help, 2002 c5500 new to me

[deereborn]

2002 gmc c5500. Cat diesel, allison trans. I don't know much about this truck. Need help with 2 specific issues at moment.

1. parking brake system is not holding truck on steep incline, is there adjustment?

2. replacing rotted transmission cooler lines, changing out fluid, is there any band adjustment or reason to drop pan on this transmission? filter is spin on external.

[DmaxMaverick]

Welcome aboard!


2002 gmc c5500. Cat diesel, allison trans. I don't know much about this truck. Need help with 2 specific issues at moment.

1. parking brake system is not holding truck on steep incline, is there adjustment?

The parking brake is adjustable. Depending on why is isn't holding, it may need adjustment or repair. You'll need to get a closer look at its operation. If it's working, but just not working well, it will probably only need adjustment. Refer to the service manual for the check/adjust procedure.


2. replacing rotted transmission cooler lines, changing out fluid, is there any band adjustment or reason to drop pan on this transmission? filter is spin on external.Guessing it is a 2000 Series transmission, it has no bands, and no reason to drop the pan. The internal (traditional A/T filter) is only replaced at overhaul. Replacement of the lines, external filter and fluid should do it.

Check the owner's manual to be sure you are using the correct fluid. Castrol Transynd or other compatible TES-295 fluid is probably spec'd. You may also use name brand Dexron III, TES-295 compatible fluid. Do not use off-brand Dexron III fluid, if that is what is recommended. Use Castrol Transynd, if possible, to eliminate doubt.

[deereborn]

I bought 3 gallons of auto zone dex/merc III. I shouldn't use this? what is the difference really? Dex III is not a high tech or synthetic oil.

[DmaxMaverick]

I bought 3 gallons of auto zone dex/merc III. I shouldn't use this? what is the difference really? Dex III is not a high tech or synthetic oil.

I wouldn't use it. In 2006, GM stopped licensing and certifying Dexron III fluid. It was replaced with Dexron VI, with GM releasing a statement that it was fully backward-compatible. What that means to you and me is, there is no certifiable standard for Dexron III anymore, except for manual transmissions and gearboxes that spec. it. The upside to that is, every main, name brand ATF manufacturer has released statements saying their Dexron III fluid will continue to be no less compatible for auto tranny's than before the decertification. I don't know who supplies Auto Zone's fluids, and they change from time to time. This is a disqualifier, IMO. If you are using that truck at or near capacity, I recommend using Transynd, in any case. If you can't get it, let me know and I can suggest other fluids of equal quality. A transmission overhaul is well north of 2 grand, so I don't suggest skimping on the fluid.

[deereborn]

I will look for the transynd. What rpm should it shift at? Seems to shift really late to me. really have to get on the trottle

[DmaxMaverick]

What's the full powertrain, ratings, gear ratios, and curb and GV weights? Some of the late, smaller displacement Cat's run pretty tight, so it's hard to say. What RPM, under what load, do you consider "late"?

[deereborn]

cat 3126, allison at545n, 17000 gvw. empty or full load you basically have to floor it until it's up to the speed you want and then it will cruise at 2000 rpm, won't shift until like 2400, but seems to shift good, gets up to speed fast, but if you only go half way on pedal it will just sit there

[DmaxMaverick]

That sounds about right for a 26-30K GCWR truck (stock). If your loads are modest (24K or less), you can easily get away with upping the power and/or upping the gears and/or tires. Allison can then reprogram the TCM for optimal shifts. It's better to take it to them, tell them what you're haulin', and let them advise the optimum final drive and shift points. Optimizing the ratios will often boost economy, as well. If this is a motorcoach or an RV tractor, I'd certainly look into it.

[deereborn]

How do I turn up power, I notice one tag on motor says 350hp max, and then another one says it's set at 190hp max.