The compushift is fully progamable. You can make it shift however you want from what I am told. I have not run one yet but want one. Also From what I was told by a dealer that sell it , it doesn't need an tach signal . It uses the VSS' on the tranny somehow.
Lets see, first you state that the "real only way" to make the 4L80E work "good" is a $1200 Compushift computer. When I pointed out this is incorrect, you come back saying the GM TCM "doesn't work nearly as good as a Compushift" and then express some third party information that you are really not clear on. I'm still waiting to hear, how is the Compushift appreciably better for a DB2 conversion? By you statements, you infer that the GM TCM doesn't work very well, at least not "good" enough, so what's the problem with it?
Just FYI, the GM TCM is programmable as well.
I actually have run one for years and they work good enough for me. I have corresponded with lots of others that have used one and they say they work "good". Jet sells them (at inflated prices) and they seem to have a good reputation. Jim over at the page did a project truck using one and he reported it worked "good".
So if you can't, maybe I can come up with some reasons why the GM TCM "doesn't work nearly as good as a Compushift" if converting from a DS4 to a DB2.
The GM TCM is a factory designed and manufactured item with thousands in use and almost no reported problems. If you needed a replacement, they are available through any GM dealer and many parts houses and salvage yards. The Compushift is an aftermarket item, and available at limited speed shops and mail order houses.
The Compushift requires a complete new wiring harness to be installed, along with a proprietary throttle position sensor, available only from Compushift. The GM TCM uses a factory GM TPS that bolts right up to the DB2 and is available through any GM dealer. It requires only a small amount of rewiring and uses your existing factory wiring harness to the transmission.
The Compushift can function with or without a tach signal. The GM TCM uses an easy to install factory engine speed sensor for its programming. I don't know if that makes it better, GM probably knows a little about how their transmissions work and in every application I'm aware of they use engine speed to program the transmission. They also use barometric pressure and know if the air conditioning clutch is on or off, just like the PCM you now have.
I'm not saying the Compushift is a bad piece, it very well may be a great trans computer. In some applications, it may have certain advantages. But for the application in this post (DS4 to DB2), I do not see how its any better than the GM TCM. In fact, the standalone GM TCM uses the same inputs and basically the same programming to operate the 4L80E as the PCM in the DS4 trucks. So, one could presume based on your logic, every DS4 equipped truck with an automatic doesn't work "good" and the only way to get them to work "good" would be the installation of a Compushift.
There may be people reading this that are considering a DB2 conversion and I would like them to at least have accurate data so they can make an informed decision. It would probably be of more service to your fellow Diesel truck owners if you stick to what you know and stop disseminating erroneous information as fact. Telling them they must spend $1200 for a trans computer when there are very good (and quite possibly superior) alternatives for a fraction of that amount is not really helping anyone. :nono:
