looking for allison 748 for conversion

hargreaves · August 24, 2009, 12:34:43 PM

Hi guys , I am converting my 102A3 to an auto,and I'm missing one key part, the transmission. I want to use the 748 . I am removing a 6v92 mechanical with 5speed fuller and installing a 6v92 DDEC 11. I have all the accessories, just need the tranny. Does anyone know of someone in the area that may have one for sale,I'm on the west coast, Vancouver to be exact. Also any issues I might run into while converting would be of great help.

Lin · August 24, 2009, 12:39:04 PM

I might have a rebuilt 740, but I don't know if that would work.

NJT 5573 · August 24, 2009, 03:13:50 PM

Maybe I'm just getting to old, but I would be doing this the other way around with my bus if I could.

All of the electronics were government emissions driven in my opinion. The good stuff is the non electronic.

You could sure save alot of expense and time by at least going with the non ATEC transmission. I guess if you have it all though, you are aware of the mile of wires that run to the front of the bus, the electronic shift pad, the ecm and all of that. The cooling pipes and heat exchanger are also extensive under my bus. I have been dreading a $10,000 repair bill on my HTB748R too, secretly wishing I had a more repairable 740.

I think when mine dies, because of the short engine compartment of the Model 20 that its going to get a Series 50 and a double OD 10 speed.

I do like the Allison, but I know it's costing me about 2 MPG and I don't mind shifting a manual, done it all my life...
but 2 MPG seems like some real crummy engineering to me. The very best my 6V92 with HTB748R has ever gotten is 6.0 MPG. The average is 5.3, and I see alot of 4.9 if I push it. It's hard for me to be any kind of a fan of DDEC or ATEC with those numbers.

I think I have seen a low milage M11 and Allison set up for sale in Phoenix for about $7000. If I had your setup and I was looking for improvement I would try something like that where I would have an engine for the future with a transmission I desired to handle the shifting.

For what you will spend to get a good 748, you can probably find a Ultrashift and change the DDEC 2 over to DDEC 4 to run it.

buswarrior · August 24, 2009, 07:08:14 PM

Yes, busnuts, the 2 pedal variety automated non-synchro transmissions are a great thing to add to your later model engine electronics.

No clutch pedal, centrifugal clutch, you can't break it, it makes a perfect clutchless shift on every shift, never gets confused as to what gear to use, and you just set the throttle pedal at whatever depth gives you the rate of acceleration you desire.

Do not confuse this with earlier generation Auto-Select or Auto-Shift where the driver had to be smart with the throttle pedal or get stuck in the intersection, and that had a clutch pedal.

Huge numbers of the modern coaches have been optioning these for the last 5 years.

Stick it in "D" and go. Just don't go too hard, or granny's neck is going to snap fore and aft on every shift.

happy coaching!
buswarrior

hargreaves · August 24, 2009, 08:24:10 PM

I have been batting this around for quite a while trying to decide which way to go. The electronic version engine alone i understand I will loose 1.5 miles per gallon unless I change it over to DDEC 111/1V. I understand I will loose some milage by just changing it to an automatic I currently get 8 imperial miles to the gallon.
I know this is another topic altogether but the other halve cannot push the clutch pedal down let alone try to find what gear to use.I figure if I want her to do some relief driving it will be with an auto. It sort of makes sense to go with the 740 since the mechanical engine has only 35,000 miles on it.and runs great. I would miss cruise control but that is not the end of the world. What diff ratios would work the best? I think mine is 3:73 to 1 . It certainly would be easier to install.

Lin , when is the best time to call you. Gerry

buswarrior · August 24, 2009, 08:55:17 PM

There are fine cruise control systems available that will make a mechanical 6V92 and 740 sing down the highway. Pete/RTS/Daytona on here sells one, there are also others.

8 imperial mpg? That is somewhere 6.6 mpg US.

I gave up on imperial and figure my stuff in USG due to the ratio of the audience on the boards, CDN to USA.

For comparison, running long haul to Jack's party, my MC8 with stock 8V71 and 740 gets 7 mpg US at 60 mph and 6 mpg US at 70 mph. It is said that the equivalent 6V92/740 drive train will squeeze a few decimal points better.

Come off the big road, and those figures will degrade fast. Messing around in a bunch of city driving will pull you down towards 5 mpg for those tank fills. Keep it in perspective, this is much the same degradation as you'll see with your personal transport between city and highway driving.

The biggest loss in an automatic is if you use the ability to launch it like a rocket ship. If you are gentle with the throttle, you match the rate of acceleration of what you do now with the manual, you won't lose as much as some do. That faster take off costs money, and you can CHOOSE not to floor it off the line. Beware, the launch of an automatic is intoxicating, and you will want to drink of it deeply!!

Don't rule out a common and somewhat simpler 740 swap to your current mechanical 6V92, it's the total bill and how much time before anything comes close to breaking even, if that's part of your equation.

I'm not sure about that information you have about early DDEC losing you fuel economy. Horsepower for horsepower, I've always been led to believe that DDEC saves fuel, as it can change the amount of fuel that gets sprayed in ways that mechanical cannot.

However, if you want to wire it all up because you want to, you've got my full support for that too!!!

happy coaching!
buswarrior

TomC · August 25, 2009, 06:47:38 AM

If I were you, I'd keep the mechanically operated 6V-92TA and run a mechanically operated HT740. Both are very reliable. Even though you might see a bit of a fuel economy increase with the electronic engine, all you need is one electrical failure and the towing and repair bill will more then offset any savings you might have seen up to that point. Unless you live in one of the smog states, I would stay with all mechanically operated equipment. Good Luck, TomC

hargreaves · August 25, 2009, 10:28:43 AM

I am convinced, staying with the mechanical set up makes much more sense. As for keeping my foot out of the gas pedal that won't happen. I work in a transit bus garage, and the only way we drive 'em is full on or full off lol. thanks for all the info guys, it definitely helped in making my decision. Gerry

mikelutestanski · August 25, 2009, 10:39:00 AM

hello: I have a used rebuilt 740 with most of the parts required depending on your engine.. Call mike if you are interested. 352 489-1581 the bad part is that I am in Florida 34432 about as far as it can be from you.. I changed my MCI 7 from a manual to a 740 then changed the whole plant to a cummins L10/b400R
Regards mike

belfert · August 25, 2009, 10:40:25 AM

I have an 11.1L Series 60 DDEC III with Allison B500. My bus weighs right around 38,000 with no cargo or passengers. I get an honest 7.8 to 8 MPG on a yearly 4,000 mile trip with 8 or 9 passengers and the luggage bays full to the gills with a 500 lb trailer. My MPG numbers even include up to 40 hours of generator use.

I have seen numbers up to 8.8 MPG on one tank with no generator use and I fill to the same level every time. I think electronics get you better mileage, but they never made a Series 60 without DDEC either.

NJT 5573 · August 25, 2009, 03:25:31 PM

Gerry,

Thanks for the understanding about DDEC 2 to DDEC 3. Several years ago my local DD Dealer let me go through all of their old service records and I discovered that Greyhound replaced all of the DDEC 2 computers with DDEC 3. Wow, I guess if they picked up 1.5 MPG that was a worthwhile expense.

When I had the 05 with the 4 speed I used to let the kids drive alot. I would just put it in 3ed gear and turn them loose. Here on the west coast they could drive alot of miles that way. It would run from Blaine to central Oregon and from Redding to Bakersfield for them just fine without shifting. It kept them from speeding and out of trouble just fine. We change seats just like you would in a truck, just stand up and swap drivers.

Doug1968 · August 25, 2009, 08:30:56 PM

Gerry,

How long have you had your 5 speed bus? Or better yet, how long did it take you to get so you could shift the transmission up and down without problems?

I have a 102 with the 5 speed. I have never had problems shifting anything I ever owned, but boy this bus has been difficult. Up is not a problem, but when I have to go down it's terrible.

What do you have planned for your 5 speed and the clutch components? I might be interested in having a spare. I live in Vancouver, Wa and wouldn't mind driving up to visit with you sometime.

I have the same issue as you. My wife can't push in the clutch and it takes both of my legs to get it in?? She will never be able to drive the 5 speed and I worry about a time that might come where I need her to drive?

Good luck with the swap and I am serious about the visit to see you.

Doug

buswarrior · August 25, 2009, 10:05:10 PM

I have driven a 102A3 with the absolutely lightest clutch in anything I have ever driven. 8V92 and 5 speed. No kidding, it was no heavier than one in a Honda.

A couple of brown colored coaches in the Coach USA/Coach Canada family back when it all started in the late 1990's, that were rumored to have come all the way up here from San Diego for the busy season. Fleet name maybe started with a "B"?

What a joy to drive! Everything was snug and just the way it should be. Obviously a lot of pride in ownership.

Unfortunately, it was back before I paid attention to the finer details.

I'd really like to know how that clutch was so light.

happy coaching!
buswarrior

hargreaves · August 26, 2009, 02:56:50 PM

Hi Doug the package will be sold, I have been driving it for two years, this summer is the first time I got a handle on the down shifting. the way I do it is on an uphill grade, watch the tach until it gets to 1500 rpm. then leave the throttle on the floor do the double clutch show,and go to the next gear. Bear in mind this has to be done quickly. the hardest part is finding the gear.When it works it is like butter. Email me and we'll get together.

NJT 5573 · August 26, 2009, 07:55:44 PM

If you are having issues shifting down, they are easy to fix. With a 5 speed, get the top MPH in each gear by running it against the governor and holding it there. Write it down. If its 65 MPH in 4th at the governor then when the speed drops to 67 MPH, take your foot off the throttle a little, slip it into Neutral, floor the throttle so it hits the governor and wait a second or two for the bus speed to drop to 65MPH and it will drop right in. Don't use the clutch, you will just mess yourself up. Shifting this way allows you to have the complete pulling RPM range of the engine available until you need to make the next shift. When you get down to the lower gears, you may need a 3 MPH cushion to get the gears to slide, but thats all there is to it.

I use the governor shifting up all the time as well. Hit the governor, take it out of gear,wait for the engine RPM to slow down a couple seconds with turbo, more without turbo and it will fall right in without a clutch. I usually let the gears grind slightly by holding the shifter slightly against them while waiting for the RPMs to drop. If the stick is kind of grabbing the gears and throwing the stick back at your hand, the RPM is to low and if its just steady grinding, the RPM is too high. Takes a while to get that feel, but the governor trick is easy and works every time with the 2 stroke.