Engine/Transmission (1994 - 1998) Mission: G56 (pictures)

The mission is to install the big one where the small one used to be. My heartfelt thanks to Eric, aka ewcmr2 who paved the way.

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Besides the transmission, a new flywheel, clutch and PP are needed. My choice SBC single mass flywheel and ConO clutch kit. Also needed for '97s and earlier 2 WDs, a speedometer interface unit that utilizes the differential sensor for the ABS.

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I also procurred a transmission crossmember from another TDR member and had it modified prior to the NV4500 removal. Essentially the mount has to be 1 1/2 inches lower and 3 1/2 inches to the rear of stock.

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Crossmember bottom.

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When trying to slide the G56 forward it became apparent that the floorboard was interfering with sliding the input shaft into the PP hole. We put a jack under the front of the engine and lifted the front as much as possible to tilt the engine, yet that still wasn't enough. The square part where the shift lever bolts on was still hitting the floorboard. A little sheetmetal work was required.

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After that it was a normal installation and with the transmission in place there is plenty of space on top.

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With a new set of metric bolts and a couple adapters I added the Fast coolers that were on the 5 speed. I fashioned a piece of 1/8 aluminum to cover the hole I had cut. The transmission didn't come with the orange boot for the shifter or a vent so I used the vent from my 4500 along with a formed hose from a HELP package. I bought the boot from an ATV dealer, Moose part # M9206801

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Due to pure luck I dodged a bullet when I had the driveshaft modified. I waited until the transmission was in place, then measured from the flat surface of the flange to the center of the holes where the support bearing is mounted. Mine was required to be 3/16 longer (46 1/2 inches) than Eric's due to a minor difference in manufacture. This measurement is critical since there is no longer a slip yoke.

 

Mission complete.

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That is beautiful. At the risk of oversimplifying the install, it seems like the crossmember/tunnel work is the only real hang up? Everything else then seems to bolt up pretty straight forward. How would the 4x4 differ, if you know. Would the transfer case bolt up to the back of the G56 after the removing the flange?

How are the gear splits now? I am jealous.

Thanks for the pics and the insight. This is my next major upgrade when my stock clutch gives up.

 

I have never seen a 4X4 G56, so I don't know. If the transfer case from your NV4500 would bolt up that would be one method. Either way you will need to get the driveshafts modified I believe.



Actually the only real hangup was sliding the transmission under the truck. A lift would have been really nice to have. The bellhousing is about 19 inches tall so putting the transmission on the jack and rolling it under was a non-happening since the jack was 10 inches tall by itself. We ended up sliding the transmission under the truck, then putting the boom of my engine hoist into the driver's door. We dropped a rope thru the shifter hole, tied it to the transmission, then lifted it enough to roll the jack under it. I would never have accomplished that part had it not been for two large, young friends of mine.

 

Sooooo, whats it like to drive???

 

I've only driven it on a short test to Phoenix and back with a little 1700 pound trailer on the way there. Shifts smooth and tight. Nice and quiet. RPMs at 65 MPH cruise are a couple hundred higher than before. I have the first model (AD) with a 0. 79 ratio 6th gear. The other version is the AE. Thses are the ratios of them along with the NV 5600 and NV4500



AD AE NV5600 NV4500

RATIO



FIRST

6. 29 5. 94 5. 63 5. 61



SECOND

3. 48 3. 28 3. 38 3. 04



THIRD

2. 10 1. 98 2. 04 1. 67



FOURTH

1. 38 1. 31 1. 39 1. 00



FIFTH

1. 00 1. 00 1. 00 . 75



SIXTH

0. 79 0. 74 0. 73 N/A



REVERSE

5. 74 5. 42 UNK 5. 04



Hopefully I'll soon get back to work and get a chance to tow something heavier. I have a small incision on my belly from an umbelical hernia repair that has to heal.

 

Congradulations! Great write up. May you have many trouble free miles.



I still ponder the difference in our trucks that you had to cut a larger hole and mine was tight but it slipped in. You did remove the shift tower (4 yellow painted torx head bolts) not just the lever?



Double check the driveshaft flange to transmission bolts, mine loosened up after a couple thousand miles pulling the GN trailer.

 

I slid the transmission under the truck and then lifted it onto the jack.

 

Oh yes, there is no way it would have gone in with the little shifter stub still bolted in. I think the motor mounts are installed a little different than yours. After we had torqued down the bellhousing bolts I installed the nuts for the mount. I actually pulled the rear of the transmission down about 1/8th of an inch to the crossmember.



Thanks for the tip on the flange bolts and thanks again for all your help.

 

Excellent write-up with pics! Congrats on the conversion!



Do you notice it taking any longer to complete a shift than the NV4500 (due to larger flywheel, etc. )?



Also, can you elaborate a little more on the speedometer adapter setup?



Thanks,



CTD12V

 

Gary,



Very impressive piece of converting, tip o' the hat to you and your team.



Q. Just curious, did you put the bell housing on the old transmission and compare from the front face of the B/H and G56 to the spline range and pilot bearing range so the shaft was confirmed to be in the proper area of the clutch and pilot bearing?



That's keeping a '97 alive and up-dating the gearbox for sure.

 

The act of shifting between gears seems pretty much the same timewise.



Here are the notes that Eric posted which solved my delimma of changing to a 6 speed when NV5600 conversions were popular.



"I finally got around to ordering the Dakota Digital SGI-5 speed signal interface. It works great, simple 4 wire install. Power, ground, signal in (from ABS) and signal out (to speedo)



For anybody doing this conversion, you want to use output #3 (8000ppm ac output)with switch #3 and #4 up.



For my '97 got the ABS signal from the OBD data link connector (red wire with violet tracer) The factory speedo signal wire (white with orange tracer) was found in the big white wire connector that is under the dash in between the clutch and parking brake pedals. "



The picture shows the Dakota unit and the four terminals used. I tried the wires from an old depth finder wire harness that are pictured but the small gauge wire would not stay in the clamp style termials so I went to some higher gauge wire. According to the guy from Dakota a 2 amp fuse is all that is needed in the power wire, so small gauge wire is sufficient.



The dakota came from e-bay.

 

No, because Eric had done the conversion and it worked for him. He sent me pictures of his crossmember and I modified the reinforcements, but other than that everything was identical.



Thank you and CTD 12V for the kind words.

 

Thanks for the info, Gary. That Dakota Digital setup just got the wheels to turning in my head as to the possibility of splicing it inline on my '98's speedo pickup and using it to correct for my different size tires. Looks to be somewhat cheaper than something like a TruSpeed recalibrator. Just not sure if it would screw up the ABS controller or anything. Guess I need to go look at the wiring schematic in my FSM.



CTD12V