Advice on use of BD exhaust brake on slow grades

[Crowhurst]

I'm learning how to use my newly fitted BD exhaust brake, and I would be grateful for some advice from experienced users. The Autolock unlocks the torque converter lock-up clutch on decelleration at 28mph, so the exhaust brake has virtually no effect from that point. I assume therefore that on descending a long grade, overdrive off, with a heavy load and a 6500 pound trailer, if there is a sharp bend, perhaps, and my speed drops below 28 mph, I will have to rely on my service brakes for the rest of the descent? This happened yesterday. I tried to speed up a bit to re-lock the TC clutch, but chickened out after a while! My home is at the top of a grade, with bends, so this is relevant to me. I could change into second gear, but the TC will not lock in second, and the exhaust brake will not work, although engine braking would be improved. (and the tansmission fluid will get hot? I have a temp gauge on the transmission output line). Is there a way round this, or should I have bought a stick shift? Thanks. Nick.

 

[Joe G.]

A DTT valve body will allow TCC lockup in 2nd. Mine works great on slow steep crooked grades.

 

[emjay]

To be fair, most aftermarket transmission builders offer 2nd and some even 1st gear TCC lockup capability. The exhaust brake is best accompanied by an aftermarket torque converter as well.

 

[Mschevey]

Don't run the e-brake without some kind of lockup device. It will cook your transmission in very short order.



There are a number of aftermarket ways to lock-up the converter.



Mike

 

[illflem]

I don't know that it will cook your transmission without lock-up, think it just won't slow you down.

 

[Blair]

The TC cutout speed is programmable via the Switches inside the Autoloc box, and you can set it for any speed you want. The one thing you don't want is your RPMs to drop below 1,000 before the TC releases.

 

[Crowhurst]

Thank you all for that information. Before posting this thread I rang the BD technical help line for advice. The polite and helpful gent told me that the brake was not supposed to help in the circumstances which concerned me, that the brake was for highway speeds, and I shouldn't expect it to replace my brakes. When I said I would then have to use 2nd gear to give me engine braking, he was concerned that this would overheat the transmission fluid. I am still uncertain about this. My owner's manual, page 120, recommends the use of 1st and 2nd gears for up and down long grades, and for city traffic. The TC clutch would be unlocked, but I would keep the transmission temperature on the hot output line below 200 degrees. I would appreciate further guidance on this. In the short term, I will establish the speed equivalent of 1000 rpm in 3rd gear, and phone BD for the dip switch settings. In the longer term, it looks as if I need to save up for a valve body with at least 2nd gear lock-up. Thanks again. The TDR is a great system. Nick.

 

[emjay]

The main cause of trans fluid heating is driving with the tcc unlocked. If the TCC is locked, running the exhaust brake will not cause the fluid to heat up. On the other hand, if the TCC is unlocked, the exhaust brake will be largely ineffective.