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rednlh · 06-05-2007, 05:59 AM

I have a 2002 Dolphin on a workhorse chassis with a 8.1 gas engine and a 1000 allison translmission. When I first started going to the mountains, I was not using the breaks a lot to slow down when I went downhill. I was told to have the engine and transmission reflashed by workhorse due to transmission downshifting. On the next trip to the mountions, I had to use the breaks a lot and they were getting very hot. It seams like the engine wasn't slowing me down. Since I don't travel the mountains that much I didn't look into what had changed. I am getting ready to go to the mountains again so I wanted to see if any one else had this experence. I always travel the same road and pull the same car.

rednlh · 06-05-2007, 05:59 AM

I have a 2002 Dolphin on a workhorse chassis with a 8.1 gas engine and a 1000 allison translmission. When I first started going to the mountains, I was not using the breaks a lot to slow down when I went downhill. I was told to have the engine and transmission reflashed by workhorse due to transmission downshifting. On the next trip to the mountions, I had to use the breaks a lot and they were getting very hot. It seams like the engine wasn't slowing me down. Since I don't travel the mountains that much I didn't look into what had changed. I am getting ready to go to the mountains again so I wanted to see if any one else had this experence. I always travel the same road and pull the same car.

rvten · 06-05-2007, 06:58 AM

Welcome to the forum.

OK are you down shifting before going down the hills and mountains? Usually same gear going down as you used going up.( you may need a lower gear if grade is steeper on down side) I usually turn off or lock out 5th gear with dash switch.

DriVer · 06-05-2007, 07:03 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rednlh: </div></BLOCKQUOTE>Hello and welcome to iRV2.com.

Regarding compression braking with the Allison 100LCT transmission - it's quite easy!

When you are approaching any downgrade where you think you are going to need to control your forward speed, go ahead and turn the OD switch to OFF. This will downshift you to 4th gear.

That accomplished reach for the column shifter and depending on the down grade either choose 2nd gear or 3rd gear. (Before you start going too fast) 2nd gear will hold you back much more so than 3rd. Don't fear about blowing anything up because the Allison can handle the job.

Watch the Tach and if it gets up to 4,000 RPM line tap your brakes in approximately 1/2 second applications. Continue to do the brake application until the vehicle slows down. This process will slow you down quite a bit without over heating your brakes.

Once you find yourself decelerating slower than the posted speed limit (within reason) you can then upshift to the next highest gear. This will speed things up and once you've flattened out the hill shift up to 4th.

You can then turn the OD back on.

This is a technique that you will learn fairly quickly. The thing is not to over rev the engine and don't be afraid to manually down shift to 1st if you have to. If you are in first gear just make sure there is an insane grade that you are trying to descend and then watch your RPM like a hawk. Use the brakes only to control RPM until you've slowed up enough and then begin shifting up one gear at a time.

Full-Timers · 06-06-2007, 04:47 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rvten:
Usually same gear going down as you used going up. </div></BLOCKQUOTE>This statement does not hold true anymore since engines produce more torque and HP than they did in the past. You can climb a hill in a higher gear than in the old days when this statement was true.

max49 · 06-06-2007, 05:08 PM

[QUOTE]Originally posted by DriVer:

Watch the Tach and if it gets up to 4,000 RPM line tap your brakes in approximately 1/2 second applications. Continue to do the brake application until the vehicle slows down. This process will slow you down quite a bit without over heating your brakes. end QUOTE]

Driver, That's exactly how I go down hills but I've had mine at 46, 48 and even 5000 RPM both under power and coasting down hill. Is it gonna blow up on me?
I could use another gear. Sometimes it'll hit the rev limiter, 5000 RPM, in 1st gear but it can't pull 2nd gear. Or at least, it seems like it would be harder on the engine and tranny if I tried to force it.

DriVer · 06-06-2007, 05:26 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by max49:
I could use another gear. </div></BLOCKQUOTE>Max, Yes you could!

Your PCM will protect both the tranny and engine so I douibt you could blow the thing up.