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Discussion Starter #1 (Edited)
NV4500 to G56 behind 12 valve - DONE!

I run a transport company, specializing in moving antique and specialty cars, trucks, and motorcyles. My main rig is a 1997 Ram 3500 with a 12 valve cummins and NV4500. It has only 519,000 miles on it, and I recently stripped fifth gear.

I've wanted an extra gear for awhile, and looked at my options.

The NV5600, which came in these trucks 99-02, and 03-04 would be the simplest. However like the NV4500, overdrive is on the back of the trans, causing a weak point. Plus, the 5600 is getting hard to find, and most trans shops won't touch them, citing many issues.

So I started looking at the G56 used from 2005 to now. It is a German design, and the reviews out there pretty much say its God's gift to the manual trans Cummins crowd.

There are two G56 versions, the 2005-08, and the 2009-current G56a. The difference is that the early model uses a .79 overdrive ratio and the current model uses a .74 overdrive ratio. There is also rumor that the mainshaft and some internal parts were made of better steel (cryo-treated?) in the newer models, although I have yet to positively confirm this.

So, after thinking about it and checking the numbers I've decided to use a 2009-now G56a.
 

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Discussion Starter #2
2wd G56a transmissions are pretty scarce, but I finally found one through one of my parts places. It came out of a wrecked 2011 Ram with only 17,000 miles on it.

It came in today on a pallet, it's all wrapped up still, so here is a list of the knowns and unknowns.

Known:

The G56 is physically longer and taller than a NV4500, so there will probably be some clearance issues. Net research says I'll have to cut crossmember and hammer floor.

The G56 will (probably) bolt to the NV4500 adapter. The G56 uses an integral bellhousing.

The G56 is fixed yoke vs. my current slip.

Unknowns:

I'm not sure yet if the stock clutch and flywheel will work.

Speedo pickup may or may not work. I found a writeup online detailing how to use rear axle sensor for a speedo sensor.
 

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Good call on the G56. I love mine. Sounds like you'll need driveshaft modification to adapt your slip yoke shaft to the G56 output shaft. My driveshaft shop was able to sort it all out for me.

Good luck. We'll be watching.
 

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Discussion Starter #5 (Edited)
Got trans unwrapped and started measuring everything up. I mocked up a nv4500 adapter plate and clutch.

Everthing bolts up with exception of the clutch disc. The NV4500 uses a 12x1.25 disc whereas the G56 uses a 13x1.375 disc. The G56 input shaft is larger and the spline engagement sits approximately .75 inch deeper into the bell.

This left me with a few options:

1. Since I have been unable to cross reference a stock application 12x1.375 disc I would be looking at a custom disc. Even then I'm not sure it would have enough spline engagement.

2. Upgrade to a 13 inch flywheel from a NV5600 equipped truck. That would require a starter spacer adapter. Then use a 5600 clutch.

3. Use all stock G56 clutch components with a dual mass flywheel. This would require no spacer, but the dual mass is not the way to go.

So after all that, I called Greg at Southbend (over several calls) and his opinion is that I should use an aftermarket single mass G56 13 inch flywheel with my stock nv4500 adapter and starter. Then use a nv5600 spec clutch kit. This gives me the best of both worlds and does not require a starter spacer. Plus it gives me the correct engagement and depth. Instead of trying to piece together the stock pieces, I just ordered the Southbend kit, knowing if I blew the clutch in the middle of nowhere I could replace it with a nv5600 unit. Plus the Southbend single 5600 kit is rated to tow over 20,000 lbs. regularly.


 

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Discussion Starter #6
As a note, I was curious if I totally cheaped out on all clutch stuff how low I could go.

Valair (cheapest) g56 single mass flywheel - $250ish

Autozone NV5600 clutch kit - $239

So, with tax and shipping I'd be around $550.

Southbend kit with flywheel was $950, so almost double........for four times the clutch.
 

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Discussion Starter #7
Being that I'm now waiting for my clutch the plan tomorrow is to test fit my 19.5 wheels and tinker with sensors to see what I need to do.
 

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Discussion Starter #8
Sometimes I love engineers. 2 and 4 wheel drive G56 units appear to be the same. 2wd units just get this big flange.



And sometimes I want to take a rolled up newspaper to engineers. There is only one sensor on the trans. I wanted to see if it was a reverse sensor or vss. It (and most of the bolts on the trans) are inverted torx metric. Bad engineer.....swat swat.....go to your corner and think about what you did.



It's a reverse switch by the way.
 

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Discussion Starter #9
NV4500 (left) vs. G56 design. You can see the spacer bump that is part of the 56 setup. This is what makes up for the difference. As you can see, the starter gear is at the back of the flywheel to make the difference. The only other way this could have been achieved would have been to use an aftermarket 13 inch nv4500 flywheel with a crank spacer, but then I'm not sure what kind of starter issues I'd have, and whether or not the starter would engage.

 

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Discussion Starter #10
As a reference point, I measured with a straight edge from the bottom of the frame to the middle of the output, which came out to 6 1/2 inches. Being this is a center bearing truck I'll need to stay close to that.

 

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Discussion Starter #11
Stock shifter and boot. I'm hoping to use the 2011 boot, because this one looks like Dom DeLouise would use it as a hat. Shifter is in neutral position, and you can see the way it bends up towards dash. The six speed shifter is different, more of a straight rod to the driver, so I'm hoping to be able to use it to give more dash to shifter clearance so I can mount my CB there. Currently it would hit, so CB is under seat, making it a pain to use. We'll see!

 

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Discussion Starter #12
For anyone pulling a stock 97 shifter boot, here is something interesting - I unscrewed the boot but it wouldn't pop up. I even tried prying it. It took me a bit, but I figured out they use a boot inside a boot, with the inside one screwed to the floor and the outside one screwed to the inside one. Mine were quite stuck together and appeared to be one piece.

 

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interesting that the output housing seems to be the same between 4x4 and 4x2 transmissions...whats the output spline count and size on a g-56?

now you have me thinking...i came across another round bolt pattern 205 for cheap...if i could bolt that to a g-56 with the right input shaft on the 205 without modifying factory hard components....bounce

we'd all appreciate keeping us up to date with part numbers and such...lots of pics would be sweet. cheers :beer:
 

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Discussion Starter #14
As you can see in the one pic, the six bolt holes exist for a transfer case in the 2wd unit. As for spline count, I haven't removed the flange. I might when I get it in, so I'll get back with you on that if I do.

Trans measurments:

Bell to six bolt area (where a t-case would go) 29 inches

The face of the flange sticks one inch out, making 2wd bell to flange length 30 inches.

NV4500 adapter thickness 2 3/8 (ish)

So, entire length of my setup is 32 3/8 inches.

Stock total trans length for my 1997 2wd NV4500 without adapter is 32 1/2 inches from bell to end of slip yoke output.
 

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Discussion Starter #15 (Edited)
I needed a big trans jack (for use under a hoist) but couldn't find one in time, so I bolted my floor one to the top of my 1940's pneumatic air bumper lift. Quite redneck, but worked very well.



 

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Discussion Starter #16
And the NV4500 next to the G56. Quite a size difference. The shifter comes out in the exact same spot to the inch. Reverse light hookups are different. The bellhousing on the G56 is much larger and deeper.

 

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Discussion Starter #17
Southbend NV5600 vs. Stock clutch.





New flywheel came with longer bolts, which were necessary.



And new flywheel and clutch installed. Everything was super heavy.

 

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Discussion Starter #18
Trans went in easily by jacking up front of motor. Contrary to what I read online, floor modification was not necessary.

 

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Discussion Starter #19
I pulled the flange to see if it indeed is the same as a 4x4 version. It is. The output spline is 29. I also took a spare 4x4 case just to "be sure" and it bolted right in with plenty of spline engagement. So yes, 2wd and 4wd G56 transmissions are the same. And, 2wd and 4wd dodge crossmembers are interchangeable.



Bolting up



And in, but its not staying. Nice to know a 4x4 conversion wouldn't require a trans change.

 

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I Love your trans jack arrangement!!!!! That is hilarious!!! LMAO!!!
 
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