Allison grade brake - does it do anything for climbing?

Discussion in 'General RVing' started by mountainRVdude, Aug 4, 2006.

  1. mountainRVdude

    mountainRVdude New Member

    I just purchased a 37' 2006 Southwind with the 8.1L / Allison 5 spd workhorse package. Apparently the chassis is a 2005, hence the 5 spd. We live in the mountains above San Bernardino and pull an enclosed motorcycle trailer behind. Does the Grade Brake lock the torque converter to assist during those downhill runs and would that be of any assistance during a very steep 1st gear climb? We recently made a trip up a hellacious road called 9 mile road where we climbed to 8300 feet. I'm looking to do anything that I can to aid the MH during climbs like this, even the normal climb heading home. This is my first posting so if I posted in the wrong place, sorry. let me know. I just cannot find any doc that I can understand on this trans, which performed wonderfully during my initial outing.
    Thx. John
     
  2. Grandview Trailer Sa

    Grandview Trailer Sa Senior Member

    Re: Allison grade brake - does it do anything for climbing?

    Hello John and welcome to the forum. There are motorhome areas, but this the General Page, and you are fine. I have had this transmission in 4 trucks, the 2 five speeds I just traded and the 2 six speeds I have now. If you have the tow/haul button in your motorhome, it will change the shift points on acceleration. Usually it raised the rpm level before the next shift. That should help you going uphill. The Grade Brake is another feature of the trans.
     
  3. dbarton291

    dbarton291 Senior Member

    Re: Allison grade brake - does it do anything for climbing?

    Grade braking is a shift point function. It's a neat feature used to help control downhill speeds. It is not an assist for uphill climbing. It is for the most part, independent of torque converter clutch operation. Workhorse has a writeup on grade braking on their website. Go to www.workhorse.com and search on grade braking. Here's one of the writeups at www.allisontransmission.com": It's called automatic grade braking at Allison's website, because that feature is always on in the GM HD pickup trucks that are built with the optional 1000 Allison.

    Q. Automatic Grade Braking - How does it work?
    A. The grade-braking feature's primary purpose is to utilize engine braking to slow a heavy vehicle on steep grades in order to reduce wear on the traditional braking system. The method used to slow the vehicle is by overriding the PRNDL position, effectively pre-selecting the next lower gear range automatically. Because the transmission is electronically controlled and there is no mechanical linkage that needs to be moved for a pre-select downshift, implementation of this feature can be done completely in software with no hardware modifications.

    This control feature takes into consideration several factors before commanding a pre-select downshift. These are the primary inputs to the Transmission Control Module (TCM):
    # Throttle position
    # (Service) Brake state
    # Vehicle acceleration/deceleration
    # Grade/Load
    # Vehicle speed

    These factors are continually calculated to determine when a preselect downshift is commanded.
     
  4. mountainRVdude

    mountainRVdude New Member

    Re: Allison grade brake - does it do anything for climbing?

    Thanks for the feedback gentlemen. I have had positive experiences with the Grade Brake heading downhill and was basically wondering if engaging/locking the torque converter would happen with this engaged. Apparently not.
    I was also checking into USGEAR and Gear Vendors underdrive for my unit but so far I have heard back from USGear and they have no application for a 5 speed Allison. I am suspecting that when Gear Vendors returns my call,
    I will hear the same thing. So as an aid for these extra steep first gear hills, I am now looking into the full Banks kit to kick up the HP and Rear wheel torque. Does anyone have any comments regarding this direction? This motorhome
    is my first "keeper" ( I hope to hang onto it for at least several years anyway ), so I'd like to get it setup to handle these sort of grades ( mostly uphill are the concern ). I started out looking at a pusher but opted out for more coach
    for the wife and had high hopes that the 8.1L / Allison workhorse would cover the gap. Not quite sure that I made the best choice right now, although the wife loves her coach and when she is happy.... well, you know...
     
  5. dbarton291

    dbarton291 Senior Member

    Re: Allison grade brake - does it do anything for climbing?

    I know. Happy wife, happy life.
    The problem climbing hills is not whether or not the torque converter clutch is engaged. It is a basic power/weight issue. My VERY strong recommendation is to not use the Banks on any vehicle equipped with the Allison 1000. The clutch control algorithms in the TCM (transmission control module) used for adaptive control (shift quality) are based on known input power levels. The use of aftermarket systems to boost engine power levels many times results in a failed C1 clutch.

    I forgot to mention Grandview is right about the tow/haul mode. If you have that, it does raise the upshift points to help some in going up hills. You can also preselect. That does not hurt an Allison. Of course if you're already in first gear, you can't preselect any lower.

    Here's another free personal opinion. City buses in the 35 to 40 foot length category are always powered by heavy duty diesel engines and those even struggle up some hills. If I were to purchase a vehicle that size, it would certainly be a Cummins or a Cat. However, they cost big. If your 8.1 goes adequately, the wife likes it, it doesn't have a bunch of problems, and the extra cost for the big bore diesel is prohibitive, well maybe that's the right vehicle for now.
     

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