Why you don't want the Allison AT545 Transmission in the mountains.

[turf]

nice description!
the 2 descents of i-70 between the eishenhower tunnel and denver are also, completely butt puckering on a good day. its a moving traffic jam at 65mph, and if you run with traffic, you are careening out of control down the hill in 3rd gear at 85 mph. the trans sounds like its made of gravel and you hope it makes it down to the bottom without leaving pieces of it in a trail behind you.

been there, done that

now with the cooler, and some experience driving the grades, i feel safe going up or down the grades under 45. before the cooler i would be lucky to be running 15-20 by the time i got to the top. i highly recommend the trans cooler, its breathed new life into what i thought was a worn out transmission.

when i do grind up the 545, i'll get another!

 

[AlleyCat67]

I presume the second pass you mean is Vail, at 10,603 feet....

Been there, done that..... so know exactly what you mean... you think a 25k bus is bad, try it in an 80k big rig!

 

[Blubus]

Turf

I have the same drivedrain on a similarly sized transit bus. Can you share some info on the trans cooler solution you found for your at545??

I was wandering around the web reading up on direct transmission swaps for an at545 but if an aux trans cooler accomplishes what I'm looking to do, I could avoid a swap all together.

We won't be making any crazy hill climbs but will have extended periods of holding the same speed on a highway. A trans cooler would be an awesome way to keep the tranny in check without a locking torque converter! :Thanx:

nice description!
the 2 descents of i-70 between the eishenhower tunnel and denver are also, completely butt puckering on a good day. its a moving traffic jam at 65mph, and if you run with traffic, you are careening out of control down the hill in 3rd gear at 85 mph. the trans sounds like its made of gravel and you hope it makes it down to the bottom without leaving pieces of it in a trail behind you.

been there, done that

now with the cooler, and some experience driving the grades, i feel safe going up or down the grades under 45. before the cooler i would be lucky to be running 15-20 by the time i got to the top. i highly recommend the trans cooler, its breathed new life into what i thought was a worn out transmission.

when i do grind up the 545, i'll get another!

 

[turf]

here is my thread documenting my install of a used trans cooler.

http://www.skoolie.net/forums/f33/adding-a-transmission-cooler-to-my-at545-14363.html

IIRC, i'd just get jeg's largest cooler and add that on. my cooler is about 18"x18" with the electric fan tied to the fan clutch wiring. it helps a ton climbing the hills and highway driving. biggest bang for the buck upgrade i've made yet.

 

[Tango-SKO]

Roger the cooler, no matter the trans. The fluid dies fast at anything above 200 and the life of the trans goes down with it.

If you can keep it at/below 180 you can expect maximum life for both.

 

[EastCoastCB]

here is my thread documenting my install of a used trans cooler.

http://www.skoolie.net/forums/f33/adding-a-transmission-cooler-to-my-at545-14363.html

IIRC, i'd just get jeg's largest cooler and add that on. my cooler is about 18"x18" with the electric fan tied to the fan clutch wiring. it helps a ton climbing the hills and highway driving. biggest bang for the buck upgrade i've made yet.

So are you not running the other transmission?

 

[turf]

So are you not running the other transmission?

i'm still running the at1545. i destroyed the 545 when i removed it. i tried getting the speedo gear out the hard way and really buggered up the original 545, there was no going backwards

no way that new 1545 transmission is coming off again if i have anything to do with it. the cooler upgrade was before the the 1545 swap. and in hind sight, the swap was just for shits and giggles, as the original 545 was fine.

i did re-plumb the cooler with the transmission swap, running the new cooler first in line, and then to the original cooler to keep the temps up in the operating range.

 

[Jsneeb]

Wow, I learned a ton from this thread.

But can I ask what this horrible condition you described is of letting the bus accelerate downhill and exceed the appropriate speed for the gear?
Why is this bad?

As I think about it you would want to be in the lowest gear possible and trying to keep your engine RPMS as high as possible ( without exceeding the redline) for the benefit of the engine braking. Who cares how fast the transmission is spinning, it doesn't have pistons or valves that typically limit the RPMs of an engine.

I've only ever owned manual transmission vehicles, Only time I drive an auto is if I rent a car or if I have to drive one of my friends vehicles.

In my manual car I can get up to 80 MPH and put it in second gear if I want. Now if I release the clutch I'm ******* screwed, but there is nothing preventing me from putting the transmission into that gear. What is different about the auto?

 

[cadillackid]

Most autos wont drop down... they will deny the shift by hydraulic pressure... the governor in some autos if set just below the engine's max RPM will cause the trans to upshift on turbine speed or engine RPM regardless of the hear selector..



I know the AT545 and allison 1000 wont drop down to a lower Gear when you are going too fast for that gear...

-Christopher

 

[Booyah45828]

Wow, I learned a ton from this thread.

But can I ask what this horrible condition you described is of letting the bus accelerate downhill and exceed the appropriate speed for the gear?
Why is this bad?

As I think about it you would want to be in the lowest gear possible and trying to keep your engine RPMS as high as possible ( without exceeding the redline) for the benefit of the engine braking. Who cares how fast the transmission is spinning, it doesn't have pistons or valves that typically limit the RPMs of an engine.

I've only ever owned manual transmission vehicles, Only time I drive an auto is if I rent a car or if I have to drive one of my friends vehicles.

In my manual car I can get up to 80 MPH and put it in second gear if I want. Now if I release the clutch I'm ******* screwed, but there is nothing preventing me from putting the transmission into that gear. What is different about the auto?

It has to do with grade braking. The vanes in a torque converter are really only designed to flow fluid in one direction. Therefore when descending a grade, and the transmission is trying to drive the engine, it won't be doing it effectively due to the design.

A lockup torque converter provides this direct connection.

*on a side note. Please never put you transmission in 2nd gear while doing 80. Yes the clutch is pushed in and the engine may be at idle. But you're still spinning the clutch disc, which would be turning way faster then it was ever designed to turn, which can cause it to grenade. I've seen it first hand. If you have to coast, either do it in the respective gear for the mph, or do it in neutral.

 

[cadillackid]

It has to do with grade braking. The vanes in a torque converter are really only designed to flow fluid in one direction. Therefore when descending a grade, and the transmission is trying to drive the engine, it won't be doing it effectively due to the design.

A lockup torque converter provides this direct connection.

*on a side note. Please never put you transmission in 2nd gear while doing 80. Yes the clutch is pushed in and the engine may be at idle. But you're still spinning the clutch disc, which would be turning way faster then it was ever designed to turn, which can cause it to grenade. I've seen it first hand. If you have to coast, either do it in the respective gear for the mph, or do it in neutral.

ha!! i totally watched this first hand out jeeping a few years ago.. we were crawling some pretty steep stuff... everyone was in low range 1st gear creeping... we got to the top and there was a nice trail down into a valley.. I popped into 4H and 2nd gear.. the dude in front of me just put his clutch in and coasted down.... about halfway.. kablooey!!!!
-Christopher

 

[Fox Slider]

So if you drive it right in a 6 window fullsize shorty, Keep it under ? temp, fresh fluid/filter.. It will work? And ill put a big external cooler with fan on it.

I kinda wanna try it just to see how bad it is now. lol.

I wont be laughing stranded in BFE though. haha

 

[cadillackid]

On a 6 window on flat ground you’ll likely be fine with it

 

[Mr4btTahoe]

So if you drive it right in a 6 window fullsize shorty, Keep it under ? temp, fresh fluid/filter.. It will work? And ill put a big external cooler with fan on it.

I kinda wanna try it just to see how bad it is now. lol.

I wont be laughing stranded in BFE though. haha

It'll be ok if you drive it knowing it's limits. Stay off the steep grades and if you do have to run through the mountains, the uphill will be slow (25... 30... maybe slower).. on the downhill, the only thing that will be holding you back are your brakes (which will get hot easily/quickly).. no engine braking to speak up (it'll feel like the bus is in neutral almost)... so you best be going slow when you crest the hill. There are a few youtube videos showing rigs with 545s pulling and descending grades.



Plenty of people have driven buses with 545s all over.. keep it cool (under 220 for long periods.. under 200 preferred) and go. Get a quality temp gauge and cooler on it.


Obviously it isn't ideal... but it is doable.

 

[Mr4btTahoe]

 

[Mr4btTahoe]

https://www.skoolie.net/forums/f33/...-fe-5-9-cummins-and-545-alison-auto-8063.html


Here's a good rundown of how to operate the 545 in the hills.

 

[Fox Slider]

Right on. ya, i plan doing a downhill mtb trip in it next summer. So ima be in the hills.

Thats wild you gotta go that slow.

Ill research which trans swap is most reasonable and cost effective. Pretty much just have that in plan.

Or just find/buy a manual one and be better off.

hmmm...

 

[Mr4btTahoe]

Right on. ya, i plan doing a downhill mtb trip in it next summer. So ima be in the hills.

Thats wild you gotta go that slow.

Ill research which trans swap is most reasonable and cost effective. Pretty much just have that in plan.

Or just find/buy a manual one and be better off.

hmmm...

Does your bus have air brakes?

 

[EastCoastCB]

So if you drive it right in a 6 window fullsize shorty, Keep it under ? temp, fresh fluid/filter.. It will work? And ill put a big external cooler with fan on it.

I kinda wanna try it just to see how bad it is now. lol.

I wont be laughing stranded in BFE though. haha

I'd rather have my 545 than an emissions era money pit. 545's are cheap to replace.
In a shorty a 545 is hard to avoid.

 

[Fox Slider]

https://www.skoolie.net/forums/f33/...-fe-5-9-cummins-and-545-alison-auto-8063.html


Here's a good rundown of how to operate the 545 in the hills.

Thanks for that thread. That was good info!

ya im alrdy thinkn ill just a BIG cooler w/ elec fan on it.

So ya'll just manually shift it while driving. but say i put it in 2nd and go too fast it will shift itself into next gear? edit: nvm. answer was several post above