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Old 02-23-2014, 05:46 PM   #81
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Re: 6.7L Cummins conversion project

Time to take a little break from the computer stuff and get my hands dirty. Got a used NV271 really cheap so the idea is to rebuild this one and use the one in my van on another project. To mate this to an Allison requires a little custom work so even if I were to use my current T-case, I'd have to tear it down to do all these mods anyways. I really didn't want to wait until my van was apart to figure this all out, thus why I'm doing this one instead.

To start off, I built an attachment for my engine stand that I could bolt the t-case to and rotate it around for easier work.


cases popped apart:


Chain and output shaft out:


Pile of parts:


And finally the real meat of the NV271 to Allison mating. On the right is the new input shaft. 29 spline out of a Dodge NV271. On the left is the factory Ford unit. Some obvious differences between the two shafts but they're the same size where they need to be. The only major difference to remember for assembly is that the end of the output shaft rides in a bearing on the inside of this shaft. On the Dodge, that bearing is set at a different depth than the Ford piece so I have to press that bearing into the right position before assembly. If I did nothing, the shaft would only be about half way into the bearing.




The other custom work necessary is to fit the output shaft speed sensor into the t-case output shaft housing and make an adapter ring because the mounting holes (t-case to trans) are way off.

When you convert the Allison tailshaft housing to the 4x4 unit, you lose the sensor provision so I need to do two things to the t-case... 1) machine a tone ring that will fit the output shaft of the t-case and have the right tooth count. This would be super easy if it weren't for the shape of the output shaft. I have a plan for what to do but of course it will require custom machined parts which = $. 2) The housing needs to be machined to accept the sensor. It is pretty important to get the sensor positioned precisely too so that won't be as simple as just drilling a hole.

fun stuff!!
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Old 02-23-2014, 07:45 PM   #82
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Re: 6.7L Cummins conversion project

We sometime mill the correct number of "teeth" in the output flange, making it the reluctor ring, and mount the sensor externally - just a thought. It is easier...

Quote:
Originally Posted by mgmetalworks
The other custom work necessary is to fit the output shaft speed sensor into the t-case output shaft housing and make an adapter ring because the mounting holes (t-case to trans) are way off.

When you convert the Allison tailshaft housing to the 4x4 unit, you lose the sensor provision so I need to do two things to the t-case... 1) machine a tone ring that will fit the output shaft of the t-case and have the right tooth count. This would be super easy if it weren't for the shape of the output shaft. I have a plan for what to do but of course it will require custom machined parts which = $. 2) The housing needs to be machined to accept the sensor. It is pretty important to get the sensor positioned precisely too so that won't be as simple as just drilling a hole.
.

fun stuff!!
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Old 02-23-2014, 09:16 PM   #83
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Re: 6.7L Cummins conversion project

That is one of the options I've considered. Do you have any pictures of this for a NV271/273?
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Old 02-24-2014, 12:07 AM   #84
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Re: 6.7L Cummins conversion project

Quote:
Originally Posted by mgmetalworks
That is one of the options I've considered. Do you have any pictures of this for a NV271/273?
Here is an example:

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Old 02-24-2014, 07:23 AM   #85
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Re: 6.7L Cummins conversion project

That is a case where you have some mounting holes conveniently located near the flange...
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Old 02-28-2014, 01:17 PM   #86
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Re: 6.7L Cummins conversion project

Quote:
Originally Posted by mgmetalworks
When you convert the Allison tailshaft housing to the 4x4 unit, you lose the sensor provision so I need to do two things to the t-case... 1) machine a tone ring that will fit the output shaft of the t-case and have the right tooth count. This would be super easy if it weren't for the shape of the output shaft. I have a plan for what to do but of course it will require custom machined parts which = $. 2) The housing needs to be machined to accept the sensor. It is pretty important to get the sensor positioned precisely too so that won't be as simple as just drilling a hole.
Now that you got me thinking about Allison's in the V10 thread.... Could the differential VSS be used instead? Obviously it has speed factor for the gear ratio, but a signal converter is cheap.

Your van doesn't have the diff tone ring anymore since it has RSC, but I imagine one will still fit mount up in there since it's still a Dana-60?
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Old 02-28-2014, 02:38 PM   #87
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Re: 6.7L Cummins conversion project

Quote:
Originally Posted by carringb

Now that you got me thinking about Allison's in the V10 thread.... Could the differential VSS be used instead? Obviously it has speed factor for the gear ratio, but a signal converter is cheap.

Your van doesn't have the diff tone ring anymore since it has RSC, but I imagine one will still fit mount up in there since it's still a Dana-60?
The Allison has its own speed sensors to feed info to the TCM and the TCM controls shifts based on comparisons of the data from the speed sensors. From the 4th gen controls manual:

"15. SPEED SENSORS
There are three speed sensors available for use with 1000 and 2000 Product Families transmissions: the input (engine) speed sensor, the turbine speed sensor, and the output speed sensor ... The speed sensors provide rpm information to the TCM. The speed ratios between the various sensors allow the TCM to determine the transmission operating range. Speed sensor information is also used to control the timing of clutch apply pressures, resulting in the best possible shift quality."

The output shaft speed sensor is for the trans, not necessarily for the rest of the van's modules. I can use the speed sensor data in other ways as it is available as output from the TCM. I actually plan on using that data for as much as I can get away with. I have a CAN ready microcontroller for message translating experiments but I haven't had time to program it yet.

As an alternative, you can put the output shaft speed sensor in the Allison 4x4 tailshaft housing. Destroked sells a kit for $599 to do it (you supply the $300 housing for them to machine). I am choosing to put the sensor in the transfer case because it is an $85 housing with, at most, a couple hundo in custom machined parts....and there's more room to work with.
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Old 03-08-2014, 03:47 PM   #88
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Re: 6.7L Cummins conversion project

The t-case I got was a pretty high mileage unit so my expectation was that I'd probably have to replace a few parts. The range fork happens to be the lucky part that gets to go into retirement this time around. In my search for a replacement, I wasn't having much luck finding the exact part so I opted to do the upgrade to the newer design. The upgrade requires a new gear along with the new fork and wear pads.

The updated design on the left



The wear pads on the old fork just plain wore out and then the metal to metal contact between the gear and fork ground away a little less than half of the mating surface.



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Old 03-16-2014, 02:56 PM   #89
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Re: 6.7L Cummins conversion project

Well...it's a pretty awesome day today!! I finally have all of the pieces of data needed to disable the security features within the engine ECM. WOO HOO!!!

A lot of items on the list were stacking up behind this one hurdle so to get past this is pretty awesome. Next big item is to run the engine on a stand before tearing down my van. I think that will be a valuable exercise and much easier to sort out the wiring in a wide open space. Momentum should pick up pretty fast from here. Maybe I still have a shot at a summer time transplant.
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Old 04-24-2014, 11:23 AM   #90
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Re: 6.7L Cummins conversion project

It's been a month, about time for an update huh?

My wallet has been on fire lately rounding up the remaining parts for this conversion. The major purchases are done, now I'm just down to the little things like fasteners, hoses and fittings.

I will be picking up a bare frame from a local wrecking yard within the next week or so. I had always planned on building an engine stand to sort out the wiring and plumbing before lifting the body off of my van and then one day it sort of hit me... Why not use a van frame for the engine stand and then you can build all of the motor mounts, trans cross member, frame-mounted battery boxes, fuel pump bracket, sort out the fuel line routing, etc... etc... etc... ??? I may end up cutting the frame down to make it easier to fit in the shop but that's the plan now. I really want as little downtime of my van as possible so getting everything dialed in before gutting my rig will be really helpful.

I know all of the electronics stuff is boring to you guys but I promise we're about to have some fun with the fabrication!
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