502 Ramjet and 4L80E

Mudbone · Newbie Joined: Jan 02, 2006 Posts: 1

I am in the planning stages of building up an off road 88 Suburban 3/4 ton 4x4. I would like to use a GM 502 Ramjet with a 4L80E tranny and a 205np transfer case. While I have not fully researched the 502's ECM, it seems that there are two versions, a MEFI3 and MEFI4. Apparently the 4 is the new version but there are plenty of 3s still avalible.

Would your TCU need to communicate with the Ramjet's ECM and how is that connection made? If not, what type of information would your unit need from other sensors? Do you have a wiring harness for this combined application? As far as the tranny and your TCU is concerned, is there a preference between the MEFI3 and the MEFI4 units? I am very curious as to how these two computer systems are going to work with one another and how I would go about programming them properly.

Also, is it correct that your TCU will allow me to switch between normal automatic mode, and full manual mode? Does your unit have a feature for manual lockup of the torque converter? If not, can a manual lockup torque converter be used with your TCU?

jballenger · Posted: Tue Jan 03, 2006 3:14 pm Post subject:

Our TCU does not need to specifically communicate with the MEFI3 or MEFI4. The TCU can share sensors with the MEFI. The only required inputs for our TCU are load (preferably a throttle position sensor), power, ground and connections to the transmission itself. Most installers will also connect rpm, map, coolant, brake light and any custom functions desired by the customer. We do make a harness specifically for 4L60E/4L80E applications and the wiring in your application should be very straightforward. The TCU wiring diagrams are here: http://www.powertraincontrolsolutions.com/downloads-cat5.html .

The MEFI4b (there is a 4a and 4b version) does use a J1939 CAN bus system which could potentially send information to our TCU instead of double wiring the sensors but we have not specifically tested this configuration and I would simply recommend sharing sensors like TPS, MAP and CLT.

The TCU does allow you to switch between normal automatic mode and full manual mode. You can setup our controller to manually turn on or off the torque converter but there are several limitations to this concept. Mechanically, most torque converters are not intended to be locked in 1st and 2nd gears in the 4L80E. Manually locking the converter runs some potential risks. If you are doing rock crawling or something similar, I would suggest using two calibrations. The first calibration could be for normal driving conditions and the second one could be for off-road use or rock crawling (with early tcc lockup). You could switch between these two calibrations/modes with a simple button. You can use either of these calibrations/modes with automatic mode or manual mode shifting.

If you have any more questions, feel free to call, email or post here.
_________________
James Ballenger
Forum Administrator