Rattletrap1

Been awhile. IIR you take the side PTO cover off to drain. Correct? Or was it just a bolt for the side cover?

How about fill? I only see an apparent plug, not very high up, with a large but shallow female hex. Is that the fill hole? What's the hex size? 5/8 is sloppy. Special or fabbed tool using bolt head?

JohnnyH

I drain through the bottom PTO bolt, although you can also remove the entire cover if you want to have a better look at things and clean out the bottom. I did that the first or second time, but not since. The plug you are talking about is the fill. I used a bolt with a few nuts jammed together, but don't recall the size. Fill until it runs out, and then some if you can. I try to drive the left side of the truck on some blocks to get a little more in. Hope this helps.

Rattletrap1

Thanks. Went through the archive and found simialr/same info and that Autozone had the tool. Came in a 3-pack with a couple other sizes, but for $13 I wasn't going to complain. I'll likely over-fill a bit via the top bolt hole, but wanted the plug out for a reference. Fluid looks very clean so I'm not gonna worry about taking the cover off.

I had the trans rebuilt (exchange) 30K ago. They filled with Amsoil and I've never been happy with the way it shifted. Hopefully the MTL improves that. I'm tired of fighting with it.

KATOOM

The 5600 needs to be overfilled a qt or two for ample bearing lubrication. And make sure the fluid you use is the proper weight too. 30k seems way to low of miles to rebuild this tranny. There is some confusion out there regarding the correct weight as some are trying to use 75-90 and this tranny needs the OEM 5-30 weight. Here's the spec sheet on the OEM fluid.

Rattletrap1

MTL is the right oil. Texaco doesn't even market MTX and haven't for years. Pennzoil Synchromesh is the direct replacement. Viscocity is only one part of the requirement but the MTL (75w80) satisfies the viscosity requirement of 5w30 engine oil.

Mixed reviews about overfill. I haven't kept up with the latest, but recall some folks with gauges saw temps increase with overfill. The Getrags were well known for needing overfill and even Dodge spec'd it (later?). Nevertheless, I overfilled a bit.

SIXSLUG

Fill hole is a 17mm hex IIRC.

1 qt overfill is sufficient on early castings that do not have the pass thru hole at the rear. You will only know this if you have it apart....
The later ones had a square oval hole, rebuilds usually get a 1/2"-3/4" hole drilled out.

Use the correct lube or you will suffer. I used Pennzoil Syncro.

If the drain oil is full of golden flakes your blocker rings are wearing out. Usually do to trying to shift too fast and not letting things line up.

Rebuilding this model is spendy, around $1800 IIRC

totalloser

Extra quart is a must not only for the ports, but to aid in adequate cooling of mainshaft/IP shaft bearings. Use top pto bolt, or shift tower to fill.

This transmission gets HOT. Hot enough that when towing heavy, non synthetic will carbonize and gum the synchro assemblies up causing lasting, but diminishing problems. Full synthetic oil ONLY. I ran the factory stuff for a while (GM since the dealer couldn't figure it out) but run royal purple now. Lots of folks run amsoil or redline- you will notice surprisingly smoother shifting. The reason it gets so hot, has a lot to do with the iron case. Iron is a pretty terrible conductor.

BTW wearing out blocking rings usually has more to do with morons who shift without the clutch thinking it's like a big rig non-sync transmission, which it is NOT.

If it's shifting poorly with amsoil, It might have a dragging clutch. The OE style 13" clutch uses a solid hub with a riveted sheetmetal plate extending out that supports the friction material. I twice wrinkled the backing making the clutch drag before going to a valair HD disc that extends to the friction eliminating this "issue".

But you will NEVER make this transmission shift particularly smooth, the components are just too heavy for smooth shifting from the transmission. It will shift smoother and faster with practice though. You eventually develop a feel for it.

KATOOM

Just curious totalloser but have you ever measured the temps on this tranny? I ask because after installing a temp gauge on my 4500 I found the running temps under certain conditions interesting. I ended up installing Fastcoolers and an exhaust blanket (not wrap) on the section right next to the tranny and my temps are now well under control while towing a 14k 5th wheel in the summer.

SIXSLUG

Mine shifts like a dream with 13K lbs of boat behind it.

Forcing the shifts can and do grind the noses off the blocker rings...

Rattletrap1

Ebay vendor sells 1 & 2.5 gallon containers of Mopar NV3500/5600 fluid for ~$8.50/qt plus shipping.

Search NV5600 on Ebay.

Of course, I just got done putting in Redline MTL at twice the price, but still beats dealership prices.

SIXSLUG

My experience with Redline MTL was it shifted easier, but not smoother. This may have been due to the PO using the wrong fluid. I found a rec't for a trans service rec'd at minutelube in oregon at 37K miles. This was in 04.
When I changed it out it was yellow and milky and smelled like gear lube. I put the plug back in and flushed it with diesel, drained it off and blew it out before running the Redline.
I got it with 53K on it and it got to where I couldn't get it in reverse without shutting it down on the flats.
The trans shop couldn't get it apart so I got a warrantied rebuilt one of the newer design, which was like the original.
The trans was 1850 and the total bill was around $4200, but that was with an SB clutch and hydraulics...
My trans guy said to run the stock stuff and I shouldn't have any further problems and at 137K, I haven't. My last change was with Pennzoil Synchro because the Texaco stuff was almost $30 a qt.

DIESELWRKS

193k since 80k been using Redline or Penz/Snych whatever was cheapest but mostly Redline. putting in 2 xtra bottles. my first change about 80k had brass flakes who knows it it was alot? nothing to compare it to. I ran the NV5600 PTO cover filter for almost 80K miles and just recently did not put it back in when i did last oil change since I didn't have a new filter.

I do at times experience some grinds or not so even lined up shifts. But that is to me the combo of having a grabby double disk, and shifting in higher RPM's. I think it will need a rebuild in future but hell if I can make it to 225k miles I'm happy with that.

SIXSLUG

Supposedly IF the fluid is changed correctly and IF the shifting isn't jammed the 5600 should easily see 225K miles.

My issue is I get impatient from 4 to 5 and get a little bump more often than not.

Also, I haven't accidentally hit R in a long, long time!

totalloser

Haven't bothered. I bought my truck with transmission problems- the synchros were sticking badly when warm, and the best determination was that the PO had gotten it hot enough to literally cook the oil into carbon. It eventually worked itself out with some redneckery I'd rather not share (parts were not available at the time due to GM/NV/Chrysler drama) but since then I haul pretty heavy now and then with no problems with full synthetic.

My suspicion is that the synchronizer struts were sticking in carbon in the hub in the engaged position preventing the collar from retracting to disengage the gear, but parts unobtanium followed fixitselfium have limited my knowledge of the issue.

I base the advise on many years ago discussions, and rebuilder recommendations. The extra oil helps keep the mainshaft IP/OP bearings *cool* which was linked to premature failures, and obviously synthetic holds up better- but it also shifts A LOT better. I have heard that Redline is the best, but like I have said before, I am happy with the performance of royal purple. The only reason I wound up running it was that I had the trans back in with a new Valair clutch and realized I didn't have oil right then and there. Napa had the stuff in stock, and once in, I was happy with the smoother shifting.

SIXSLUG

My concern was that no rebuild was available.

Rumors! My trans guy had one the following day...

He also said an interesting thing, the aftermarket oil's special ingredient was colored dye. I have run "stock" juice in mine, either the Texaco or Pennzoil brand, with no issues...

The Redline helped mine at first, but then the damage was too far done to help.