Mechanical engine - transmission combo

[BUDDY1976]

I have been shopping for a bus. I decided on getting an older mechanical engine (DT466, Cummins 8.3 or 5.9) not wanting a T444. And I decided to avoid the AT545 transmission. Manual would be my ultimate preference but have found none. I was told by a bus guy a few things that I am wanting to verify.
He said automatics with locking gears are overdrive transmissions and are electronic and will be paired with motors with electronic fuel injection.
So were there no locking gear transmissions like mt643 or md3060 paired with mechanical dt466, 5.9, or 8.3? Or no mechanical motor with automatic transmission with overdrive? Am I looking for something that doesn't exist? Is finding an old manual my only option for a mechanical motor and non at545?

[Ronnie]

Mt643 is a 4 speed non overdrive trans with a locking torque converter, and is often mated to the older mechanic engines you mentioned. It can also be used to replace the at545. Need to get all the right pieces but it can be done.

Much older (1970's) is the MT-40 6 speed. No over drive, but does have a locking torque converter. This is often found on gas engines. One heavy beast of a trans, just over 500lbs.

[Drew Bru]

Originally Posted by Ronnie

Mt643 is a 4 speed non overdrive trans with a locking torque converter, and is often mated to the older mechanic engines you mentioned.

Yup, that's our setup. MT643 with a DT466 mechanical.

[cadillackid]

mechanical engines are getting harder and harder to find.. IH started the DT466E in 95.. mechanicals made it in a few busses from 95-early 98..



the cummins 6BT was made up through the 97 model year i believe..



you can find them just getting more difficult ..

[EastCoastCB]

Originally Posted by BUDDY1976

I have been shopping for a bus. I decided on getting an older mechanical engine (DT466, Cummins 8.3 or 5.9) not wanting a T444. And I decided to avoid the AT545 transmission. Manual would be my ultimate preference but have found none. I was told by a bus guy a few things that I am wanting to verify.
He said automatics with locking gears are overdrive transmissions and are electronic and will be paired with motors with electronic fuel injection.
So were there no locking gear transmissions like mt643 or md3060 paired with mechanical dt466, 5.9, or 8.3? Or no mechanical motor with automatic transmission with overdrive? Am I looking for something that doesn't exist? Is finding an old manual my only option for a mechanical motor and non at545?

There are mechanical engines paired to 3060's. Other than that your best bet is a 643 and gear it right.

[BUDDY1976]

Originally Posted by EastCoastCB

There are mechanical engines paired to 3060's. Other than that your best bet is a 643 and gear it right.

Do you mean "gear it right" with the rear end?

[Form&function]

I swapped for a 8.3 and 653. There is hardly a wire on the whole deal and is very reliable. They mated the old p-pump diesels to several non electric transmissions,643,653. You can find them in city trucks,dump trucks and military 5 tons.

[EastCoastCB]

Originally Posted by BUDDY1976

Do you mean "gear it right" with the rear end?

precisely.

[cadillackid]

the 653 is nice if you need a granny gear.. which most of the manuals give you.. as mentioned a lot of mechanical engines matyed to 643 or 653.. ive seen the 653's in trash truck setups ..

[Form&function]

Yep,some kids tossed a match in a parked trash truck and burnt the back half to death. I ended up with the engine pretty cheap. Back a few years ago you could just part out a 5ton military truck for pennies on the dollar. Last one I bought was like 3k and had 14,000 miles. They're all sold off these days though.

[BUDDY1976]

Thank you for the feedback. I will keep searching. So many AT545s...

[Booyah45828]

To summarize.

Most of your mechanical engines were phased out in the mid 90's

The MD3060 is an electronic transmission, with it's final drive being an OD ratio, and a locking torque converter clutch. This transmission was introduced in the early/mid 90's.

The MT series allisons (mt643, mt653, mt654, etc.) are a mechanical transmission, with it's final drive being a direct drive ratio, and a locking torque converter clutch. This transmission was introduced in the early 70's and was phased out in the late 90's/early 2000's.

The AT series allisons (at540,at545, etc.) are a mechanical transmission, with it's final drive being a direct drive ratio, and no locking torque converter clutch(except on the at1545). This transmission was introduced in the early 70's and was also phased out in the late 90's/early 2000's.

With all that said, it was possible in the mid 90's to buy a bus with a mechanical engine coupled with the md3060. It was a rare option back then, and finding one of those now has only gotten rarer because they would currently be 20+ years old, and would likely no longer be owned by a school district.

That would be a perfect bus in some people's eyes, because it has the simplicity of a mechanical engine, coupled with the highway cruisability of a transmission with a OD gearing.

As ECCB said, you can also achieve highway cruisability by running an mt643, with a numerically lower rear end ratio. But doing so can hurt your acceleration performance, so with the 4 speeds, one must compromise between top speed and acceleration.

[EastCoastCB]

I'd also add that if you're looking for a short bus its real hard to avoid the 545. If the bus is nice the 545 can be upgraded later on. Or one can add a cooler and run transynd to try and get the most out of a 545.

Just had to add this in as pre-2004 shorties without 545's are rare.

[BUDDY1976]

@Booyah45828 thanks for all the helpful information. Did the 90s manual transmissions have no overdrive?

[EastCoastCB]

They're usually spicer 5 speeds with granny low and 1:1 top gear. So for actual day to day driving they're 4 speeds with no od.

[Ronnie]

Originally Posted by EastCoastCB

They're usually spicer 5 speeds with granny low and 1:1 top gear. So for actual day to day driving they're 4 speeds with no od.

Yes the same on mine, 5 speed, granny low, so driven as a 4 speed. No overdrive

[Booyah45828]

The later ones would have more likely been the spicer 6+1. Similar to the 5 speed eccb and ronnie alluded to, but this one uses 6 gears normally, and the +1 indicates a granny low that's rarely used, so it's actually a 7 speed.

Most of the time with the 6+1, 7th is a direct gear, but some of them had an overdrive. You'll have to look at the transmission data plate and get the model number to be sure.

[Booyah45828]

Usually with the model# on the data plates, if it has an O in or after the letters, that normally indicates overdrive.

So an eaton example would be ES56-7 would be a direct, whereas an ESO66-7 would have an OD. A fuller example would be FS-6406 being direct, FSO-6406 is an OD.

[cactusboob]

Originally Posted by EastCoastCB

I'd also add that if you're looking for a short bus its real hard to avoid the 545. If the bus is nice the 545 can be upgraded later on. Or one can add a cooler and run transynd to try and get the most out of a 545.

Just had to add this in as pre-2004 shorties without 545's are rare.

Whats transynd?

[EastCoastCB]

Originally Posted by cactusboob

Whats transynd?

Allison's own brand of synthetic transmission fluid. Its TES-295 rating is what to look for. Any brand of tes 295 trans fluid is the good stuff.