I discovered that 2nd gear lockup feature quite by accident while driving in the mountains. I noticed trans temp rising on long, slow grades running around 30-40mph. Dropping to 2nd cured it, and that's when I noticed lockup engaging like you said, somewhere just under 30mph.

There have been pump failures and belt problems/alignment issues. Just anecdotal. May be nothing, but I have seen a few posts over the past couple years with those complaints.

 

my 99 has hydroboost brakes as well, the only thing vacuum runs is the 4x4 actuator, a/c blend doors and cruise.
mine is always on as well, and if you slow down early enough, i don't even touch the brakes except to bring it to a complete stop. mine's a stick, so i can drop a gear anytime to keep it braking harder.

 

The vac pump on my 07' just took a dump last weekend, made a terrible noise. Took the belt off and ran a stock belt by-passing the pump. Prices on new pumps, unbelievable. Dodge dealer wanted $1046, Cummins (2 blks. away) wanted $215. I had hoped for it to last longer than 75K. But from what I've read some people have had to replace them multiply times, some others have gone a long time between replacements.

 

i'd really like one for my 'o1 what'll be the best banks, jacobs, BD?..... cost efectiveness is good to

 

I got a BD on the mystery truck and it works awesome I can bring that thing dam near to a dead stop from 70MPH with out touching the brakes

the one on the 08 is factory and seems to work flawlessly thus far (46,000)

 

So what good is having a 5" exhaust when you have a 3" Jacobs elbow?

 

On an automatic does the exhaust brake only work if you have a lock up torque converter? I don't think my allison 545 has one. hate to waste the money.