Engine/Transmission (1998.5 - 2002) NV5600 & Synchro's

[steved]

None of the additives lasted in my experience... I used Lucas transmission Fix, LubeGuard Gear Oil Additive, and two types of LSD fluid.



I run a mix of Redline MTL and MT-90 with good results... about 25% MT-90 and the rest MTL. I would not recommend it in cold weather, but in warm weather it works well. It has "lasted" better than anything I have used to date (straight Amsoil MTF, Royal Purple synchromax, PZ Synchromesh, and straight Redline MTL).



I might try RP Syncromax and some RP MaxGear next time... just because I can get it locally.



steved

 

[DDrees]

Thanks Steve for your In puts!

 

[Duluth Diesel]

I run the AMSOIL MTF in the NV5600 on my '02. I remember when I first brought the truck to the dealer (bought it new) and the dealer refused to change my NV5600 fluid saying that it would void the transmission warranty and that the fluid was "lifetime fluid. " I told him "that's b. s. " and I left. I've run the AMSOIL MTF ever since and the transmission shifts great. I tow heavy fairly often and the engine is no longer stock, so I'm putting some torque to the trans. I change the MTF every 30k miles to err on the side of caution. NV5600 trannies are getting hard to find parts for, so I figure the cost of frequent fluid changes is worth it. I also fully agree that 6th gear is for marketing, not towing. I run it in 5th when towing or hauling sizable loads. If trucks in stock form are losing 6th gear, then modified trucks when towing are putting a huge strain on the overdriven 6th gear while towing.



-Chuck

 

[blacksheep4x4]

Had the same problem with my 03. I had Amsoil MTF but the problem did not go away until I added the Mopar Limited slip additive. After adding the additive truck shifted like it was brand new.

 

[Texas Diesel]

How many bottles of LSD modifier did you add?

 

[blacksheep4x4]

The Dodge tech told me half a bottle would do it but I just poored the whole thing in.

 

[Silver_Ram]

I still have the Amsoil MTF in the trans w/ Mopar LSD fluid. I haven't had any problems for quite awhile. At the suggestion of a trans rebuilder buddy, I have a case of Amsoil MTG in the garage that will be going in soon. I have Amsoil LSD as well, but I'm going to try the MTG alone first.



I wanted to see the temp difference between the MTF & MTG, but I haven't installed the Juice trans temp probe yet.

 

[PAckley]

I have learned about these trans the hard way. Just replaced trans with rebuild from Standard transmission in Ft. Worth, TX. 2000 trans had 1 1/4" output shaft, I upgraded clutch/flywheel to HO flywheel from Southbend Clutch. Then bought the 1 3/8" later model (after 2000) trans. Fortunately I received the $1,000 core refund, usually they say the trans they receive are toast.

The rear bearing fails first, causing 6th synchro to not work, then they get progressively worse and 5th synchro fails. Gear noises followed. I tow a 10,000 race trailer, Trans did not like load and high torque of engine options.



New trans works like a dream. Cost was $4400 + 450 for remove/replace. These are expensive transmissions and will become quite rare very quickly! Standard Transmission uses Amsoil Synchromesh fluid for their gearboxes.



I will install the Genos trans coolers that go on PTO, as trans temps while towing get to 210 degrees with Amsoil trans fluid which is too hot for my conscience.



I bought a 6 speed thinking I would avoid the failure cost of the automatic and discovered even higher repair cost. But now, with new SBC clutch, HO flywheel and gearbox, I should be all set.

 

[PAckley]

Also agree on 6th gear overdrive not able to handle all the torque while towing, so will also use 5th gear as recommended. Bought truck with 180,000 miles and thought I was nuts but no oil consumption, but no 6th gear synchro which was not a problem with double clutching. Standard Tranmission of FT Worth made me realize that the NV5600, especially early 1 1/4" spline were a problem, and the upgrade to 1 3/8's was smart. They feel these trannies will become extremely rare soon, so take care of what you got.

 

[PAckley]

Also, Standard Transmission recommends overfilling gearbox to help lubricate bearing in back of case which is the frequent weak link.

 

[Silver_Ram]

The Amsoil MTF is now out, & was replaced with Amsoil 75w90. I didn't add the limited slip differential additive yet. The FAST Coolers came off, the top of the passenger side cooler is so close to my 4" exhaust, I decided I could be getting heat soak.



I was told by the Trans Rebuilder not to overfill the trans, because it makes the trans fluid foam up.

 

[JasonCzerak]

hmmm, figured I'd update that thread with useful info and failed to do so.



I ended up with 1/2 bottle of limited slip friction modifier (napa stuff). I changed the fluid out to install a transmission temp gauge after shifting got a little worse. Like the fluid "broke down" as many of you may notice.



So I did the same again since the initial install of the lucas was good. This time around for some reason shifting wasn't right. Even in the warmer months.



Shortly there after I decided to try the friction modifier and things have been consistent and good.



I did flush the transmission with stock, cheap OEM transmission gear oil from pensoil for 100 miles prior to re-filling with amsoil, or make sure I got all that lucas crap out.



Winter driving has been a dream, It's never been so easy to row the gears when it's 0 degrees out! I do warm the transmission up a little by tossing the transfer case in N and row the gears quickly.



transmission temps are 100 degrees above ambient after 1 hour of highway driving over 60mph, or a few hours of stop and go city stuff. Unloaded. So in the winter time as you may figure, my transmission gauge doesn't move much

 

[steved]

So far, my best experience has been 2 quarts of Redline MT-90 and 7 quarts of Redline MTL... for summer driving only.



I tried 2 quarts of RP 85w190 and 7 quarts of Synchromax, but the shifting fell off within 8k miles... I have since went back to Redline.



I need to change out my current fill of MT-90/MTL for a straight run of MTL for winter use, but this fill has lasted the longest... 15k miles.



steved

 

[Gary - K7GLD]

I ended up with 1/2 bottle of limited slip friction modifier (napa stuff). I changed the fluid out to install a transmission temp gauge after shifting got a little worse. Like the fluid "broke down" as many of you may notice.

After reading the above, I tried adding the remains of my last differential lube change LS modifier - about 1 1/2 ounces - to my transmission which was recently filled with slightly over 6 quarts of the DC OEM lube.



Keep in mind my transmission was shifting what I consider well to start with - the typical SLIGHT "catch" on the 2-3 shift, and that only for the first half mile or so in freezing type temp's.



The added LS modifier has made a definite improvement in even my slight shift characteristics, and at some future point, will try adding another ounce or so of the modifier to see what happens - but so far, this is looking like an excellent tip...

 

[JasonCzerak]

After reading the above, I tried adding the remains of my last differential lube change LS modifier - about 1 1/2 ounces - to my transmission which was recently filled with slightly over 6 quarts of the DC OEM lube.



Keep in mind my transmission was shifting what I consider well to start with - the typical SLIGHT "catch" on the 2-3 shift, and that only for the first half mile or so in freezing type temp's.



The added LS modifier has made a definite improvement in even my slight shift characteristics, and at some future point, will try adding another ounce or so of the modifier to see what happens - but so far, this is looking like an excellent tip...

WOW, I know I didn't come up with the Limited Slip trick my self (read it from a few other posts). But it's nice to know even the old dogs learn new tricks from the young dogs

 

[Gary - K7GLD]

WOW, I know I didn't come up with the Limited Slip trick my self (read it from a few other posts). But it's nice to know even the old dogs learn new tricks from the young dogs

HAH!



Fact is, I have FAR more difficulty, criticism and conflicts dealing with the "old dogs" - you know - the guys who have been around forever, and sorta figure they already know everything worth knowing - "Don't confuse me with FACTS, my mind is already made up!" Just start challenging some of the old wives tales and "facts" that don't stand up under actual test, inspection and documentation - then stand back and watch the fur fly! :-laf



ANY "dog", old OR young, can always learn something new IF they have an open mind and are willing to learn - I had wondered about the modifier use in the 5600, but hadn't tried it because my transmission actually shifts quite well - not perfect perhaps - but pretty dern good! :-laf



Your comment was enough to motivate me to dump in the little bit of leftover modifier I had, and and happy to report improved transmission shifts. Strangely enough, the addition of the modifier SEEMS to actually make shifts better the COLDER it gets, just the opposite of the plain lube by itself.



Thanks for passing along the tip, regardless of who tried it first...

 

[FLynes]

I had my transmission rebuilt about 25,000 miles ago, in March. The dealer added a bottle of the LSD modifier, per my request. The transmission has shifted flawlessly, but I have noticed that lately shifting into 5th is sometimes rough. I notice it only when I'm quick-shifting up or when down-shifting at highway speed. I can only describe the symptom as a clunk noise. It doesn't always do it, though... . more like when I'm in a hurry. I've made a concerted effort to mash the clutch to the floor when I go to 5th now, and have had no problems. Any guesses as to the cause? I've been driving stick for 18 years, so I'm pretty sure it's not operator error, but you never know.

 

[JKinney]

I've made a concerted effort to mash the clutch to the floor when I go to 5th now, and have had no problems. Any guesses as to the cause? I've been driving stick for 18 years, so I'm pretty sure it's not operator error, but you never know. [/QUOTE]



Olie Poole reported and showed us a while back that a clutch slave was not pushing all the way. Pushing clean to the floor, is your slave failing?

 

[FLynes]

Could be. I would have figured that that would have been one of the things the dealer looked at, when they rebuilt the transmission.

 

[JasonCzerak]

HAH!

Fact is, I have FAR more difficulty, criticism and conflicts dealing with the "old dogs" - you know - the guys who have been around forever, and sorta figure they already know everything worth knowing - "Don't confuse me with FACTS, my mind is already made up!" Just start challenging some of the old wives tales and "facts" that don't stand up under actual test, inspection and documentation - then stand back and watch the fur fly! :-laf

ANY "dog", old OR young, can always learn something new IF they have an open mind and are willing to learn - I had wondered about the modifier use in the 5600, but hadn't tried it because my transmission actually shifts quite well - not perfect perhaps - but pretty dern good! :-laf

Your comment was enough to motivate me to dump in the little bit of leftover modifier I had, and and happy to report improved transmission shifts. Strangely enough, the addition of the modifier SEEMS to actually make shifts better the COLDER it gets, just the opposite of the plain lube by itself.

Thanks for passing along the tip, regardless of who tried it first...

Now here in lies a very good question. Was the addition of LSD additive really making things better? or is it all in (y)our head(s)?

I've always wondering if it's me, or the fluid making the difference in cases like this.

Once can kinda feel HP increase, but can one feel slight changes in shifting stiffness?

I think a double blind test is in order!

** Please note: LSD = limited slip differential ** Some of you may have noticed a possible correlation between LSD and "in your head"... Not that LSD.