I filled up the tranny last night with MTF and drove it this morning. I noticed the 2nd to 3rd gear notchy shifting is reduced and the 4th to 5th gear notchy shift is gone when the tranny is cold. Shifting feels much smoother now. I had about 5k miles on Pennzoil Synchromesh for the comparision. I haven't used Redline MTL so I can't comment on that lube.

MikeyB

 

how do you know what 6 spd you have? mine is a 2005 with 70k on it. changed fluid at 25k and 56k with napa synthitic and it is so stiff you can hardly chane gears. will a different fluid help? seems like it is the top of the shifter that is hard.if you put mine in neytral and pull it over between 1 and 2 and let go it wont even return to center. seems like it is beter in the morning when its cold. any ideals would help.

 

PLASTICMAN-

1 3 5 R
2 4 6 . or rusty steel housing=NV5600

. 1 3 5
R 2 4 6 or aluminum housing=G56

Changing the brand of oil will help, so I have read, mine has about 25000 miles (NV5600) and not changed it yet, not yet decided

About the stick not moving back between 3-5 in neutral, never seen that before, if you still have warranty I'd say take it in, without the quadzilla installed

 

Plasticman,
I bet the NAPA lube is too thick for the tranny if shifting is really hard. The NV5600 uses a special 5w-30 GL4 lube. The lube can be found at GM/Mopar dealers and Pennzoil/Quakerstate Synchromesh at auto parts stores. GM carries this lube for the NV3500. For synthetic go with Redline MTL or Amsoil MTF.
If you have the G56 tranny it uses ATF+4.

MikeyB

 

I finally got my Amsoil MTF the other day-there was a backorder on it. In changing out the old oil I drained 4 US quarts and put in about 4 3/4. Thought that I'd try to squeeze a little extra in and see if that would help. The shifting is noticeably better than it was before. My previous experience with manual shifting has been primarily with BMWs and Volvos. My NV5600 doesn't shift as smoothly as these, but we are not comparing apples with apples here. I am happy with the improvement and consider the change to be worthwhile. It would not surprize me if the factory was a little short in their fill up. I didn't know what to torque the drain bolt to, so I checked the bolt before I removed it and it did not move until 36 ft lbs, so I torqued it in at 35 lbs. Happened to have a 17 mm hex kicking around and it worked great for removing the fill plug.

 

Can't speak for Amsoil, but I put Reline MTL in and it is so smooth shifting up or down.

 

I have run my nv5600 with a full six quarts of the oem stuff for 160k and it shifts just fine, actually better as it wears.

 

Haulin, do you take the shifter off to get the extra fluid in?
I jacked up the back of the truck fairly high and was almost able to get 5 quarts in mine.

MikeyB

 

This is a older thread but I have AMSOIL Manual Synchromesh Trans Fluid in my 2008 G56, after replacing the DMF of the stock clutch with a South Bend Dual Disc. I have read several threads and posts where several shops who rebuild G56's will not warranty them unless some type of manual Synchromesh is used and they also recommend the one quart over fill for one of the upper bearing. This is a slippery slope to talk about because of the human opinion. I definitely like the way it now shifts and how the noise is reduced once the dual mass flywheel is removed. Just my two cents worth.

 

It's going to be awhile with summer coming on,but I wonder how cold shifting will be? This is the 75-90?

 

No Danderson not the 75W-90, what I installed is the Manual Synchromesh Transmission Fluid (which is 5W-30). But I agree with your questioning attitude and curious what it will shift like when the weather turns colder.

 

5-30 won't be an issue at all. I used Pennsoil 5-30 for awhile but the tranny was still pretty loud.

 

This thread was initially for a NV5600 manual trans but poster AMSOIL1 is now talking about a G56 manual trans which is completely different.

I'm not a fan of Amsoil and one reason is that they spec their manual transmission fluids on the engine oil scale rather than the gear oil scale.
I'm a fan of Red Line gear oils and they state both specs for their manual transmission fluids and have a much greater selection than Amsoil.

Amsoil MTF Synchromesh is 5W-30 (about 70W-80 on the gear oil scale). It's very thin oil and won't be a factor in cold weather. IMO it's still too thin, barely thicker than the original ATF in the G56 trans.

The next question, is poster AMSOIL1 just advertising for Amsoil??


Is anyone else having trouble posting and the forum won't let me post a picture??

 

Thanks for the info StealthDiesel.
Carl48 on here is a wealth of realworld G-56 usage and fluids. His company tows heavy and racks up thousands of miles on these things.
I'm going to install coolers on mine in the future.
The www.carbonitecummins.com site is extremely helpful also.

 

I have a G56.
Could someone please tell me what fluid comes standard and what will mix with it?
The dealer is crazy! They want $25.00 per quart!
Thanks guys.