Bus for the Mountains: 35' RE Cummins 5.9 w Allison MT643

[s2mikon]

On both of the mt and ht series there is a solenoid valve that is installed to apply lock up upon application of jake or exhaust brake. It was the same part that was used to apply lock up for pto use. Otherwise like was mentioned in post 20 it just freewheels so to speak.

 

[Booyah45828]

I've seen that external solenoid and line on the HT's, never on an MT. I imagine it could work much the same so long as the valve body allows it.

Would be a necessary addition IMO if you are going with an exhaust brake on one. Be sure to tap the B+ line into the harness after the idle validation switch. You don't want to be stopped by this being engaged because of the switch on the dash.

 

[Bjorkinman]

8.3 engine brake

I’m converting my 40ft bluebird 6ct 8.3 Cummins and I’m in the rabbit hole of finding an additional braking solution. I see on the Cummins website https://quickserve.cummins.com/info/qsol/products/newparts/jacobs_md_nondodge.html
There looks to be an engine brake, but I have no idea what’s involved in the install and function. I have an md3060 transmission at least.

 

[s2mikon]

That is an exhaust brake. It works by closing a butterfly valve in the exhaust manifold. It is only as effective as your exhaust valve springs. I think it is around 200 negative horsepower when everything is working properly and at 2000 rpm. The transmission also has to lock the torque converter when it is engaged or it is useless. Will it help? Better than nothing. I have an exhaust brake on my 1 ton manual transmission truck and it helps but it is not anything like a real engine brake or a transmission retarder.