I took the plunge.... Now I have questions

[Aviator]

Hi All

So Here's what I know and don't know

I Ran the bus up on blocks and blocked it up, and three of us looked for the data plate. We all agree, we see where it should be but there's nothing there

I reached out to the company I bought it from and they are pulling records to see if they have any notes on what trans is in it.  When I bought it, the gave me all the maintenance records from the day they bought it but no mention of what transmission it is.

As an aside, Its hilarious to read the mechanics comments about the drivers.  Its a comedy show waiting to happen

Back to the bus   Here's what I get from at road test  . I haven't gotten the bus out to my hangar yet to verify the tach so these are the numbers that come up on the tach but nit verified yet.

Idle 800 RPM

Selector in D  From a standing start
Shift at 10 MPH 2500 to 1500 RPM   Short Shift (lockup) at 8 MPH 2500 RPM to 2000 RPM
Shift at 20 MPH 2500 to 1500 RPM   Short Shift (lockup) at 16 MPH 2500 to 2000 RPM
Shift at 31 MPH 2500 to 1500 RPM
Shift at 41 MPH 2500 to 1500 RPM  This shift is kinda hard
Bus winds out to 63 MPH at 2750 RPM

If I put the selector in 1
Short Shift (lockup) at 8 MPH 2500 RPM to 2000 RPM  Bust tops out at 13 MPH 2700 RPM

If I put the selector in 2
Shift at 10 MPH 2500 to 1500 RPM   Short Shift (lockup) at 8 MPH 2500 RPM to 2000 RPM
Short Shift (lockup) at 16 MPH 2500 to 2000 RPM Bus tops out at 23 MPH at 2700 RPM

If I put the selector in 3
Shift at 10 MPH 2500 to 1500 RPM   Short Shift (lockup) at 8 MPH 2500 RPM to 2000 RPM
Shift at 20 MPH 2500 to 1500 RPM   Short Shift (lockup) at 16 MPH 2500 to 2000 RPM
Bus tops out at 35 MPH at 2700 RPM

Below is a picture of the ATEC Box located in Bay 3 Drivers side

Does any of this ring a bell with anyone or should I just head off to an Allison shop and have them figgure out whats in the beast?

Larry

[Aviator]

One more thing,  I googled all of the numbers on the ATEC box and came up with squat

Larry

[luvrbus]

You have 700 series sounds like unless someone has locked out 5 and 6th on a World Transmission and using the generation 1 pad even at that the World is 1:1 in 4th

[chessie4905]

   You could jack one set of duals off the ground just enough to rotate. Put a mark on bottom of sidewall. Trans in nuetral, engine off, brakes off, other wheels blocked. Get under to the driveshaft and put a mark on it. (SAFELY) Have someone rotate dual assy slowly exactly 2 turns, while you are counting turns of driveshaft. Repeat for verification. You'll have to estimate the final part of a turn. Then we'll all know what axle ratio you have

[Aviator]

Chessie

I'm hoping to avoid having to go that route, I'm hoping the maintenance department at the previous owner can shed some light on the situation

Its been said up thread and my dad agrees that it seems like its not doing something correctly after its shifts to third and fourth. Is there supposed to be a lockup in third and / or 4th?

I managed to troubleshoot the tach  (I'll start a new thread for that) and now it reading correctly for the engine.

So with the fixed tach here's what its really doing and shifting at

Idle 725 RPM  Fast Idle is 975 RPM

Selector in D  From a standing start
Shift at 13-15 MPH 2300 to 1500 RPM   Short Shift (lockup) at 9-10 MPH 2300 RPM to 1900 RPM
Shift at 22 MPH 2300 to 1600 RPM   Short Shift (lockup) at 16-18 MPH 2300 to 2000 RPM
Shift at 33 MPH 2300 to 1500 RPM   The shift is on the hard side
Shift at 43 MPH 2300 to 1500 RPM  This shift is also kinda hard
Bus winds out to 63 MPH at 2300 RPM

If I put the selector in 1
Short Shift (lockup) at 10 MPH 2300 RPM to 1900 RPM  Bust tops out at 15 MPH 2300 RPM

If I put the selector in 2
Shift at 14 MPH 2300 to 1500 RPM   Short Shift (lockup) at 9-10 MPH 2300 RPM to 1900 RPM
Short Shift (lockup) at 16 MPH 2300 to 2000 RPM Bus tops out at 23 MPH at 2300 RPM

If I put the selector in 3
Shift at 14 MPH 2300 to 1500 RPM   Short Shift (lockup) at 9-10 MPH 2300 RPM to 1900 RPM
Shift at 20 MPH 2500 to 1500 RPM   Short Shift (lockup) at 16 MPH 2300 to 1900 RPM
Bus tops out at 36 MPH at 2300 RPM

55 MPH looks like 2000 RPM on the tach

Thoughts?

Larry

[chessie4905]

   I would make sure trans fluid isn't low when hot. Also give the computer numbers to an Allison servicing dealer. They will be able to help. Regardless, it would be good to know final drive ratio. Who knows... maybe it has 5:20 or 4:88 rear.

[hargreaves]

With an HT740 or 748 at 2250 rpm 22.5 tires your maximum speed in high gear will be approx. 63 MPH with 4.10 gears.

Cheers Gerry

[Seangie]

Larry -

I am with Gerry and Chessie on this one.  I don't think there is anything wrong, I'd assume that the gear ratio is what is keeping you from hitting speeds higher than 63.

-Sean

[luvrbus]

A 410 is a good gear for the L-10 Cummins

[chessie4905]

4.10 with 12:00x22.5 at 2250 with direct high gear should be 68 or 69 mph.

[luvrbus]

He saying 2500 rpm

[Aviator]

Luvrbus

After chasing bad grounds  I'm now getting 2300 on the tach and that matches with the engine revs stated in the Cummins manual

I think you and Gerry and Chessie have hit on it, its a 4:10 Rear end and that 63 mph is just it

The bus originally had a 5 speed manual when it was built (it still has the old shift pattern plate)

I'll check the tires on Monday but I'm pretty sure they're 12x22.5

Larry