1999 C/K3500 Duramax Conversion - Motor Mounts

[poyntern]

Folks, I've spent a great deal of time reading the conversion posts, surfing the internet and buying diesel magazines (including the Duramax Conversion Guide) trying to find a source to PURCHASE the engine mounts for this conversion. Yet all to no avail, at least so far. Hence I thought I would try a post to see if anyone knew of someone who was building and selling the mounts. I would be quite happy to purchase rather than manufacture them from a efficiency perspective. That's my initial question on this path I've chosen to take. I must say that I am very happy to see so many others who have been here before from which I can learn and gather knowledge. I have completed cummins conversions into Chevy's in the past (1991 3500 single wheel crew cab (87 Body Style), 1970 GMC 5500 Cummins/Allison) those however were not as daunting from a wiring perspective as the Duramax is.
Thanks in advance for your guidance on this subject.

[More Power]

If there's interest beyond just a couple sets, I'd look into having a local fab shop produce the mounts for us (and you). Let me know.

Jim

[THEFERMANATOR]

From what i learned from doing mine, I would reccomend building your own to match your set-up. Slight changes in how the mounts are welded together can make the difference between hitting the hood or your steering. People with 2WD trucks can lower the engine down some and get more hood clearance whereas the 4WD app needs to be a bit on the high side.

[87max]

For my application I used stock duramax motor mounts & modified the receiving mount that bolts to the frame (intermediate mount). I then welded in a piece of angle so that it sat on the lower flange inside the framerail bolted through the side & bottom of the frame into that angle modified mount. Then to err on caution I made a crossmember that wrapped up the outside of the frame to tie it all together with the bolts passing through all three.

[poyntern]

Thanks for the replies thus far. Jim any thoughts on cost? I'd be willing to sponsor more than one set if they are reasonable. I have to assume there are folks out there trying to do this. Destroked, and FordCummins seem to be doing a good job of producing parts and pieces for the cummins conversions into Fords. I would think if a person could bundle together a bit of a package, as they have, for the Dmax conversion there would be interest.
I do see the benefit of fabricating my own, but I travel extensively and need all of the 3rd party labour I can get reasonably to make this conversion happen.

[More Power]

I'll visit the fab shop this week, and see what they can do for us. I'll post back to this thread by Friday.

Jim

[poyntern]

Thanks Jim appreciate that. I'm in Calgary I believe you are in Montana?
Actually right now I'm in the Gold Coast of Australia which is having much better weather than Calgary

I have reached out to PPE as well regarding a standalone harness? I have read a few posts on the subject and this seems to be a very viable way to go. I have not seen posts on using a cable driven throttle assembly. Is it even possible or does it need to be fly by wire?

Thanks!

[DmaxMaverick]

The throttle would need to be fly-by-wire at some point. There's no place/device to connect a mechanical throttle input on any GM Diesel since 1993. The Duramax fuel system is 100% PCM controlled, and earlier models are driven by a separate EDU/FICM. There's no rule that says the APP has to be on the firewall, and you could place it at the end of a throttle pedal cable. However, that would be one more moving part to cause grief at some point. The APP systems have proved to be extremely reliable over the years, with only slight mechanical changes and no functional design changes since inception.

[poyntern]

Thanks that is great information. Appreciate the detail. I did not get a pedal with the engine I purchased, I know I know doing this piece meal is a problem. Thus, I need to source the assembly etc. I was contemplating going mechanical if it was possible. So short of a few keystrokes I've not expended any unnecessary energy!

[poyntern]

Hey Jim,
Any luck with the fabrication shop?
Thanks

[poyntern]

Everyone,
I will post pictures in the next few weeks of the mounts I had water jet cut and welded up for my conversion. The guide and patterns included in it were very very helpful and a big thanks to Jim!!! I've made some modifications (as is always the case). The engine is in and running based on a standalone harness crafted by the shop I have the truck at.

Next step is to mount the intercooler with the least amount of cutting possible (LOL).

Now for the controversial part of this post. I've left the 4L80e in place

So we'll see how that holds up and for how long LOL.

I'm basically treating this as a van configuration and through EFI live tuning tweeking to try and save the transmission.

Some points worth mentioning as I've not seen them elsewhere (could be wrong so please excuse me if these are duplicates)
Fuel Sending Unit - 2002 LB7 will mount in the 1999 OBS truck tank and the fuel gauge appears to be accurate (still testing) with only minor modification. Trim an alignment tab and swap the o-ring.

Duramax Van has a different flex plate GM Part Number is 12621644

More to come thanks to everyone for their help and comments thus far.

Norm

[More Power]

Good job on the sending unit! You did something I wanted to do, but couldn't force myself to spring for the OE cost on a hunch it might work in a GMT400 fuel tank. Although I have suggested to others engaged in a conversion, and who had a complete salvage truck as parts, that it should be possible.

I haven't had the time yet to get the mounts made, but I will....

What's different about the flexplate? Back during the trial fit days, when no one knew whether a conversion possible, I bolted a TH400 3-speed auto to the Duramax, and then bolted it all into the truck. The flexplate worked fine for the TH400, which uses the same torque converter bolt pattern as the 4L80-E (the 4L80-E is an OD version of the TH400, or so I'm told).

Jim

[westerncorvette]

Where the torque converter bolts to the flexplate it is raised so that the torque converter doesnt have to pull together quite as far.

Both the fuel sending units have the same resistance reading and pivoting point so it will read exactly as it did before.

(What am I doing researching on my day off!)

Les

[poyntern]

The flexplate where it bolts to the TC reminds me of the "normal" chevy automatic flex plate with the raised mounting points. It was also balanced differently than the Allison flexplate as I recall.
I don't think we took any pictures before it was installed I'll try to get some pics of it with the inspection cover off.

The next biggest challenge to be tackled is the intercooler. I've seen many approaches (thefermanator, GordonMarks etc)

Anyway, pictures and bit more of a detailed write up to follow.

[poyntern]

And of course the Dodge IC in the conversion guide!!!!

[More Power]

The flexplates used in the 6.5 diesel or a gas engine are balanced for the engine. No balancing is required for the transmission. The bolt circle and setback are important though - i.e. there should be a little clearance between the flexplate and the bolt lugs on the torque converter - before the TC is bolted up.

There can be many intercooler solutions... A Dodge or Duramax IC would work with modifications, as would a strictly custom version. Cost is why I went with the Dodge IC - they were available on eBay for reasonable prices, but I couldn't locate a good used Duramax intercooler at the time. And.... I know of one conversion in a 1998 K3500 dually running without an intercooler at all.... though I'd have to have one in a truck used to tow.

Jim

[THEFERMANATOR]

Not trying to be a buzzkill, but be careful on teh power through the 4L80E if this is in a truck. Also the achilles heel will be in teh TCM. I'm not aware of any TCM that will interface with the DMAX for a 4L80E trans other than the LBZ van's T42 which uses CAN bus. If your using a LB7 or LLY, I don't believe you will have shift energy management to defuel for the shifts which is where the DMAX's torque kills trannies. I know they are using them in cars, but that is 3K pounds VS 6K+.

[poyntern]

Agreed!
I just wanted to try the 4L80e and see how it goes. The engine is an LBZ and I bought it alone without a transmission or a T-case. So we'll see.
I suspect I'll need to set up the TCM as per the van configuration, but we'll see how it goes. Should be able to do a test drive this week as for now we just have the turbo and IC piping looped together till we land on an IC.

I have ordered an aftermarket rad support which will be here on Tuesday and I have a Dmax intercooler so I'm going to try this route to begin with. Basically following what Thefermanator did based on his pictures.
I have some pictures thanks to Gordon Marks as well with respect to modify the inlet horns on the IC and may follow that advice as well to avoid modifying the inner wheel wells.

I don't recall any comments on the impact to the Windshield washer bottle on any of the posts?
Any comments Jim or Thefermanator?

Here are a couple of pictures of the "LOOP". Thanks to Les at Western for this!

[THEFERMANATOR]

If you program the ECM for a VAN be aware that the wiring pinouts are different than that of a truck. You can wire it like a van and hook in a T42 TCM though and control it with all van programming. If you decide to go the van wiring and programming route, get ahold of member "pussow" over at DP as he had his truck set-up that way at first(he swapped over to an ALLISON though after a year as I believe he found teh 4L80E couldn't hold much over the 250HP stock van tuning). He is also the one that sells the conversion disc on Ebay.

[westerncorvette]

So we got our truck running good but one issue we encoutered was that we keep having to prime the system to get it to fire. It seems like its draining back into the tank. Once its running it runs fine.

Any thoughts? Should there be a checkvalve somewhere as there wasnt one in the 02 Duramax fuel sending unit we installed.

Thanks

Les