1990 GMC shorty advice

[Brdfrd]

I found a 1990 Bluebird GMC shorty, and I’m trying to figure out what transmission it has—same old question, right?

Owner says it has an 8.2L V8 Detroit Diesel with Allison 3 speed automatic, hydraulic brakes, 194k miles.

I doubt is has a 3 speed, he sent a photo of the shift selector—is this an MT643?

The photo is pretty lousy, but maybe it helps?



Thanks in advance, Brad

[EastCoastCB]

Almost surely its a 545. Could be a 643. To truly know you'll need to look at the transmission itself. The shifter is the same for both.

[Brdfrd]

Thanks, I figured it was probably one or the other. Too bad, it’s a pretty clean looking bus.

[Jordan_addis]

Hey just curious as I’m beginning to look into a purchase too, What’s the downfall of either of these transmissions?

[Ronnie]

The AT 545 is a 4 speed without overdrive, and does not have a lockup torque converter. Works well for a route bus, but on long trips no lock up on the torque converter makes lots of heat, and long grades may require stops to let it cool down.



The MT 643 is also a 4 speed without overdrive, but it does have a lockup torque converter.

[Brdfrd]

Bailing on this bus, but have a second question:

I want to be able to do all/most of my own maintenance/repairs/upgrades. I lknow newer busses have complicated emissions systems and electronics that are not typically user serviceable. I assume there is a year where just about everything switched over to these systems due to regulatory changes. Does anyone know what year that might have been?

I have a vague idea that it’ was around 2000-ish, but it would save a lot of time searching, if I knew to exclude anything 20XX or newer.

Thanks!

[EastCoastCB]

Originally Posted by Brdfrd

Bailing on this bus, but have a second question:

I want to be able to do all/most of my own maintenance/repairs/upgrades. I lknow newer busses have complicated emissions systems and electronics that are not typically user serviceable. I assume there is a year where just about everything switched over to these systems due to regulatory changes. Does anyone know what year that might have been?

I have a vague idea that it’ was around 2000-ish, but it would save a lot of time searching, if I knew to exclude anything 20XX or newer.

Thanks!

I avoid anything 2004 and newer. To me the late 90's is the sweet spot.

[Ronnie]

Any bus with an engine that has an "E" after the numbers, like DT466E is an electronically controlled engine. The mechanical ones would be as an example DT466.