Aggravating cruise control

[Max Hubrich]

I have an '02, 8.1 Vortec, and the cruise works fine- It will downshift every second , all the way to 4300 RPM's, to nail the set speed- .

I have recently driven over 2000 miles along the East coast, Maine to Eastern NC, then NC to Jacksonville FL and on to Gulfport MS- on I-10. This certainly is not mountainous terrain.
I have given up trying to use the Cruise control with any peace of mind and to avoid downshifts, to no avail. It seems I'm disengaging, re-engaging, feathering the throttle, building up a "head of steam" prior to climbing a small overpass, etc. It's just too much trouble and time consuming work.

I'm looking for a mod, or a new cruise control unit that will allow a decrease in speed, preferably hold a throttle position, or some such parameter, rather than "nailing" a pre-set speed.

I have heard some DP's have a "soft" cruise setting that allows some degradation of speed while climbing hills, overpasses, etc.

Any ideas ?

[JonBrazel]

This is likely your problem...

http://brazelsrv.com/PDF_Files/Allis...h_01-02_WH.pdf


You can send us your TCM and we will update it and make shift point changes if you would like....PM or e-mail for more info...

[max49]

Max, I see that bulletin is for the '02 with the Allison. Maybe that will help yours. My P-32 with the GM transmission is just like yours on cruise control. It, also is on a mission to not lose 1 MPH even if that means 5000 RPM. CC and the Rockies are definitly not compatible

[dieselclacker]

Max H,
You have described the way my late 2003 W-22 cruise control operates exactly. I seldom use it except on near flat terrain. I like you find it a PITA to keep on top of things when it is engaged on all but a flat road. Seems like allowing the 8.1 to lug down a bit and lose a bit of speed would be the way it should work, but alas as Max 49 has said above, mine too is on a mission not to lose over 1 MPH. even if doing so requires the trans to shift to third and wind the engine to 5000 or so RPM. If the reprogram of the TCM as mentioned by Jon Brazel above only brings yours up to snuff with the 2003 or later models, I would be hesitant to have it done.

Dieselclacker

Dieselclacker

[DriVer]

Quote:

Originally Posted by dieselclacker If the reprogram of the TCM as mentioned by Jon Brazel above only brings yours up to snuff with the 2003 or later models, I would be hesitant to have it done.

D, I've driven a rig with a 5-3 shift schedule and it's not fun. Reprogramming the TCM to accommodate the later shift pattern of the 2003 to 2005 TCM is something that I would indeed want to pursue.

If the ECM needs to be re-flashed after the TCM is done that can be arranged as well since the UP can be reinstalled for FREE.

MaxH, (just thinking) If you got the UP Grade Brake kit that would have the new TCM (5-3 fixed) plus the UP can be upgraded to complete the install. An ECM ProScan should also be run before the new UP is installed.

[dieselclacker]

I believe my 2004 Workhorse has the later TCM programming, and it will still shift all the way down to third to try and hold the set speed. Not from fifth directly to third, but will go very quickly through fourth and into third, depending on steepness of grade.

Dieselclacker

[mfire1339]

I too have an 2004 and the trans programing is as posted. Really stinks, and is "too slow to respond to throttle position". IMHO just bad programing. It's trying to protect the trans at the expense of the engine.


Mike

[DriVer]

Quote:

Originally Posted by dieselclacker I believe my 2004 Workhorse has the later TCM programming, and it will still shift all the way down to third to try and hold the set speed. Not from fifth directly to third, but will go very quickly through fourth and into third, depending on steepness of grade.

Dieselclacker, Yep that's the way it's supposed to work. The shift pattern will stop briefly in 4th gear on its way to 3rd if it can. I have seen where if the load on the engine is immediate the 4th gear transition was imperceptible.

The 5-3 downshift anomaly occurs all the time for instance when you're trying to pass a vehicle even if you are out of cruise. From 2003 and beyond the issue was resolved. You can still get to 3rd or lower if you floor the throttle and go full military.

[DriVer]

Quote:

Originally Posted by mfire1339 I too have an 2004 and the trans programing is as posted. Really stinks, and is "too slow to respond to throttle position".

Mike, How quick of a transition are you expecting? The new schedule needed to be delayed somewhat from the 5-3 downshift anomaly they resolved because the shift would happen immediately and it felt and sounded like the engine wanted to come out of the doghouse.

Personally I have driven both and I like the current schedule.

I'm running an Allison Ultrapower Grade Brake TCM mod and the shifts up and down are great.

[mfire1339]

Actually I would like a "no down" shift control switch. I'd like to pick the gear I want to go up a grade.


Mike

[DriVer]

Quote:

Originally Posted by mfire1339 Actually I would like a "no down" shift control switch. I'd like to pick the gear I want to go up a grade.

Mike, You can do that all day long, just select shift.

I know one thing, select up-shifting isn't something that you are going to want to do long term. In 2008, our coach was struck by lightning and it fried the TCM shift schedule. In order for me to move at all, I had to manually shift from 2nd to 5th and we did this for 2 days. It's not anything that I am looking forward to repeating any time soon.

[oemtech]

I have an 04 with UP and I use cruise 99% of the time. No issues. I just use the foot feet to push it out of OD BEFORE a grade and get the rpm's up around 3 grand. Usually that is all I need to do unless the grade is really steep, long or I was late in getting out of OD. On avg I run 8.5 mpg pulling my CRV.

["007"]

I have the UP on my 03 and I use cruise all the time, it will shift down going upgrade to lower gear come up to speed than shift to higher gear than maintains the speed set originally.
Have never had drop out of cruise since I had it programed back in Tenn.
Sure work better than the Fords I had, would always drop out of cruise.

[JonBrazel]

Max,

If you have a SGII with X-Gauge it would be a good idea to program in long term fuel trims for bank 1 & 2 and go drive and see what kind of numbers you are getting under light throttle and under load. You may have something else going on, and this would help to figure out what may need to be replaced or adjusted.

Thanks