretty good. Laying off the pedal and lowering speed to 60 i can get back up to 10 mpg again. This is all flat land driving. Now that i can go faster, i am driving slow again lol. Oh boy and 10 4 on the knees! First day in 3 weeks i could walk without a limp,ace bandages, and a bottle of advill!

[TomC]

If you have a bus with a 4 or 5spd manual, it just isn't enough gears for the kind of driving we do-in steep RV parks, etc.  If you have a 6spd or better, then yes it would work.  But-with me after 1.3 million miles of driving nothing but a 13 spd (still the best manual transmission made [or the 18spd]), I REALLY enjoy the Allison in my bus (V730).  So much so, I had the 13spd taken out of my truck and had the Allison HT740 4 spd installed.  With 11R-24.5's and 3.55 gears, that gives me a comfortable cruise of 65mph @ 1830rpm, or a really economical cruise of 55mph @ 1550rpm. 
Pure and simple-once you drive a bus with an Allison, no matter what the fuel mileage is, you won't want to go back to grinding gears and pumping the clutch pedal.  Good Luck, TomC

[Lin]

As mentioned above, I recently put an Allison in.  We've driven it between 4 and 5 hundred miles.  Every time I open the front door of the bus and see the Morse shifter where the 4-speed used to be, I smile.

[robertglines1]

using eaton 10 spd autoshift.clutch to get rolling then automatic..with over drive..shifts self after rolling must clutch when stopping or going into reverse..

[lostagain]

My new (to me) bus has the HT740. This after driving nothing but manual buses all my life. The auto is SO nice. You still have to shift it by hand to make it perform at it's best, but it is so much easier in all aspects. The only downside so far, is that it puts a lot of heat into the engine via the coolant. I will look into some additional oil cooler, or an other filter or oil tank to shed some heat before it goes to the engine.

JC

[TomC]

JC- I did exactly that with a Hayden transcooler with 1" passages with thermostatically controlled fan.  I installed it on the hot side of the transmission before the regular cooler.  Hence, the auxiliary cooler will take alot of the heat load out before it even reaches the engine.  Because of space, I mounted it on the right side transmission door (V drive).  This sounds backwards, but the fan pushes the air from the engine compartment outward.  This is because the big engine fan has too much power and overpowers the little electric fan.  Even with the hot air of the engine compartment being used, it is still is cooler then the trans fluid.  Ideally, you could mount it in front of the engine compartment out of the push of the big engine fan, then you could suck cool outside air through the cooler.  Good Luck, TomC

[steve wardwell]

For us the path from manual stick to auto Allison is a one way trip !

[kyle4501]

In the fun car, a stick is preferred, but in the RV, my preference is for the automatic. Sure the manual stick was great for the hound, but, we ain't driving for the hound & we ain't stopping at bus stops. We're parking these things in campgrounds & other tight places that weren't designed for buses - all that can be rough on a clutch - especially if the driver looses a little bit of his touch from not driving it often enough.

Then, there is the problem with stop & go traffic. I loose fondness of the stick shift even in the fun car when this happens.

Let's not neglect the advantage a torque converter has when it comes to starting out on a grade. (PLUS)
And, the extra heat the transmission must dissipate. (MINUS)

I chose a bus model that I wanted & since there is only a limited number of those to choose from, I had to take what I got & deal with installing the engine & transmission I want.