’99 Ram manual transmission - rebuild or replace

The NV4500 on my 1999 2500 let go this week. Most likely a bearing out on the input shaft, or possibly the counter shaft. Looking for experiences. I could rebuild this transmission, or replace it with another NV4500, or replace it with a one of the various 6 speed units. Whatever I do I will be doing myself. The only complaint I have about the NV4500 is the 1000 engine RPM jump between 3rd and 4th, which is why I’m considering a 6 speed. Lack of oil ultimately killed this NV4500 so it is not that the NV4500 isn’t tough enough. Are parts still really hard to find for the NV5600 or has that changed?

 

No question for me - 6 speed is the way to go.

 

Agreed. I would opt for the G-56, two gear choices to better match your rear axle gears and a lot longer build span. Lighter weight and parts are more plentiful. 2nd to 3rd on a 5spd is also painful.

If yours was run low on oil I would not even open it up.

 

The 2-3 shift never bothered me. Enough power there that being out of the peak power band wasn’t a handicap. 3-4 was a different deal though.

6 speed anything seems hard to find.

For those that have G56 6 speeds - a question. I have a 3.54 axle ratio. Which G56 ratio will play nicer with my axles? I would like the highest OD ratio I can get. If I am towing heavy I want to stay in the 1:1 direct drive gear anyway, 5th on the 6 speeds.

 

@NIsaacs posted this information for G56 ratios in another thread.

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Your choice on not towing in sixth gear, but I always tow in sixth gear (NV5600 with .73 overdrive and 3.54 gears) In fact, on Monday I will be hauling my last load of pavers, gross combined weight of 20,000 lbs. I will be traveling 220 miles which will include five 5,000 ft mountain passes. Ninety per cent of the trip (with exception to some of the mountain passes) will be spent in 6th gear, even when slowing for 45 mph curves. 380,000 miles on this transmission with no issues.

The NV5600 and the Mercedes G56 manual transmissions are workhorses.

- John

 

A little more info. Note the NV4500 reverse ratio, that was for post '97 Dodge trucks. Pre '97 is 5.61.

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NV4500

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NV5600

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G-56

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Little more info on the above trannys.

NV4500 is about 195lbs and rated 460 tq.

NV5600 is about 360lbs and rated 550 tq.

G-56 is about 220lbs and rated 610 tq. AD or 660 tq. AE.

 

Thanks for posting the information above!

So if I am interpreting the ratio charts correctly, any of the 6 speeds would have about a 500 rpm jump in gears 3-4-5.

Interesting to see the torque specs on the various manual transmissions, especially the NV4500. 460 ft lbs would be what the original rating of my Cummins was, in theory mine has been running at 627 since 2007 if the module advertising is believable.

Really can’t complain about the NV4500 I have other than the 3-4 ratio. About 204,000 on it now. At 107,000 the 5th gear nut came off, pretty easy fix. Be interesting to see how my variation of that repair held up. Never gave trouble again at any rate. I did beat on that trans hard at times. There have been some miles running a gross of 32,000; once being a trip from CT to the far corner of IA.

Borrowed a 2011 2500 Chevy gas to pull my loaded trailer home when the NV4500 let go the other day. While it did the job, I was not wowed by it and it was a reminder I may as well keep my Dodge Cummins fixed.

 

The rating ist for constant load, 100% duty cycle.

 

I was looking at salvage G56 transmissions on carparts.com, and I saw quite a number of them were advertised as having cracked cases. What causes these cracks? Collision damage? I’m not afraid of welding those aluminum housings, but I would want to know why the housing cracks in the first place.

 

Back in the day, there was some internet chatter about weak cases. Mostly due to high HP engines such as sled pullers. A girdle was recommended for them. My guess is, the broken cases you are seeing are from the wreck or run low on oil and caused bearing failure, to the point gears would climb each other and spread/split the cases.

https://www.turbodieselregister.com/threads/g-56-transmission-torque-girdle.228429/

This is a customers Getrag 360 out of a 1st gen. It had about a cup of oil in it. Note the front shaft heat/gear damage. The rear shaft is a used one I sourced. The case was spider web broken between the front bearing retainer bolt holes and the bearing pocket on the case.

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Early on, in some high HP/high torque pulling trucks, we saw some damage to the G56's at the truck shop I worked at. Our transmission guy theorized it was from the long shafts in the transmission without a center support, too much flexing. I can't recall if it was case damage or gear/shaft damage. We saw many NV4500's with 3rd torn out of them and NV5600's with seized pocket bearings. I don't think there's a perfect transmission out there. I don't think we ever saw any issues with the ZF6, but there weren't any Fords putting out that much torque....

 

I’m just wondering if I should pass on transmissions with cracked housings or if it is something that can be dealt with.

I am aware of the failures related to high hp, but I don’t plan on making huge hp with my pickup. I want to keep the power levels where I can use all of the hp all of the time and not worry about engine or driveline failures.

Thinking about how my NV4500 acted after the failure, I am betting it is an input shaft bearing out.

 

I have the AD version of the G56 and it has served me well. I have had it for about 700,000 miles with one input shaft bearing failure. I have towed a LOT of heavy trailers with it, now I just pull my 5th wheel with my bass boat behind it. I wouldn't touch a damaged case transmission. If welding them was not a problem they would be welded before being offered for sale. With the 6th gear ratio of .79 I am turning about 100 more RPM at 60 mph than I did with the 4500. I have a 3.5 differential. If I had a choice between the AD and AE I would take the AE. I didn't know there were two versions when I did my swap.
Engine/Transmission (1994 - 1998) - Mission: G56 (pictures) | Turbo Diesel Register

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

 

Tempting as it is to swap I may end up fixing the 5 speed given the time and cost to put a 6 in. In any event nothing will happen until this winter most likely. Harvest season is here and I will be busy custom baling until Thanksgiving hopefully. And I will be running another fall without a pickup. Last time it was the injector pump that crapped out just before harvest.

 

Subject of the discussion. #ad

 

Gearclash: I have an off-topic question. When you fold your side mirrors back, like to drive thru tight spots, do they whack the sheet metal on the doors? I ask this because I have Cipa slide-out replacements on my 1996. When they are folded in, it is possible for them to hit the door sheet metal and leave a dent. In fact, they have done so. And I am fixin' to get the truck repainted and the dents un-creased. I don't want to get new dents, and if new mirrors will do the job, it would be good.

Nice truck, by the way.

 

If I was swapping in a G56 for towing I would want the AD ratio behind a 5.9. Aside from 5th the ratios are all lower than AE and better suited for towing, especially with a 3.54 rear end.

Which version of then NV5600 was that?

It was bolted to a HO CR for a couple years with up to 610lb/ft and no issues.

I ran mine at around 1000lb/ft at the crank and the trans didn’t complain, but it did take a different clutch.

 

I agree with the AD and 3.54's. My '01 would be awesome with it.

The transmission ratings I pulled of the internet, so....

However, it is not unusual for a manufacture to over power some ratings down wind of the crank.

My NV5600 has 365k miles on it with about 400/900 for years.

 

These mirrors clear the body completely when folded. Never had them touch. I’m not sure who exactly made them; they are not OEM.