Jump to content
03' Big Red

Allison conversion

Recommended Posts

I want to swap in a Allison 750DRD in my 2003 RD688S

i run the Eaton 8LL now... no computer on trans

my question is how will my ECM be effected ?

amd what year donor chassis would work to get all the pieces needed?

i am looking at a MR for the donor chassis 

Edited by 03' Big Red

Share this post


Link to post
Share on other sites

I talked to my local Mack dealer, they contacted Mack engineering who wouldn’t release any info.

i did find several 2001 LE donor chassis with the 4500 series trans, would the mounts and such from the LE work in my RD ?

i would appreciate any information in regard to what I may have to change in my ECM, and if any changes are needed can a competent shop make those changes? Or would I have to find a dealership that would make things happen?

Share this post


Link to post
Share on other sites

Pretty big undertaking.  Special transmission wire harness, and engine wire harnesses needed. Does the donor chassis have the same engine type as your RD, then maybe you could just pull the donor ECM. Not sure about component shop flashing new software.  Flywheel housing should be the same, but flywheel needs swapped out and you need the spacer ring. Allisons are very heavy and require rear buggy spring mounts at the rear of the transmission, so you probably need to fabricate brackets on your frame.  I'm not familiar with where the RD rear engine mounts are located (Flywheel Housing or Side of transmission) in either case they will not likely be the same.  There would probably be more headaches along the way, that I'm not thinking of.

Hate to say this, but I'd recommend trading your truck to get the transmission you want.

Pic of buggy spring

image.png.29f10247c96cf40427ef963455429239.png

  • Like 1

Share this post


Link to post
Share on other sites

Thanks for the info, I did find a RD single axle that would work much better.

Share this post


Link to post
Share on other sites

I would really like to keep this truck since I know what I have and to find a RD with a automatic set up like I need is fairly difficult.

i did find a 2003 RD on the internet with a Allison VIN # 1M2P296C23M066900  

this should help me create a parts list if I can’t find a suitable donor truck, my guess sticking with a RD would be my best bet for a donor truck.

 

Share this post


Link to post
Share on other sites

Ok folks 

i am still  working on the details of this swap, I have a vin From a 2000 rd with a Allison, can anyone tell me which Allison this unit has and 1st gear ratio and also the axle ratio ?

Vin 054124

also talked to another Mack tech and he says all that’s needed for the engine computer is to change the top gear ratio and change it to A designation for the automatic..

i would appreciate any other input in this swap, I plan to use to 750DRD for simplicity 

I also need to know what bell housing,flexplate and mounts to use.

 

 

Share this post


Link to post
Share on other sites

I have looked into doing an Allison for a 1985 MH with an E9-V8. The big issue is to get the trans to bolt up to the engine. The bellhousing that you have should work as it is a SAE #1 or something of that sort. From what I know most trans have the same housing diameter and flange, but I am no expert. There is a 13/16 inch spacer available to set back the trans. As for flex-plates there are several different ways to get the starter gear and torque converter to bolt up, maybe gear on torque converter. I have no choice but to make a custom steel "flexplate/flywheel" as the E9 is counterbalanced in the flywheel. Still working on that. The rear of the trans does need supported like in the previous illustration and not solid mounted. Trans I am going with is a HT754CR, 5 speed without deep reduction. What is going to make this all work is a cable shifted trans, no electronics. My truck does not have any electronics and the early Allison's were cable shifted before they had the brain. Actual RPM shift points are set in the valve body with spring pressures, that is old school as well and having someone do that setting is hard to find these days. As for help from Mack there really is no one there that could tell you much about older "Mack" trucks as they are focused on new Volvo stuff, just plain forgot or retired. Retrofitting is going to be all on the guy (you) that wants it bad enough to figure it out to make it work. Torque capacity for that HT750 is 1450 ft/lbs but can do that load all day long, is that matched to your engine torque rating? I am just playing with this E9 and will never be fully loaded.

Share this post


Link to post
Share on other sites

I don't think mack fitted any Allison to their E9, but I have somewhere a book with all the adapter p/n from Allison to fit on mack engines. You will probably be done before I put my hand on it again.. You might have better luck asking the guy who did the Bandag Titan in Australia (I believe) they made it for sure and might have spare parts 

Share this post


Link to post
Share on other sites

Is that HT754CR going to hold up to a E9 ? I thought the torque rating was much lower than the 750DRD 

Am I correct the 1st gear ratio is 8.0 ? Or something like that on the 754

my truck has the AMI 370 and I would be pushing the torque limits. It’s around 1480 ftlb 

Edited by 03' Big Red
Bad spelling

Share this post


Link to post
Share on other sites
50 minutes ago, fullfuel01 said:

I don't think mack fitted any Allison to their E9, but I have somewhere a book with all the adapter p/n from Allison to fit on mack engines. You will probably be done before I put my hand on it again.. You might have better luck asking the guy who did the Bandag Titan in Australia (I believe) they made it for sure and might have spare parts 

Well you are close to being 100% correct. Mack did do 5 Superliner tractors with E9's for the military to move aircraft. Wish I could find one now... The same Mack engineer that did the 5 military E9 Allison's did the Australian Bandag drag truck, he did the 2500hp engine in that truck as well.  Super nice guy but as I said has forgotten most of what was done so long ago. I can say that all the parts were custom made by or for Mack but the blue prints have been long gone. He did give me a few pointers and wished me good luck, saying it can be done.

It would be great if I could get any of that Allison info from you!!

 

Share this post


Link to post
Share on other sites
Just now, 03' Big Red said:

Is that HT754CR going to hold up to a E9 ? I thought the torque rating was much lower than the 750DRD 

Am I correct the 1st gear ratio is 8.0 ? Or something like that on the 754

my truck has the AMI 370 and I would be pushing the torque limits. It’s around 1480 ftlb 

The MH is just a play truck now, not a money maker. The HT754CR has around a 3.8 first gear not a 7.2 or so as in the deep reduction as you are talking about. Torque capacity is basically the same at 1450 ft/lbs for all the HT700 series.

That Bandag drag truck had a 2500hp E9 with a HT700 trans and it did OK with no load and just drag racing. The MH should be OK for just bobtailing and an occasional trailer on it. If not the 18 speed will go back in.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...