What fluid should i use in the NV5600? Last time I put Mobil 1 and sometimes it hard to get in a gear when im sitting still reverse is real bad but it doesnt grind into it. What could it be?

 

I use the AMSOIL Syncromesh in my 2002 NV5600. Shifts like butter. But it came with the Pensoil Syncromesh which is readily available in most parts stores. Your choice..

 

Another vote for Amsoil MTF.

MikeyB

 

RP Synchromax works the best in mine - smoother shifting and less gear noise. Nothing will make rev work like the other gears cuz the rev synchro isn't the same. Mine works best if I hit rev before the countershaft completely stops. If it starts grinding going into rev, it's adios to the synchro - been there. Craig

 

I also have RP Synchromax. It really makes me wonder why they put synthetic in the diffs and the transfer and then dino in the transmission. The book says change the oils at such and such a mileage but only says check and top off for the tranny. I change them all.

 

I've run 3qts Valvoline 10W-30 syn motor oil + 2qts Valvoline 75w-90 syn gear oil in mine since I built and installed it with no problems - however, from your description, it sounds more like the pilot bearing in the crankshaft is failing, binding the input shaft - to check that out, push the pedal hard against the floor, try shifting into any gear, 1 thru 6, while stopped - if they're all difficult, it's the bearing

If the clutch pedal has less travel than when newer, it may be the master or slave cylinder is leaking - to check that out, pull the pedal up against the upper stop, noting the length of free travel - should be no more than 1" or so - otherwise, there's not enuff travel to completely disengage the clutch, which effect is worst at stop when the gears are not spinning

 

Why would you use synthetic 10w30 motor oil plus 75/90 gear oil when it requires a 5w30 fluid made for transmissions?

 

Hey guys,
From what I have read and after talking to some transmission builders I think you need to be pretty careful on what ya run. The info that I have gotten say that it's pretty easy to hurt the syncros with the wrong oil. For the NV5600 that we're building we are using the oil that Dodge recommends. I don't have the part numbers with me but it's in the owners manual.
Topper

 

It's all syn - the Texaco blend for oem use is nearly identical to 10W30 syn motor oil, but with more additive for the brass syncros - the syn 75W-90 has the additive, and is not really 75W thick - Texas winters are not as severe as those above the Mason-Dixon line, so the really thin-viscosity all temperature oil is not necessary - the 10W-30 is 10W\equiv at cool temps, offering 30W protection at elevated temps, which the NV5600 will never see - the syn 75W is not dino 75W viscosity, and is further diluted and thinned with the 10W motor oil - had the trans seemed to run hot, I would have switched from 3-2 blend to 4-1 blend - just an experiment with syn lubricants for a finiky transmission that are commonly available everywhere on a Sunday afternoon - two years running and no problem

FYI - the synchros in the early DEA with 1.250" shaft were problematical because the gears had no clearances for lubrication - the gears in the later DEE with 1.375" shafts were re-designed with slots and depressions specifically to correctly lube the synchros - problem solved.

One other thing - the NV5600 is a 6-speed ton-and-a-half\two-ton truck transmission, intended for hauling\towing, and works best when shifted like a big truck transmission - it is very unlike the wimpy 6-speed trans's in the Viper and the Corvette, which are intended for racing and such behind hi-rpm engines with fairly insignificant low-rpm torque - the differences in gear and shaft sizing is indicative of intended use, rpm or torque.

 

Just buy some Penzoil syncromesh, and be done with it. Don't waste time looking for some miracle synthetic.

 

What do you mean by "shifted like a big truck transmission?" Double-clutch it?

Thanks,
Nick

 

A big tranny takes time for the parts to mate through the sychros. A street car tranny will shift fast. Putting excess pressure on your shift lever before it mates wears synchros and detents etc faster.

You don't have to double clutch it, but you can if you want the exercize .

Cya

 

Not necessary, Nick, but like billie posted, the big gear train takes time to change speeds, even with big synchros, so the NV5600 doesn't respond well to quick shifting, particularly in cold weather - that's one of several reasons for the watery fluid spec'ed for lubricant - it's like sewing machine oil, compared to normal transmission lubes - another reason for the 'water' is coefficient of resistance - the big gears and shafts spin easier in the thin fluid than in thick fluid = better fuel economy - same with the thin stuff in your front and rear differentials and transfer case, and the thin syn motor oils - less resistance to rotation = greater efficiency

 

The fastest shifting manual I ever had was a Fuller Roadranger in a roadtruck. Fast as lightning with no clutch and never scratch a gear. I always heard that mixing oil weights was like mixing different size marbles. If you run your hand over them only the big ones carry the load. Craig

 

Aw, c'mon, now - you heard that from Forrest Gump, didn'tcha?