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Author Topic: 12v Cummins Swap/'73 GMC 2500  (Read 4941 times)

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Offline KensAuto

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12v Cummins Swap/'73 GMC 2500
« on: December 07, 2019, 07:25:49 PM »
This is the one vehicle that I'm attached to. My '73 that was purchased on payments in highschool, owned by my shop teacher. We painted it in the body shop, with free paint, school bus yellow... just before I acquired it.

About 14 years ago the original body, abused from 4 wheeling and mudding, was replaced by pieces of a '78, '82, '87, etc. and painted to match my 2000 half ton. The power plant is currently a 66 Pontiac 400, which replaced the worn out 71 Firebird 400, which replaced the blown (up) 350. She also has a 4sp backed up with a 205 transfer case.

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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #1 on: December 07, 2019, 07:35:59 PM »
I wanted to install a diesel when I rebuilt the truck, but didn't have the funds, nor the time. I had built the 2nd Pontiac engine to install in a Tempest so it was an easier solution at the time.
A Duramax was the original dream, just because I'm a GM guy, but just don't want the headache.

She lost the AC compressor a few years ago so I parked it. A couple weeks ago we pulled the fuel tanks out to clean, and shortly after, I came across a great deal on a '86 square body that was already swapped.
.. impeccable timing.

This is that truck. It's a western hauler conversion which probably had a big block. I bought it cheap not knowing if the engine was good, or what year it was. All I knew was that it was 2wd, NV4500, and had a P-pump.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #2 on: December 07, 2019, 07:43:39 PM »
It didn't take long to get it running, and it sounded great. Took it for a drive to check out the transmission and found the 3rd gear synchros toast.
I was so excited about this project that I pulled the engine/trans the next day.

The oil fill tube had unscrewed itself from the timing cover and made one heck of a mess over the years. Can't believe no one noticed. It took me over 4 hours to steam clean the engine, trans, and radiator.
« Last Edit: December 07, 2019, 08:12:04 PM by Nate »
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Offline oklawall

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #3 on: December 07, 2019, 07:54:23 PM »
This sounds like this will be fun to watch. By the way I'm a firm believer in that a a clean engine/transmission makes a happy mechanic

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #4 on: December 07, 2019, 08:03:43 PM »
Dang pics keep turning around.

The engine ID plate on the front cover says it's a '90, 160 horse motor, so I would assume a certain devious dowel pin probably took out the original housing, and no one saved the original plate. The P-pump numbers show that it's one of the more desirable engines, a '96, 215 horse, manual trans. I'm good with that.

...best part is that I got 2 additional engines with the truck. After running the pump numbers, they are both '95s, with 175hp.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #5 on: December 07, 2019, 08:17:01 PM »
First task is to relocate the AC compressor. The old Chevy's had fairly narrow frames up front. In the pics below you can see where they just chopped and folded over the passenger side frame to make room in the 86. I don't want to cut the frame.

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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #6 on: December 07, 2019, 08:26:01 PM »
A common option is to use pieces from a medium duty truck. They have high mount compressors, but I don't want to spend the time and money trying to source all the correct parts, which leads to a third option...
...aftermarket relocation brackets. These seem to range in the $600-1200 range.
Not unless I'm forced to. Trying to keep this cheap, being my slow season at the shop.
Here's where I'm at right now. I layed the alternator over on it's side. I modified (narrowed) the upper alternator mount (thermostat housing) to the same size as a Sanden style compressor, (minus 1/4") that I had in the shed.
Then made a 1/4" bracket going from the main Alt. bolt up to the main compressor bolt. I welded a side brace that bolts to the oil cooler.

 Side note: If this fails I guess you all will be witnesses. Lol

« Last Edit: December 07, 2019, 09:05:45 PM by Nate »
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #7 on: December 07, 2019, 08:31:59 PM »
Just so happened that the original upper bracket for the alternator fit the other set of lower ears on the compressor, by trimming the welded on nut by 1/8". Just need to drill them to 3/8" to match the compressor ears.

This is as it stands right now.

« Last Edit: December 07, 2019, 09:06:23 PM by Nate »
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #8 on: December 07, 2019, 08:39:19 PM »
How the body of the western hauler?
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #9 on: December 07, 2019, 09:32:31 PM »
Drivers side doors are pretty beat up. Rest not too bad. Thinking about using the bed on mine. I think dual swampers look pretty good.
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Offline wilsonphil

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #10 on: December 07, 2019, 09:57:41 PM »
Ken its out, if it were me I would pull the cover and check the timing case bolts and KDP AND pull the pan and see what one of the rod bearings look like.

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #11 on: December 07, 2019, 10:48:11 PM »
We're tracking the same. Already got gaskets, kdp fix, and beige paint. As soon as the AC is sorted, I'm going to reseal it.
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Offline wilsonphil

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #12 on: December 08, 2019, 12:36:39 PM »
dont forget about the gearcase bolts, id pull everyone you can get too and locktight them

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #13 on: December 08, 2019, 01:38:13 PM »
dont forget about the gearcase bolts, id pull everyone you can get too and locktight them
Will do boss.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #14 on: December 08, 2019, 01:42:16 PM »
So today I'm just trying to finish this bracket while also trying to keep warpage down. This cross piece should finish it off in the strength department.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #15 on: December 08, 2019, 01:48:30 PM »
Now for the tensioner. I thought it would be easier keeping it Dodge so I went through the catalog and found a compact unit for an early V-10. I need to space it out 7/8" from the new bracket.
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Offline JR

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #16 on: December 08, 2019, 09:29:23 PM »
Sweet so far, another fluid change!

 :likebutton:
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Offline TexasRedNeck

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #17 on: December 08, 2019, 10:10:35 PM »
Nah. This one will get done


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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #18 on: December 09, 2019, 11:40:12 AM »
Nah. This one will get done


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Ouch.

.. not if I keep making mistakes like putting the tensioner bolt in the middle of the belt routing. :Facepalm
Looking for a specific allen bolt now.
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Offline wilsonphil

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #19 on: December 09, 2019, 04:22:10 PM »
Don’t forget the motor is all metric

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #20 on: December 09, 2019, 10:43:59 PM »
Ended up using an allen bolt, with the head turned down on the lathe, to mount the tensioner. Also added a wider pulley to make proper contact with the 8 rib belt.
After lacing the belt on, in a completely different pattern than the original, I realized that the alternator didn't have enough contact on the pulley.
I added an idler pulley where the original tensioner once resided. Time will tell if it's enough.

The new belt is exactly 4 inches longer and not hard to find.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #21 on: December 09, 2019, 10:53:35 PM »
While I was working on the front I decided to install a top dead center pointer. I used the timing pin to locate TDC then cut a groove in the balancer. Then made a pointer that bolts to the cover and case. To those that aren't aware, the Cummins balancer can bolt on in 4 different positions, *90 apart. I'll have to keep it in the right location for the pointer to work.

I made the plate large enough to remount the crank position sensor if I ever desire to run a tach. (Took the sensor off when rerouting the belt)
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Offline JR

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #22 on: December 10, 2019, 12:00:49 AM »
Nice mod vs buying all those parts.
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Offline Flyin6

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #23 on: December 10, 2019, 09:23:45 AM »
The inventiveness of all youz is wonderful to see!

Keep learnin the rest of us PP
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #24 on: December 10, 2019, 08:40:57 PM »
Got tired of working on the engine today, especially since it was cold outside and there isn't room in my tiny shop for it, so I started on converting the NV4500 2wd trans to a 4wd.

First, I layed out the necessary tools and gasket kit...
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #25 on: December 10, 2019, 08:58:24 PM »
Just kidding of course^^^ (forgot the pipe wrench)

Then tore it down.
Disclaimer: There's basically 2 mechanical type jobs that I usually won't do for customers. Rebuild transmissions, or rear differentials. So this should be interesting.

I received a rebuilt kit that includes an updated 4wd main shaft and 5th gear, with a new locking nut to hold it on. This is the main failure point on the 4500...the nut comes loose causing a mess. The updated shaft has full length splines for 5th, where as the stock one is only splined 1/3 of the way through the gear.
« Last Edit: December 10, 2019, 09:00:23 PM by KensAuto »
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #26 on: December 10, 2019, 09:05:59 PM »
And that was it for today. Found some bad hard parts (didn't come in the kit) which would make it extremely difficult to shift into 3rd gear, which is funny because when I drove it around the yard before teardown it wouldn't shift into 3rd. Go figure.
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Online EL TATE

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #27 on: December 11, 2019, 12:48:41 PM »
Got tired of working on the engine today, especially since it was cold outside and there isn't room in my tiny shop for it, so I started on converting the NV4500 2wd trans to a 4wd.

First, I layed out the necessary tools and gasket kit...

cold like what, low 70's, lol?
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #28 on: December 11, 2019, 12:59:51 PM »
40s !!!
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Offline TexasRedNeck

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #29 on: December 11, 2019, 01:49:01 PM »
Wow. They probably shut down the town. It was 42 here this morning.


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Offline JR

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #30 on: December 11, 2019, 03:51:09 PM »
Colder here in Kali,,,,,,,,,,,
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Offline cruizng

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #31 on: December 11, 2019, 04:31:21 PM »
Well I'm sure Sam will chime in from Way up North but it was minus 14 this morning with a wind chill of minus 28. Again.. balmy for Sam.. :)
Mike
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Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #32 on: December 13, 2019, 07:05:48 AM »
While I was working on the front I decided to install a top dead center pointer. I used the timing pin to locate TDC then cut a groove in the balancer. Then made a pointer that bolts to the cover and case. To those that aren't aware, the Cummins balancer can bolt on in 4 different positions, *90 apart. I'll have to keep it in the right location for the pointer to work.

I made the plate large enough to remount the crank position sensor if I ever desire to run a tach. (Took the sensor off when rerouting the belt)

i ran an autometer diesel specific tach that reads off the alternator and can be tuned depending on pulley size. did it on the kaiser as well as turners rig.

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #33 on: December 13, 2019, 09:15:15 AM »
I was curious how his tach worked, just forgot to ask. Good info.

Finished the transmission yesterday. Had to make a socket for the 5th gear nut. Torque is supposed to be 275ft lbs...using a large prybar, I turned it 'til my shoulder clicked. Should be close.

Snagged a cast iron 4wd tailhousing off of eBay. Now I need to spend some coin on an expensive adapter to hook up the 205.
« Last Edit: December 13, 2019, 09:58:46 AM by KensAuto »
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Offline TexasRedNeck

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #34 on: December 13, 2019, 10:46:53 AM »
275?  Four foot cheater bar with your feet off the ground??


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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #35 on: December 13, 2019, 12:04:01 PM »
and a jack handle
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #36 on: December 13, 2019, 01:04:17 PM »
Tack weld the nut in place and forget it.....
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #37 on: December 13, 2019, 07:01:27 PM »
Thanks Shawn for being so helpful. I knew I could count on you buddy.

Started resealing the engine today. Took the pan off first to check out the bearings, only to make WilsonPhil happy, per his request. (It passed his critiquing).
Also looks like someone balanced this motor. I'll probably pull the head to see if anything else was modded.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #38 on: December 13, 2019, 07:07:54 PM »
Also received the new blurple mount brackets. The old ones were made to fit some old Ford 390 pancake style mounts...not very strong at all.
The new ones fit regular gm mounts.
My employee had some poly ones that he donated to the cause.

First pics are the Ford ones.
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #39 on: December 13, 2019, 07:37:33 PM »
Thanks Shawn for being so helpful. I knew I could count on you buddy.

Started resealing the engine today. Took the pan off first to check out the bearings, only to make WilsonPhil happy, per his request. (It passed his critiquing).
Also looks like someone balanced this motor. I'll probably pull the head to see if anything else was modded.

Well, you know us welding types.....
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Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #40 on: December 15, 2019, 09:01:16 PM »
what kind of 205 do you have?

Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #41 on: December 15, 2019, 09:03:22 PM »
.. i have the 205 you need. but it would maybe be more expensive’r than what you can get from precision. hahah

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #42 on: December 15, 2019, 09:03:52 PM »
From 1973, pass drop, 10 spline. Figure 8... guess I have to mil the case for the larger 29 spline female.

What do you have?
« Last Edit: December 15, 2019, 09:06:14 PM by KensAuto »
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Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #43 on: December 15, 2019, 09:06:12 PM »
From 1973, pass drop, 10 spline.

you’re going to have to big bore swap the 10 spline over to 29, yes?

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #44 on: December 15, 2019, 09:06:45 PM »
i have a getrag 29 spline 205 from a first gen  :rolleyes:

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #45 on: December 15, 2019, 09:18:42 PM »
29 spline 205 with adapter



and this was a 27 spline 80mm small bore case.

now, it’s going to be a 31 spline 90 mm big bore case for a 203/205 doubler.


Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #46 on: December 15, 2019, 09:37:41 PM »
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Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #47 on: December 15, 2019, 09:40:58 PM »


and you’ll need a 29 spline male.. then a 29 spline female/female (if you go the route i’m thinking you are. if you have a way to do it with a 29 spline female input for the 205.. please disregard previous statement lol)

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #48 on: December 15, 2019, 10:29:46 PM »
The kit I'm looking at is 29 female that hooks up to the new 29 output on the nv4500. Over 5 bills.
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #49 on: December 15, 2019, 10:59:48 PM »
Can’t you source a 32 spline output from another nv4500 and use a ford np205 32 spline input?

I might know someone who has both btw......  :tongue:
« Last Edit: December 15, 2019, 11:01:24 PM by stlaser »
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