Hi all,
Wifey and I just returned from a 1500 mile trip to Florida, and everything ran like a top. I got 6.75 MPG, and ran between 65-68 MPH from our home here in the Outer Banks to the gulf coast. I have the 8844 Spicer transmission, and while it ran fine once I got it adjusted, it seems to be slipping a bit, and quite frankly is not really enjoyable for me to drive. After doing a little head scratching, I'm in the investigative stages of switching out the Spicer for an Allison HT740 automatic. Here's my current setup:
8V-71, naturally aspirated, mechanical injection. It currently has the Spicer bolted to it. My thinking (and that's why I'm asking) is that the 740 would be pretty much a direct bolt-on replacement for the Spicer. Is that correct?
I'm curious how the transmission knows the throttle position. I'm assuming a cable, right? How does that work?
Second concern is the driveshaft. Will I need a new one, or are the two transmissions comparable in length?
Third thing is a shifter unit. Is there a good source for these?
Thanks in advance for any assistance. I'm just beginning my research, and I've been through the archives. It looks like others have done this. I'm just looking for some details. Thanks!
The modulator and governor tells the transmission when to shift Jason has a setup for sale in the spare tire section here a good price too
Thanks very much for the tip Clifford. I've sent him an email.
Do you have a "T" drive configuration? You might also consider the smaller 640 series of Allision configured for the 8V71N. That might save some bucks ... or might not.
Also ... and I am not sure here, would a proper 6 speed New World Allison with two, (2) overdrives also work? Can a electronical tranny be mated to a MUI Detroit? $How$?
I think, (not sure) the New Worlds are shorter even yet and might help with U joint angularity? That plus the overdrives might correct slow road speed considerations.
HB of CJ (old coot)
Had the MC7, with the 8V-71, 8844 trans, when swapped to the RTO910, ran into an issue, the Greyhound setup uses the SAE 1 Bolt pattern bell housing, BUT has the SAE 2 flywheel. Just a note you might want to check it out before you get going.
The easy method for me to check is the flywheel housing, if the hump for the starter is small, that would indicate the SAE 1 housing with the SAE 2 flywheel, however if the hump is large, then it is both SAE 1.
Unknown by me what the MC9 had, but Greyhound stayed pretty much standard setup for quick changing engines/drive setups.
Would be interesting to know.
In my case, I used a SAE 2 flywheel for the two disk clutch, then changed the RTO from the SAE 1 nose to the SAE 2 ande used a spacer from MACK to reduce the SAE1 bell housing pattern to the SAE 2 for the transmission, worked great for long time. The existing bell housing is too thin to use a SAE 1 transmission mount, why the spacing with the adapter from Mack.
If you could post a picture just thru the side door of the starter, showing the motor mount etc would be great.
In the end, you will be very happy with anything other than that 8844 box.
Dave M
Thanks for the answers and things to think about fellas. I'll shoot a picture of the starter tomorrow and let you take a look if you don't mind Dave. No matter what I end up doing, I'm going to want to know that information.
My thoughts this evening are that I don't really need to open this particular can of worms right now. I'm still in the conversion process, and I have less than 2 years before retirement. I'll have much more time to do a good job and get things right if I'm not pressured by work and the conversion process like I am now. I'm absolutely going to make the switch, but I'm thinking I'll just hang onto the Spicer until I have more time to fool with it. It'll also give me more time to look at all of my options and select what's best for my situation. Thanks for the good information guys. For now, I'll just dance with the one that brung me. ;D
Just curious what it would cost to convert a standard to auto on a bus like yours? Labor/parts?
Glen,if he shops smart like buying Jason's 740 for 800 bucks and can do his own work he can be around 3 grand or less if he hires it out to a shop look for 8 to 10 grand The MCI 9 is fairly easy
Thanks Cliff for the info. Always wondered what the cost of something like that would be. Have 755 cr in mine and that thing is a dream. Hope he gets it done and reasonable if there is such a thing with these puppies.
If I were facing the same issue again, I would just replace the bell housing with a proper SAE #1, that way the rest falls in place very simple, IF THE CURRENT BELL HOUSING IS THE ODD BALL.
Might like changing from the 3.73 rear to the 3.36, the 37 tooth ring gear is the tuff one, so changing from the 10 tooth pinion to the 11 tooth gear set makes a nice ratio, not a big need, but seems most make that change.
I stayed 3.73, used the RTO910 for gear choice, am a gear head I think.
Dave M
When I converted my truck from the RTO-14613A (13spd) to HT740, it cost about $11,000. I looked into the World transmission since it has the additional 2 overdrives (1-4gears are just about identical ratios). It would cost right at double the cost. With my 3.55 rears and 11R-24.5, I have a nice cruise speed of about 56 at 1,600rpm, 65 at 1850rpm-so I chose the HT740. Quite possibly the most reliable big transmission ever made. Just had to add the cable of the shift modulator to the throttle linkage. I don't think the HT740 will work with the 8V-71 on the MC5-it will be too long. Why not just change the whole thing to a 6V-92TA with the HT740-then you'll have some power and better fuel mileage.
As to using the World transmission with an mechanical engine-you just need a cable operated electronic gas pedal positioner sensor for the fuel modulator. But-as said before, it will be expensive! Good Luck, TomC