Engine/Transmission (1994 - 1998) What was a 5spd is Now Only a 4spd

[MStearns]

Well I now know what my summer project is going to be whether I like it or not. Lost Overdrive on my way back from the family farm today. So the research begins... Repair the NV4500 or upgrade to the NV5600



I've always wanted a step between 3rd and 4th but parts support for the 5600 has me concerned.

 

[snappy]

I have both. The 3 to 4 on the Nv4500 is best handled with a GSK. It helps with towing. I like 'em both. Lost 5th twice before doing the fully splined mainshaft.

 

[gitchesum]

I'd lost my 5th gear nut twice on my 97. I just went with the $30 upgraded nut and pulled the tail section off and repaired it each time. It would last about 35,000 miles or so, just about the time I would need to change the fluid.

I figured for the cost of the nut, plus a little time, I would have to replace that 5th gear nut quite a few times to justify the cost of the fully splined shaft.

 

[HBarlow]

Why not a G-56? Parts support should be available for the G-56 for many years into the future.

See GAmes' recent posts detailing his conversion of NV-4500 to G-56 in a '97. According to Gary the conversion is fairly simple and easy to perform.

 

[MStearns]

From what I've read, a 2" body lift is required for a G-56 in a second gen truck and I have no desire to make my truck any taller than it already is. So increasingly it is looking like a NV5600 or repairing the 4500 and adding some kink of gear splitter.

 

[hsmith]

Pretty sure Gary didn't lift his for the G56 swap.

 

[GAmes]

From what I've read, a 2" body lift is required for a G-56 in a second gen truck ... ... ...

You don't read enough.

https://www.turbodieselregister.com...on-1994-1998/221115-mission-g56-pictures.html

 

[MStearns]

Ahhhh... reading and remembering... two very different things

 

[MStearns]

A little tin work is easy... But the gear ratio's of the the first generation G56's are not what I'm looking for. Does anyone have a source for a second generation G56 with the higher OD? I wonder if it something as simple as a gear swap to get the higher ration OD??

 

[GAmes]

At 65 mph I am only turning 100 more rpm than I did with the 5 speed(now it is 2100). I could easily get it back by going up a tire size. Turns out that I am getting as good mpg as I did before, sometimes better.

 

[paulsmith]

I have a stock 98 12 valve, I have pulled the trans more times this year than I changed oil! The trans is being "rebuilt" from re-manufacturer in Kentucky. Stock truck but at about 3000 miles, just cruising down the road, it just falls into neutral--- no more 5th.

I would fix it myself, but it is still under warranty.

was told a snap ring fell off the shaft last time... . (4 weeks ago)

Problem is my lost time and dumping out the syn oil (and shipping cost) to send the trans back every few weeks.

This will be the 4th trans in the truck since January...

 

[MStearns]

I haven't entirely decided yet, but after several nights of research I think it boils down to tow choices... Fix the 4500 and add a gear splitter or swap in a G56.



All things being equal I would really prefer to have a gear splitter. Not only would it fix the step between third and fourth but would provide the oportunity to split all of my gears. And the ability to run 4th over when towing or Double over when cruising is really appealing. But after crunching the numbers this is going to be more expensive by about a thousand bucks and the reliability of the Gear Vendors unit, particularly backing up heavy loads, is troubling. More stuff to go wrong.



So as it stands, I am leaning toward a G56 swap. Although the aluminum case gives me pause my real concern is parts support. Who is to say this transmission isn't discontinued like the NV5600. A quick search of the internet for parts for the G56 doesn't turn up any thing but clutches. These trannies have been around quite awhile now... Where are the rebuild kits???



As I said I haven't entirely made up my mind but need to do so in a hurry so I can get my truck fixed ASAP.



Thoughts??

 

[GAmes]

The latest TDR mag has an article about the G56. Standard Transmission in Ft. Worth can answer your questions about parts. If you decide to go with one I have a trans crossmember you can have for the cost of shipping, plus the template for the steel plate.

 

[MStearns]

The crossmember offer sounds fantastic... Is there any difference between the 2wd and 4wd crossmembers?

 

[GAmes]

The crossmember offer sounds fantastic... Is there any difference between the 2wd and 4wd crossmembers?

No, in fact the one I have came from a 4wd. It had a bracket or two that I discarded. I installed it, modded mine, then did the swap. I'm on my way to Great Falls, Mt right now and possible to VA from there but should be home by the 12th or so. If you want it just let me know.

 

[MStearns]

Pulled the trigger on an 09' G56 with only 28K on it from an auto recycler for $2600+$250 for the core!! Also have a new clutch from South Bend on the way. Now need to start looking for a good driveline shop in the Omaha area.



GAmes I will absolutely take you up on the crossmember offer! No worries regarding your schedule I am just gathering parts now. I won't be able to get started on this due to my own schedule till after the 4th. I'll send you a PM with my contact info.



I do have a couple of quesitons regarding the swap...



1. Is an adapter or spacer required for the G56? The guy at South Bend thought a spacer would be required due to differences in the length of input shafts between the G56 and the NV4500. If so where can I get my hands on one?



2. Also, what model year shifter and boot will I need??



3. From everything I've ready my transfer case should bolt right up. Can anyone confirm this or will an adapter be required???



4. With less than 30K miles on it do you think it is worth opening up and inspecting the syncros, etc... prior to installing it????

 

[ewcmr2]

1. Is an adapter or spacer required for the G56? The guy at South Bend thought a spacer would be required due to differences in the length of input shafts between the G56 and the NV4500. If so where can I get my hands on one?

2. Also, what model year shifter and boot will I need??

3. From everything I've ready my transfer case should bolt right up. Can anyone confirm this or will an adapter be required???

3. With less than 30K miles on it do you think it is worth opening up and inspecting the syncros, etc... prior to installing it????

#1 Garys and mine are working without any adapters. South bend SMF and clutches.

#2 G56 shifter with my OE '97 boot. The boot is a little short and sometimes slips off the round section of the shift lever. If the late model shift boot is taller it would look/fit better.

#3 The G56 is clearly set up for a tranfer case to bolt to it. Mines 2wd so I can't confirm what is needed to make it work.

#3b The fluid that dumped out of my 70k G56 looked like new. At 30k I wouldn't worry about the internals. I'd change the fluid as cheap insurance and to know it's not contaminated in any way.

 

[MStearns]

Outstanding!! I'll have to call the auto-recycler where I'm getting the transmission from to see if they can include the shifter (I forgot to ask about it when we were talking about the transmission). Then it sounds like I'm set, just as soon as I find a place to do the drivelines.

 

[GAmes]

One good thing about my sheetmetal work was I wasn't limited to the stock hole in the floorboard. With the stock boot about 3/4 inch forward it doesn't come off the shifter.



After I bought mine I took it to Standard transmission in Ft. Worth. They spun it in all 7 gears with a large drill that had a spline adapter on it and pronounced it serviceable. I'm sure you could rig up something similar if you have any doubts.



When you are talking to the recycler see if you can snag the front portion of the doner's driveshaft. It might be the right length, and you would have the right flange.

 

[MStearns]

Good call I hadn't thought about the front drive line being the right length. I'll check to see if the American axles use the same size U-joint as the Dana.