G56 vs 68RFE

[RVTRKN]

What is your duty cycle in terms of GCVW, and the average weight? Also, can you let the clutch out slowly without giving it any throttle like you can with the NV5600? Did you replace the DMF, and if you did how do you like the difference between the solid and the DMF. I see in your sig you have lots of miles and experience in the NV5600, and is the reasons for so many questions.



Thanks Steve

 

[Barry]

I loved the 5600. Never liked the G56... ..... only because of the gearing. I can go from empty to 23 to 24K on GC weight. Most of the time, it is 12 to 16K... ...



I can let the clutch out without throttle. But I am testing prototypes not available to the public yet. The DD I am testing now is a monster. Stronger than a garlic milk shake. Other than that, I am not at liberty to discuss it.



I have never put this many miles on a single pick up before. It has been an interesting ride... ... ... ..... At 230K, I still have the original brakes. Love the BD exhaust brake.



Hope I have answered your questions... ... ... ...

 

[RVTRKN]

Barry, do you still have the DMF?

 

[RVTRKN]

My opinion is the same as yours, the NV5600 over the G56 would be my preference as well as everybody else's I imagine. But they are expensive, now that they are out of production. I've looked into replacing the G56 with a Eaton Fuller 6 spd, if my G56 ever grenades itself. PM me, if you would like the little bit of research info, I've done so far. It can be done, but then you would need to find adaptors, in which thats were my research has been focused on so far.

 

[Barry]

No the unit I am field testing now is a single solid flywheel of Perfection's design. The prototype clutch is a double disc.

I am due for a change out at Perfection next week. It is a single disc with super clamping power. They are also changing my hydraulic system to an all metal design. Their hydraulic system is great. Feels like a real truck clutch and not a Dodge Neon. My wife hates it.

 

[AEdelheit]

RVTRKN: Just an FYI the ECM on your truck should throttle the engine if it gets below a minimum RPM (750 idle) so you should not have to give the engine any throttle to start, I had 37" tires 3. 73 gearing and could easily start in 2nd unloaded and 1st with a 12k trailer, that was with an older South Bend DD 3250. Not trying to say you dont know how to drive a manual transmission but you may want to look into why your engine doesnt throttle itself below idle speeds.

For what its worth I replaced my clutch at 50k miles, at the time the DMF was fine but Valet parking in Chicago decided to destroy my clutch so I limped it to South Bend and had a new one installed, untill then it was functioning properly.

 

[Barry]

I have one of the early G56 trannies. It is the low ratio gearing model. Like running around with 4:10 gears. So, if empty, I typically use 3, 4 and 6th when empty.

 

[AEdelheit]

I could see that, starting in 2nd with 37's was easy so with stock tires ya not even funny. Actually a buddy of mine started my in 4th one time when it still had the stock tires with the Edge juice w/ attitude, was kinda funny, he had a 22RE yoda and hes like "huh, starts off the same as my yoda, I thought it would do better" I looked at him and said that that was 4th, the look on his face was priceless!!

 

[RVTRKN]

I could see that, starting in 2nd with 37's was easy so with stock tires ya not even funny. Actually a buddy of mine started my in 4th one time when it still had the stock tires with the Edge juice w/ attitude, was kinda funny, he had a 22RE yoda and hes like "huh, starts off the same as my yoda, I thought it would do better" I looked at him and said that that was 4th, the look on his face was priceless!!

RVTRKN: Just an FYI the ECM on your truck should throttle the engine if it gets below a minimum RPM (750 idle) so you should not have to give the engine any throttle to start, I had 37" tires 3. 73 gearing and could easily start in 2nd unloaded and 1st with a 12k trailer, that was with an older South Bend DD 3250. Not trying to say you dont know how to drive a manual transmission but you may want to look into why your engine doesnt throttle itself below idle speeds.



For what its worth I replaced my clutch at 50k miles, at the time the DMF was fine but Valet parking in Chicago decided to destroy my clutch so I limped it to South Bend and had a new one installed, untill then it was functioning properly.

It won't stall every time I start out like I did with my NV5600, sometimes it seems to have a mind of its own. My NV5600 could pull my boat up the ramp just by letting out the clutch in second, and my daughter just about knocked me out of the boat one time when she dumped the clutch, and even then it didn't stall, but you can imagine the look on her face when she did it. If I'm at a an intersection were it has a slight upward slope is when I can depend on it stalling without giving it throttle. When I test drove my first G56 it did the same thing when entering the street which had a slight incline. Due to that, I figured it was normal when I took delivery of my C&C and it did the same thing at the same place, and that was without the bed. I can start out in 1st but that gets old quick. And its not in the gearing, look at sig, and its not the early version of the G56. I was driving both at one point and hated the difference because there is a different style between them both and would have to get used to whatever truck I was driving for the first mile or two, even were the clutch would engage at was different.



I will try slipping the clutch a little longer without throttle, just to see what happens.

 

[bartco]

finally lost the 68RFE at 280,000 miles in 2011 3500. towing heavy construction trailers 50% of the time and always loaded with 1000 lbs+- tools and 4 occupants. not cheap to replace but cant really complain with that many miles. changed fluid every 25000 miles+-

 

[RVTRKN]

Thanks for bringing this old thread back, I can see my opinion of the G56 has changed over the years. Yes it cost a lot to convert from a DMF, to the SMF, but the holding power of the DD3250 with my issue I have of the regen surging issue, has not slipped even at 23K GCW. I did drive a 2014 68rfe equipped 2500 for 20K+ miles and hated it, but it was with the 3:42 rear diff. Knowing what I know now about the two transmissions, I'd still pick the G56, but the day I took delivery of it, I'd install my transmission cooler setup and change the oil to Mobil Delvac Syn 50 fluid. If I had to chose between the G56 or the Aisin, I'd pick the Aisin with 4:10 diff.

 

[EB]

I'm getting close to 650,000 miles now and just did a transmission service last week. Just filter and fluid, no metal on any of the magnets just the normal "fuzz". Not having any problems with the transmission at all.

 

[AKetay]

I tow commercialy and have had a few trucks, see signature. I really liked the NV5600 with SMF and lo HP motor. The 09 was a complimentary setup with DMF. More power and factory exhaust brake. The G56 made it to 356k miles only having to replace the silicone shift boot that cracked over time and use. The DMF was replaced at 171k miles because of broken springs, throw-out bearing and friction was still in good shape. Replaced with South Bend SMF conversion. Truck is still going with over 430k miles, no problems. Next truck, 2012 with 68rfe was a gamble for me. I liked the automatic for most of the towing I do, but when it came to heavy loads it was a different story. Did not like the gear hunting on little rolling hills in the southeast US. Steep short hills in the northeast US presented problems going downhill. Did not like the hard downshifts with heavy loads in good weather, would not do it in bad weather. Out west in the mountains it was a totally different truck, transmission worked well with long grades. Maintenance wise it was better than I expected, 423k miles before I had to have shift solenoid replaced at $1100. Just a little less than previous truck clutch. Overall mpg with automatic was not as good as manual which prompted me to replace it at 437kmiles with newest truck. Love the fact that I have manual again. Only thing that concerns me is the new gearing, 3.42 rearend and taller tires with taller sixth gear. Time will tell, but I do like towing heavy again.

 

[Regcabguy]

I could see that, starting in 2nd with 37's was easy so with stock tires ya not even funny. Actually a buddy of mine started my in 4th one time when it still had the stock tires with the Edge juice w/ attitude, was kinda funny, he had a 22RE yoda and hes like "huh, starts off the same as my yoda, I thought it would do better" I looked at him and said that that was 4th, the look on his face was priceless!!

I drove a Honda CRV manual awhile ago and had to think about throttling it in order to not stall. As stated I just let the clutch out on my G-56 and away it goes. I've stalled the truck on a miss shift in 2006 and that's it in all these years. The TDI's are the same. Diesels just lend themselves to a manual trans.

 

[RVTRKN]

I tow commercialy and have had a few trucks, see signature. I really liked the NV5600 with SMF and lo HP motor. The 09 was a complimentary setup with DMF. More power and factory exhaust brake. The G56 made it to 356k miles only having to replace the silicone shift boot that cracked over time and use. The DMF was replaced at 171k miles because of broken springs, throw-out bearing and friction was still in good shape. Replaced with South Bend SMF conversion. Truck is still going with over 430k miles, no problems. Next truck, 2012 with 68rfe was a gamble for me. I liked the automatic for most of the towing I do, but when it came to heavy loads it was a different story. Did not like the gear hunting on little rolling hills in the southeast US. Steep short hills in the northeast US presented problems going downhill. Did not like the hard downshifts with heavy loads in good weather, would not do it in bad weather. Out west in the mountains it was a totally different truck, transmission worked well with long grades. Maintenance wise it was better than I expected, 423k miles before I had to have shift solenoid replaced at $1100. Just a little less than previous truck clutch. Overall mpg with automatic was not as good as manual which prompted me to replace it at 437kmiles with newest truck. Love the fact that I have manual again. Only thing that concerns me is the new gearing, 3.42 rearend and taller tires with taller sixth gear. Time will tell, but I do like towing heavy again.

You need to look into my custom G56 transmission cooler, I maintain my trans temperature at no more than 180*, any higher than 180*, I turn the pump on and it cools to @160* easy.

,

 

[EDankievitch]

I've been lucky enough to have owned trucks with both the G56 and the 68RFE. If I was to order a truck today it would be a manual. Not that I hate the auto it works and works well. I miss havint the controll I had with the manual. I drive down the same hill every day each day and the auto will not do the trip the same two trips in a row. one trip it'll stay in the lower gear and the engine break works the whole trip. the next time it'll up shift and then un lock and I've got to ride the break the whole way down. While it's nice in traffic and to have the extra power, manuals are de- tuned a wee it. When you are the one driving the truck it just feels right. I got 137,000 miles out of my first DMF clutch. It worked and worked well. The South Bend I replaced it with worked well as well. I had about 100,000 miles on it when I traded the truck in. In hind sight I should have never traded that truck in..... was an 05.

 

[RVTRKN]

The auto will not do the trip the same two trips in a row. one trip it'll stay in the lower gear and the engine break works the whole trip. the next time it'll up shift and then un lock and I've got to ride the break the whole way down.

My 68rfe did the same thing, so I would manually shift it into 4th with the EB in the ON position and it would work every time. In drive it was hit and miss, and you would never know when it would not engage the EB. Your G56 had the higher gear ratios which is actually better than the newer lower ratios. Yes it seemed to run at higher RPM's, but its easier on the trans and wont run as hot. Mine has the lower gear ratios and runs almost identical as my NV5600 did, per the final RPM in 6th gear at 2050RPM @70MPH. But it does run hot without my cooler setup.