Looking at buying a 2005 Cummins and want the 6 spd, what is the difference between the two option, I think the hd gives you the 11.50 rear but what do i know, please help.

 

There is only one manual transmission with the Cummins engine, the G56.

The NV5600 started the 05MY builds, but they switched to the G56 mid model year (they weren't ready with the G56).

Both are HD transmissions.

 

so after looking after some 300 2500 on the internet how come some say HD 6-spd and some say 6-spd

 

Who ever is advertising doesn't know his a$$ from a HD 6-spd

 

You could still get the NV5600 in the 05's. That's what they are calling the HD 6 speed. There was one on the lot when I bought my truck this weekend. The G56 is much more common on dealers lots right now and It's the only choice for the 06's.

The NV5600 is a $400 option over the G56.

 

as far as I know any truck that has the 600 or 610 engine has the 11.50 differential. as for transmissions, the NV5600 was offered at the same time as the G56, the NV5600 being sold as the heavy duty, then eventually it was phased out & G56 is the only one available now. still may be some NV5600's left on the lots easy to tell apart
NV5600- reverse up & right (next to fifth) cast iron case
G56- reverse down & left (next to second) aluminum case
the NV5600 also has a higher overdrive ratio (reduced RPM at highway speeds= better mpg) I would recommend the NV5600 if you can still find one. hope this helps

 

Thanks for all the info found a couple.

 

When I ordered my '03 by seller dealer (good, trusted personal friend) said that in that model year the only difference between the HD and hte regular six-speed int he 2500 series trucks and higher was that the HD version had a PTO plate and gear whereas the regular transmissions did not.

 

The plant never built with both transmissions.

05 started with the NV5600 and when the G56 was ready they switched.

New Venture Gear is no longer. They had to switch.