is the AT545 THAT bad?

cadillackid · 03-26-2016, 08:33 PM

I see so much hate on the forums for the AT545... the bus I have my mark on has one in it... is it really that bad?? or do people just not like it?
-Christopher

gbstewart · 03-26-2016, 08:54 PM

I'm happy with mine, no problems so far , I would by an other one .
gbstewart

Robin97396 · 03-26-2016, 09:04 PM

There is a lot of hate for the 545, but there's also others that call it a workhorse. It's in a lot of equipment.

Are you familiar with the term "slush box"? You know, like when automatics first came out. Did you ever drive one of those? To me that's what the 545 feels like. It works and seems dependable so far. It's still quite the slush box and you have to floor it to get it to move. But like Cowlitz said these engins like being driven at that higher rpm's. My transmission shifts remarkably smoothly on the highways.
Apparently these will last pretty well if you maintain them properly. This will work until I get something better.

cadillackid · 03-26-2016, 09:32 PM

if the '545' is the transmission that "whistles" going from first to second.. then it seems to have been in every school bus I ever rode in as a kid / teen..

im not sure what my last bus had in it i never looked because it just worked.. but it had that sound... it was a 454 chevy in a 1988 bluebird..

I never knew a school bus was supposed to shift firm.. now the hotrod cars i built on the other hand I made them shift HARD...

I seem to be more in tune with the mechanics on this bus search.. perhaps too much... I never really thought about the last one other than I knew on a 454 I could mount 2 air conditioners easily and on the Diesel im likely to get i have no clue how to do such...

what is a good test drive test of the 545? im assuming the normal auto trans stuff? fluid;s red.. doesnt rev out of control in any gear? do you perform a stall test on a bus for 1st gear band slippage like with the old cars?

or is it simply just drive it, dont be crazy hard on it (like take it easy in the mountains?), enjoy it, and if it blows up build or buy another one?

the bus im likely to get is a short bus.. though it seems to have a high GVWR (27500) for a short bus.. but im thinking that the 545 is fine for a "short bus?"

-Christopher

EastCoastCB · 03-27-2016, 07:49 AM

My first bus had a 545. I didn't like it at all.
My second has the 643.

cadillackid · 03-27-2016, 08:01 AM

Quote:

Originally Posted by EastCoastCB

My first bus had a 545. I didn't like it at all.
My second has the 643.

didnt like it from what perspective? did it break? hunt shift in the hills? im mainly interested in reliability and longevity..

-Christopher

EastCoastCB · 03-27-2016, 08:27 AM

It just felt wrong, idk. Had to floor it to make it move. Shifts were hard and didn't feel right they felt forced. It did ok for the thirty mile return trip home but when I started bus shopping the next time I thought I'd go for a better drivetrain.
For actually traveling much, I don't think the 545 and gas engine were at all even a decent combo.

cadillackid · 03-27-2016, 08:50 AM

im thinking I had it in my last bus and it did seem like when I took off that i had to step hard.. but that was a 454 chevrolet gas engine and it seemed the stall speed was so low that the gas engine wasnt making power till the revs got up..

im going diesel on this one so maybe ill be bnetter off with the low stall speed because a diesel makes power at low RPM...

and its a short bus...

-Christropher

EastCoastCB · 03-27-2016, 09:33 AM

if its a shorter, lighter bus its probably much better. Mine was a 40' Thomas with a Ford 370 and the 545. I didn't like that bus so much when it came to driving it.
I was patient and knew what I was looking for this time around. DT466, 643 trans, AIR RIDE rear, 4.44 gearing.

2kool4skool · 03-27-2016, 09:43 AM

So far so good, we pull up to near 5000lbs often. The squeal is a feature of the 545, lets you know what gear you're in.

RE: AC mounting, our 5.9 has 2 compressors hanging low. To tighten/replace the belts I just lie on my back and there they are. Each has a separate belt.

EastCoastCB · 03-27-2016, 09:44 AM

I do remember that sound! ;)

cadillackid · 03-27-2016, 11:01 AM

Quote:

Originally Posted by 2kool4skool

So far so good, we pull up to near 5000lbs often. The squeal is a feature of the 545, lets you know what gear you're in.

RE: AC mounting, our 5.9 has 2 compressors hanging low. To tighten/replace the belts I just lie on my back and there they are. Each has a separate belt.

personally I always loved the 545 whistle... which pulley groove does the A/C run in? I wont know till I see the bus in person but looks Like I have 1 unused groove on the main damper pulley ... trying to find who makes that dual compressor bracket... single bracket kits are easy to find since all the trucks used the setup.. I dont think I'll have the capacity even if I run closed-loop evaporators and extra condensor along the skirt to cool a whole bus on one compressor... doing the design I cant make the numbers work the way I need them to.. well not and have a decent driver compartment cool-down.. in a 7 row a single unit rear high mounted will cool the passengers nicely.. a sanden 7 series will do that..

MAYBE I could run a small second coil.... but the design numbers are close doing that..

Tango · 03-27-2016, 11:56 AM

The 545 has been a solid workhorse for decades and when properly maintained can last for decades more. It was never a great tranny, but it was reliable. The fact that it only has four gears, no OD, shifts hard, lacks lockup and is renowned as a fuel guzzler make it a dinosaur these days when compared to the new gen Allisons.

Robin97396 · 03-27-2016, 12:18 PM

Mine shifts so smooth you probably wouldn't know it was shifting if you couldn't hear it.

What would the the top couple replacement transmissions for the 545?

I've heard of the 1545 with the lockup, but honestly I'd like more gears. This bus seems to be pretty good on the highway, but oddly enough I bought it for the logging roads here in Oregon. Go figure. I've got no low speed power. It gets up to highway speeds but takes off like a loaded semi. It's embarrassing on hills, even on the highway. I'd be in good shape if I lived in the great planes of the mid-west.

For those of us with 545s, what transmission or transmissions could we probably acquire over time that would basically bolt up in place of the 545?

cadillackid · 03-27-2016, 01:20 PM

these posts are great, sounds like exactly what im looking for ,i realize there are newer better things out there.. I have to learn with the original first then update.. im just glad to hear that it appears the 545 when taken care of will run a long time.. the advantage is its pretty cheap (in commercial vehicle speak) to rebuild if I bust it..

since I havent yet driven the bus I have picked out I dont know how it will act.. I still have the option of a different bus.. I just happen to like the industrial-interior feel of the older units.. as opposed to the car-like dashboards of the newer stuff... easier to take apart for repairs and custom updates too...

as far as more gears.. every bus i ever drove could use more gears it seemed.. I dont plan on doing anything crazy like turning the screw way up on the DT360 (though I have no idea if its been done).. my bus will drive on the freeway.. and ive been told it drives at 65 nicely... its a bus and im not a driver with 10s of 1000s of hours under my belt so to me 65 is as fast as I'll ever want to drive a bus...

some of the newer electronic transmissions look really nice and im sure I could build controllers for them like I did the 4L80-E I ran in my chevy hotrod car..

im glad to hear that the 545 doesnt seem to be the equivalent in the bus world to what the THM-Metric 200C was in the classic car world...
-Christopher

Booyah45828 · 03-27-2016, 09:41 PM

Like others have said, the 545 is alright. It's not a desirable option by any means but I wouldn't avoid it.
Those with shifting problems, I'd check your tv cable and make sure it's adjusted properly. Mine is on the throttle pedal but you might also find it on the side of the injection pump.
A large majority of the shifting issues I've seen in these old mechanical transmissions are related to fluid condition, TV cable adjustment, or mismatched applications after a swap.
You should be able to easily hear and feel it shift, but not so hard that it breaks your neck.

crazycal · 03-28-2016, 02:13 AM

Quote:

is the Herpes THAT bad?

I don't know. You tell me.

The non-lockup converter is enough of a deal breaker for me. Plus, in many applications, they are being used at their gross weight spec while the 643 is speced at double the maximum weight of any school bus.

turf · 03-28-2016, 03:04 AM

it doesnt take much of a reason to dislike a transmission. slipping, funny noises, and the lack of the lock up are all good reasons to dislike the the at545.

i looked hard at swapping my at545 to the mt643, but even with a free transmission,the labor to install one and fabricate the mounts is probably more than the bus is worth.

they are not a direct swap. the mt643 version has different cross members on the bus frame and fits differently. its not as easy as unbolting one and bolting up the other. likely the bell housings are also different.

when i toast my 545, i'll get a rebuilt one or a used low mileage one. if i was going to throw stupid money at the bus, i'd go after a low drive ratio rear end.

65 can be slow on an 80mph interstate, but on a 2 lane road with no shoulder and the sun in your eyes, 65 is as fast as i need to go.

EastCoastCB · 03-28-2016, 06:33 AM

I don't think I'd bother swapping out the 545. I just think if one is bus shopping, why not get the good stuff?

Tango · 03-28-2016, 09:12 AM

For anyone so interested...

FREE Allison AT545 Transmission

Came with my Cummins 4BTAA but has been replaced with a 6 speed. Was told it was operating fine when removed from the P30 it was originally in. Has driveline park brake.

Located in Houston, TX

PM me.

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