Shoving a 6V92 into a 6V71 hole

[Happycampersrus]

If you are going to use a 6v92, you can ALSO use the HT740 with no problem, but if you are using a 8v71 then the only auto that will fit is the MT644. Not alot of room on a MC5 to play with here. I don't have my books handy, but I believe the MT644 has an input rating around 275hp max.

With that said, My bus has a V730 with a 350hp 6v92 and has done fine for a couple of years with the extra HP, but I take good care on the way I drive.

HTH,
Dale

[TomC]

If you stay with 85 injectors, that will about duplicate the power of a 8V-71N that was at the top of the MT644 power rating.  Good Luck, TomC

[Tom Y]

Ray, Did you try USA parts at 1-800-USA-7899?  Used and new Allison parts.  Tom Y

[Tom Y]

Ray, Also I have a flex plate for a 6v92 to a 748 but I doubt if is the one you need. USA parts will know.  Tom Y

[Tom Y]

Check out this on Ebay #330066807448.  A 5C with a 6V92 and a 60 series world trans.  I think he means a 644, if so maybe it came this way.  Tom Y 

[TomC]

Personally-I'd use a DDEC 6V-92TA with a 3000MH (400hp and 1200lb/ft torque [more than the 6V-92TA can safely put out]) world transmission without PTO since it has the addition of two overdrives and is shorter than the HT740.  Good LUck, TomC

[belfert]

Personally-I'd use a DDEC 6V-92TA with a 3000MH (400hp and 1200lb/ft torque [more than the 6V-92TA can safely put out]) world transmission without PTO since it has the addition of two overdrives and is shorter than the HT740.  Good LUck, TomC

Isn't there a good chance the rear end ratio would need to be changed with a World Series tranny?  The two strokes run at a higher RPM than a 4 stroke and the overdrive might reduce the RPM of the 6V92 too much.  One option would be to have the 2nd overdrive disabled.  Also, I think a World Series tranny will require a DDEC III equipped engine, but I'm not sure on that.  DDEC II for sure.

On my Dina, I have a B500 and a Series 60.  With the rear end I have, the 2nd overdrive is disabled because Dina engineers claim the RPM of the Series 60 will drop too low.  (I kinda doubt their claim based on the RPMs I see unless the second overdrive is really aggressive.)  They told me straight out not to have the 2nd overdrive enabled when I asked.  (MCI hired two of the engineers from Mexico that designed the Dina coach.)

Brian Elfert

[TomC]

Cruise speed for a turbo 2 stroke should be between 1600 and 1800.  Cruise speed on an electronic 4 stroke should be 1400 to 1600 for best economy.

Brian- what rear end ratio do you have and what tires?  Most likely they don't want the 6th speed engaged since most bus drivers would drive the bus to fast.  The reality is that Allison designed the 6th speed to only go down to 1400 since they didn't like the transmission to be lugged in 6th.  So when the transmission gets to 1400 in 6th it will down shift to 5th.  The other gears can go down to 1100 at times of light pedal use.  Let me know your stats on your bus and I can tell you whether 6th should be activated.  Series 60 is good for lugging down to 1100.  The 2007 engines will be torque rated at 1100rpm, so they allow 100rpm below that.  So with the new 2007 engine, 1000rpm is all right!  Good Luck, TomC

[belfert]

Cruise speed for a turbo 2 stroke should be between 1600 and 1800.  Cruise speed on an electronic 4 stroke should be 1400 to 1600 for best economy.

Brian- what rear end ratio do you have and what tires?  Most likely they don't want the 6th speed engaged since most bus drivers would drive the bus to fast.  The reality is that Allison designed the 6th speed to only go down to 1400 since they didn't like the transmission to be lugged in 6th.  So when the transmission gets to 1400 in 6th it will down shift to 5th.  The other gears can go down to 1100 at times of light pedal use.  Let me know your stats on your bus and I can tell you whether 6th should be activated.  Series 60 is good for lugging down to 1100.  The 2007 engines will be torque rated at 1100rpm, so they allow 100rpm below that.  So with the new 2007 engine, 1000rpm is all right!  Good Luck, TomC

No idea what the rear end ratio is.  I'll try to find out Tuesday if I remember.

I doubt the engineers would lock out 6th to slow the bus down.  Much easier to do that in the DDEC.  My bus was speed governed and had some silly limit of how high the cruise could be set at.  I had the engine/tranny looked at at Detroit and I think they disabled the speed governer and increased the max on the cruise to 78 MPH.  I would like to get the Cruisepower stuff disable so I get the full 350 HP when not on cruise.

78 MPH is way faster than I care to drive a 36,000lb vehicle.  I have done a bit of 70MPH and the RPMs are at least 1650 at 70 MPH.  When driven at 65 to 68MH for long distances (800 miles on a tank) I have gotten as high as 9.1 MPG.

Brian Elfert

[Ray Powell]

I understand my 6V92T is 334 HP. I already had the MT644 so decided to use it. Gonna have the torque convertor increased to match HP. My truck mechanic wants to leave the turbo on top & I'll raise the cooling shelf couple inches. Where is a web site or listing on side mount turbo?
Thanks, C Ray

[TomC]

You can really mount the turbo anywhere.  In front of the engine (towards the back of the bus) would be good, then you wouldn't have to raise anything.  Good Luck, TomC

[Boise Belle]

My 1966 5A has had a MTB644 on its 8V71 for 12yrs.  I believe it is rated for max 55,000 lbs.  No problems, except no lockup in 1st and 2nd gears.   To remedy the lock up problem (which means the Jake Brake wouldn't work in 1st and 2nd), I installed a solynoid valve.   I can now manually lock up the torque convertor, when I want.  I got this Idea on this web site. Thank you to the gentleman who shared this info.  So now I can use my Jake Brake coming down a steep, winding, Idaho Mountain Road.  Don't know how common this is, but when I released the air from the air bags, the drive line would bind up on the axle, about a 1/2 inch before it would  rest on the bumpers.  I welded on a 1 inch piece of flat steel, to remedy this problem.  Note on cooling, not enough radiator for the stock 8V71, even when it had its original manual 4 speed.  But if you don't mind climbing a 7% grade when its 112 degrees out, at 28 mph, its a workhorse..  I have never had to pull over due to overheating.  And yes, my cooling system is in perfect condition.  Happy New Year.