Non-Tow/Haul Downshift

[Tsckey]

This topic must have come up before, but I don't recall ever seeing it. I have noticed that when driving in the mountains with the transmission in the standard mode (non-tow/haul) it will nevertheless downshift occassionally to help supply engine braking to assist the speed retarding efforts of the brakes in the twisting sections or on long grades. This is not just a downshift for proper gear selection, but an accelerator blipping downshift. It surprised me at first, but I quickly got used to it. The downshifts were coming at the right time, usually decelerating into corners, and the tranny would hold the gear accelerating out of the corners long enough so that in the tight sections the trans would not shift up and down, but would stay in the correct gear from corner to corner. The shift pattern is not as aggressive as in the T/H mode, but correct for the conditions. Pretty neat.

TC

[mdrag]

Tsckey,

Check out the post on grade braking by Kennedy about 1/3 - 1/2 down the page:

http://forum.62-65-dieselpage.com/ubb/ultimatebb.php?ubb=get_topic&f=3&t=004239

Should answer all questions :D

[Tsckey]

Mdrag,
Got it. Thanks. I had thought the grade-braking feature was a tow/haul exclusive. John's post supplies the answer.

I notice you have installed Velvet Rides. Did they help the ride any? I know the duallies are going to be stiffer than my 2500, but something to take the kidney punching out of expansion joint freeway driving would be nice.

TC

[IndigoDually]

Check out http://www.allisontransmission.com/service/faq/#93

This site answers a lot of questions regarding our transmissions.

John

[mdrag]

Tsckey,

I have the Velvet Rides on my '01 3500 CC - they do make a small improvement, but I'm not sure it is enough to justify the expense - and they were quite a challenge to install. The rear top shackle bolt would not clear a rivet head on the top of the frame - no matter what I tried. I ended up having to cut off the upper shackle bolt on both sides to install the VR...Also, the receiver will need to be lowered to do this job - not that big of a deal, but it may be more of a job than bargained for...
The problem on the 3500's is the VR shackles bring the OL springs really close to the factory frame contact pads, especially at the rear - and once the OL springs hit the contact pads -> no more benefit to the VR shackles. My OL springs were within 1/2" or less of hitting the frame contact pads after the VR install. I removed the rear contact pads for a month or two, and the ride was much better. Unfortunately, the contact pads cannot be lowered easily...

500+ lbs of weight in the bed does the most for the harsh ride... The rear Bilsteins seem to help some as well...

Try a search for Velvet Rides in the 2500HD/3500 HJD Trucks and Drivetrain forum, there are plenty of posts/opinions on this topic.

mdrag