Converting early gas MH to Duramax? Possible?

[BigRabbitMan]

The question of the day is whether I should go with a 5 speed or a 6 speed. With my present rear end and wheels, which I will not change, the 5 speed would put the Duramax LBZ at about 2200 rpm at 65mph. The 6 speed would put the engine at about 1900 rpm.

To all of you Duramax folks that run with loads in that range a lot of the time, where should I target my RPM? Reasons?

Have changed the title to reflect the current question.

[BigRabbitMan]

Based on the discussion in this thread http://www.thedieselpageforums.com/t...ad.php?t=34258, the decision has been made to use a 6 spd.

Now to find an Allison 2550 which is the model with the lower 1st and 2nd gear ratios.

[BigRabbitMan]

It is time to update this thread - the action begins!

Today I aquired a 2006 GMC Sierra 4x4 with an LBZ and 6 spd Allison (47,000 miles). So now the project goes into high gear utilizing the time and talents of two people: myself and a fellow FMC coach owner. The conversion will be done at his house as I have no room at my house. He is also very talented mechanically, electrically and with control systems.

I still have the LBZ in the garage, but we decided that it would be best to get a "roll over" donor vehicle so that we could utilize the maximum number of other systems instead of the minimum number of other systems. It is now our intention to integrate the compete GMC dash module into the FMC dash including physically. We will disable any unused functions, but will otherwise have a stock gauge/dash module in the FMC.

Right now the biggest unknown is the transmission issues I have discussed above.
1. Will a Duramax ECM function as well with a non-GM TCM as it does with a GM TCM?
... or,
2. Will a GM TCM work with changed gear ratios in the Transmission?

If you can give any help or direct me to a source of information on these two questions, I would greatly appreciate it.

Wish us luck as I pick up the donor vehicle in a day or so. The LBZ in the garage will be sold when we are sure we don't need anything from it as well as all excess parts of the roll over donor GMC Sierra 4x4.

Stay tuned,

[BigRabbitMan]

Right now the biggest unknown is the transmission issues I have discussed above.
1. Will a Duramax ECM function as well with a non-GM TCM as it does with a GM TCM?

If you can give any help or direct me to a source of information on these two questions, I would greatly appreciate it.

Question #2 was answered elsewhere and the answere was NO.

That leaves Question #1. The reason for this question is that I am considering going with an Allison 2550 due to my driveline parking brake requirement. I would like to have it with the wide grear ratio if I can get it flashed as a 6 spd by Allison. If that can be done, then the question above is very pertinate as it is pointless if the LBZ will only function properly with a GM TCM.

My thoughts are that the LBZ functions with a manual transmission, it should be fine, but I can't find out what inputs other than output shaft speed, if any, are needed by the ECM.

Thaniks,

Thanks,

[BigRabbitMan]

That leaves Question #1. The reason for this question is that I am considering going with an Allison 2550 due to my driveline parking brake requirement. I would like to have it with the wide grear ratio if I can get it flashed as a 6 spd by Allison. If that can be done, then the question above is very pertinate as it is pointless if the LBZ will only function properly with a GM TCM.

After many discussions and consideration of verious factors, the decision has been made to use the Allison from the donor vehicle and its control module. I will not have the wider ratios for the first couple of gears, but I can live with that.

I have confirmed with the Allison technical advisor of Allison West that the GM 1000 can be converted from 4 wheel drive to 2 wheel drive with provisions for the standard driveline brake which is a requirement in my case. He will be researching the part numbers to pass along. The transfer case will be removed and the correct tail housing and tail shaft will be installed. He may also have a buyer for my transfer case!

Pictures of the donor vehicle (2006 Sierra 2500) are here: http://travel.webshots.com/album/579528614eUJYCC

As we move throught this project pictures will be added to that album.

A vacuum pump from a 2002 Lb7 has been secured to provide the vacuum needed for the brakes. I am still in need of a second alternator with bracket and an idler so that I will have a dual alternator setup.

Repair manuals have been purchased and have arrived so that wiring needs can be studied and the best procedure for removeing the harnesses from the donor can be developed.

... to be continued ...

[BigRabbitMan]

An update is in order. Work on the donor GMC Sierra has continued. Since we are working outside, we are subject to weather on Saturdays as well as family matters. The combined effects greatly reduced our work days these last two months.

We have desmantled the front end while tagging anything that we will be hooking back up in motor after the transplant. we are almost ready to extract the LBZ and Allison from the donor. It will then have the output shaft and housing changed from a 4x4 set up to 2 wd with a driveline parking brake.

I have posted a number of pictures at the link in the above post. Go take a look. As we progress I will continue to add pictures.

[BigRabbitMan]

We are doing a "full swap" to the extent possible in this case. You could do a "minimal swap" which would not involve the dash cluster, etc. and with that swap you would retain the original guages/dash. We are doing it as the full swap so that the benefits of the full guage cluster and the Driver Infornation Center (DIC) would be retained. This includes cruise control. The exisiting systems on all non-computer controlled engines will not work as there is no linkage for the cruise control to attach to.

An example of the two levels of conversion are like what we are involved in right now when it comes to the engine fan. The donor fan will not work as it is a puller and not a pusher fan. It also has an ambient air (exiting the radiator) thermal viscous clutch to control fan speed which also will not work as the air is going the opposite direction and will never engage the fan.

The simple solution would be to just remove the clutch and bolt the fan, by using an adapter, to the idler and have the fan operate at engine rpm the same as our fans do on the 440, 8.2, 5.9 etc. The drawback to that simple solution is that the fan is always drawing full horsepower for the given rpm and, therefore, energy and fuel.

In an attempt to improve on that situation and have the fan only operate at the speed needed for conditions, we are currently looking for a fan clutch/controller combination that will electrically control the fan speed via a viscous coupling based on engine coolant temperature. When cruising on flat land in cold weather the fan could operate at significanlty less speed than what is needed on a hot summer day if we find the right combination. Given the amount of air that the fan will be capable of moving, the difference can be significant over a number of miles.

Stay in touch as we work our way through this project. Your questions/sugggestions are always welcome.