Using service brakes to simulate load

[Scott & Heather]

Is this detrimental if bus is equipped with an Allison auto tranny? While trying to get my coach up to temp on cooler days so I could burp air out my cooling system I didn't want to go through the process of unhooking sewer power water and then driving the coach on the road only to overheat and have to pull over to fill with more water/coolant. So I made sure nothing was in front of me and I used the ebrake and service brakes sometimes to simulate a slight load and gave it a little throttle until it reached the temp Tstats opened. Then I let her cool down and added more coolant. Just wondering if this is bad for the tranny long term.


Sent from my iPhone using Tapatalk. Clumsy fingers may contribute to mistakes.

[bevans6]

So I understand it, you're driving through the torque converter against locked brakes, yes?

Brian

[luvrbus]

It won't damage a Allison it's all part of the stall and heat test outlined by Allison in the book ,lock the brakes shift to 1st or reverse run it wide open find the stall speed on the converter then shift to neutral and preform the cool down test

[eagle19952]

which has time/duration limits/criteria..but I seriously doubt you approached them or the RPM (full throttle) needed to complete the tests

[Scott & Heather]

Yes Brian...exactly. In this instance it was impractical to actually unhook the coach, and pull it out onto the roads where it was overheating cause of air pockets in the cooling system, shutting down, and I was in the road. But I needed to get it up to operating temp and past the point of tstats opening to burp the air so I left the ebrake applied, had nothing in front of me (just in case) and applied a small amount of throttle until she warmed up past tstat opening temp. Then let her cool shut her down, and added more coolant. Worked like a charm, but wasn't sure if it was bad for the 740. And no, I was nowhere near wide open throttle and I only had to do this for a few minutes at a time.

[brmax]

As luvrbus mentioned it is a test in an Allison manual for purposes. Also briefly in a test situation for im sure every automatic made, vehicles, dozers, etc. Its been 5 years since I had a laptop programing close in hand but the available load test on engines and trans are a common thing as the pc test many solenoids and psi signals. And they make some weird noises in them test with some rockin, quite a site and feel your first few times in a cab.

[Iceni John]

What's the maximum temperature you should let it reach?   I have a temp gauge for my 740, but I don't know if it reads off the torque converter or off the transmission itself (bands, clutches, etc.).

John

[luvrbus]

250* is the max for short periods normal is 180* to 220*,it should read of the torque converter unless you have a sump sensor then it will read 10* lower