G56 Update

[Joseph Donnelly]

Each manual transmission has its weak points, and I have discussed them in the TDR magazine. The weak points are often found when the truck is used for heavy hauling, towing, sometimes beyond mfg. recommendations. Sometimes with a lot of power adders. I prefer to overbuild the driveline if significant weaknesses have been found, even though I won't push mine to the limit. "If you llike your G56, you can keep your G56." I'd like to see someone who believes his G56 with 100,000 miles on it is good and hasn't been overworked take it to the rebuilder, such as Std. Trans. and have them check the case for stretching, and the bearings for overheating and browning. People generally wait for catastrophic failure before rebuilding the trans; I didn't with my NV5600 and it was instructive to see what was good and what was marginal with it.

 

[RVTRKN]

I have posted pictures in the past with browned bearings that were replaced on my G56, and there was only 35K miles on it, and I can count on one hand how many times it towed at close to the GCVWR, but never over that. So much for towing over the GCVWR causing the problem as well at stock power, there is no Programer on my truck.

 

[Regcabguy]

From what I have read parts for the NV5600 are somewhat hard to find due to the short production run. They are supposed to be pretty pricey too. My 12V had the 4500, fabulous transmission. The truck had 240,000 miles with the original clutch and zero issues with the trans.

I wanted a manual with my new truck but after test driving the Aisin, no brainer. After 10,000 miles still very happy with it. Pulling the 5th wheel I no longer have to "drive" the truck ie: watching for hills, etc. I am more along for the ride. Love it.
kk

Blumenthals stated to me on the phone that they manufacture NV5600 internal parts in house. That was a couple of years ago.
I love the G-56. Just wish it had an iron case. My truck and wet camper total 8900# wet with two occupants. Camper's always on. Smarty's been on there from the 2nd week. My fluid aside from my 45 mile experience with GJ always comes back clean. That's not to say the trans is not smoked internally,but it gives me no indication of that from shifting or fluid condition.
That being said if I win the lottery and bought a new one it would have an Aisin.

 

[Newsa]

g56 updates

http://www.dieselhub.com/trans/G56.html
G56 is used in Mercedes medium duty trucks. That's good enough for me. The manual transmission was why I went with RAM

 

[Newsa]

All DMF's fail early in the life of the G56, that's a fact, so there's $2K, then transmission inspected by a competent shop, so there's a $1k (browned bearings in my case and most likely others as well if not filled a quart over) and then the cost of protecting the aluminum case, in my case, $700.00, if you install the Girdle, that's a $1K. This is my reality, and with only 35K miles at time of DMF replacement. Now I have a noisy transmission, and even though I'm told that's normal and not to worry. My 40+ years as a mechanic just can't get used to the rollover noises at low RPM, I'm not including the dual disk clutch that makes noise as well, that I elected to have installed.

The cost of the Aisin transmission option $2K

Did the transmission fail at 35k with factory fill ATF4+?

 

[RVTRKN]

Keep in mind that the original G56 was geared alot lower and the medium duty trucks wasn't geared for light duty application, probably 4:88's or higher. The only advise I can give the G56 truck owner is to install a temperature sensor and drop a gear if it starts to warm up, especially a 3:42 optioned truck. My 3:73's with the AE G56 might have something to do with it running hot, but before my cooler was installed, I was running in sixth with 15K GCVW (boat in signature) going west out of Palm Springs on I10 and recorded 230*. They run hot and as mentioned I have the browned bearings to prove it. Unfortunately I did not have a temperature sensor installed, not until the trans was inspected and the bearings replaced and the SMF installed.

 

[Newsa]

I always thought the lubricant would burn before the bearings would brown. Learn something new every day

 

[RVTRKN]

I didn't see the old oil when it was torn down for inspection, but the bearings were browned and with only 35K miles. I went through the extra expense of having it inspected because of the complaints that they get noisy with the SMF. So I had Richard at Standard Transmission in Tucson Az inspect it so I would know the noise I would be hearing would be normal.

 

[RVTRKN]

Here's the pictures, its hard to see the brown on the bearings, but you can see it in the races. This condition was not caused by abuse, over GCVWR or programing, and only 35K miles on the trans. So its hard for me to think this transmission is up to the task behind a CTD.

 

[wiley75]

Funny how on the internet a "problem" can be created when their really is no problem at all.

 

[RVTRKN]

$1800.00 SMF/Clutch kit, $1400.00 Labor, some internet problem. It's a well known fact the DMF will fail, period. OK, so this will be my last post on the subject, unless someone asks my opinion, otherwise everyone can bury their head in the sand. If I were purchasing a new truck it would have an Aisin Auto, and this comes from a a manual transmission fan. If my truck had the NV5600, this post wouldn't exsist. GOOD LUCK with your G56's.

 

[MCSloan]

I agree 100% with RVTRKN. My DMF failed at 38000 mi. Replaced w/SB/Clutch kit. Transmission temps would run around 230 to 250 after 4 or 5 hr run towlng 15000 lb trailer W/2007 3500. Transmission noisy at those temps. Finally at 65000 mi got rid of truck before major problems and bought a 2013 W/aisin. My first auto ever . Am very happy with the aisin and temps run 165 to 190 under same conditions. The G56 just can't take steady heavy towing IMHO.

 

[Newsa]

Each manual transmission has its weak points, and I have discussed them in the TDR magazine. The weak points are often found when the truck is used for heavy hauling, towing, sometimes beyond mfg. recommendations. Sometimes with a lot of power adders. I prefer to overbuild the driveline if significant weaknesses have been found, even though I won't push mine to the limit. "If you llike your G56, you can keep your G56." I'd like to see someone who believes his G56 with 100,000 miles on it is good and hasn't been overworked take it to the rebuilder, such as Std. Trans. and have them check the case for stretching, and the bearings for overheating and browning. People generally wait for catastrophic failure before rebuilding the trans; I didn't with my NV5600 and it was instructive to see what was good and what was marginal with it.

I see many recommending Standard Transmission. My only previous experience with a transmission rebuild was at a shop in Miami where nobody spoke english (Spanish only). I think they gave the tow truck driver a kickback. Is there only one standard transmission location?

Or are there several?

 

[Joseph Donnelly]

The supervisory transmission man at the Fort Worth TX facility semi-retired to Tucson AZ and subsequently started a satellite facility there. So, there are two facilities for Std. Trans. and Gear Co.

 

[Deleted member 995608]

I've read several horror stories where the G56 failed early and then continued to be problematic after each consecutive rebuild. I wonder if this is due to a stretched aluminum case? One has to factor in the possibility of a bad rebuild by am incompetent mechanic but if the failures continue, I'd have to assume the case is stretched and no longer holding its tolerances.

 

[Regcabguy]

I believe it was mentioned in this publication that Standard considering cloning an iron case for the G-56.
Heck,I'd settle for a 60+ hp dmf that could handle my popup for 100K. I think it cushioned the trans,but was under engineered. Wouldn't be appropriate for the heavy haulers but for us average guys it would be a gem.

 

[RVTRKN]

I agree 100% with RVTRKN. My DMF failed at 38000 mi. Replaced w/SB/Clutch kit. Transmission temps would run around 230 to 250 after 4 or 5 hr run towlng 15000 lb trailer W/2007 3500. Transmission noisy at those temps. Finally at 65000 mi got rid of truck before major problems and bought a 2013 W/aisin. My first auto ever . Am very happy with the aisin and temps run 165 to 190 under same conditions. The G56 just can't take steady heavy towing IMHO.

I'll reply to this as an answer to the overheating issue, see pics.

not anymore, as my trans runs cool now.

 

[MCSloan]

RVTRKN Thats a very nice set up.I had thought about doing something similar but had 2nd thoughts about what might be the next weak point. After DMF and heat problems along with problems with a GV4500 in a 1996 3500 i decided to put my money towards a 2013 W/Aisin. i am a little gun shy when it comes to these manual units. Don't think they are up to handling the torque of the cummins. Hopefully the Aisin will hold up better. Time will tell.

 

[RVTRKN]

Well I changed the oil to 100% Mobil Delvac synthetic transmission Fluid 50 in my G56 and like it so far. The trans is much quieter and at 170*F at idle is 75% quieter. Before the change, at idle, the noise was louder than the cummins. With the last oil I used, when cold, it was at it should sound, but 5 minutes of idle, the marbles came back. Now it sounds quiet at idle, and seems to shift into reverse easier. BTW, I found the MDSTF-50 at 55.00 a gallon. http://www.zoro.com/i/G3165267/

 

[STEVEBROOKS]

rvtrkn: I'm very interested in adding a trans cooling set-up to my truck like yours. How has it worked for you so far? Any add'l info you can provide (ie, more photos/part numbers/advice/etc) would be greatly appreciated.

Thanks,

Steve