Okay there seems to be some confusion on what exactly is the correct fluid for this tranny. I have researched and come across some that say any name brand 5w30 is what to use, others say dodge Synchromesh, and others say 75 90 gear lube. What is the correct fluid for this tranny really. Also anybody know what size that Allen plug for draining and filling the tranny is? I don't have one that fits it and will have to buy one

 

Funny you mention that. I was looking on line at the transmission you purchased and it appears they say any 10w30. I would call them and ask. The NV3500 is supposed to use synromesh 10w30 which is not motor oil. Pennzoil and several others make it.
Or look in your owners manual and see what they show. But I believe you will shorten the life if you do not use the proper fluid.

The drain plug, is a 17mm. VW uses the same size. I purchased a short one on ebay, that I then can use in a socket. $10.00

 

I checked the website and it says 5w30 of any name brand and then I called them and the guy I talked to said that they use 5w30 but to be honest the residue leftover fluid in it from them running it on a dyno looks almost like ATF.
I wanna make sure I run the right stuff so it lasts a long time.

And okay thanks for clearing that up I could tel it was a rather large Allen bit.

 

This is from Allpar.com's section on the NV3500:

I use Pennzoil Synchromesh.

 

Thanks! I may try the Royal purple bc im not a fan of any Pennzoil stuff personally. And have you had good luck with that fluid?

 

I understand. So far, no problem with the Synchromesh fluid, but I may try something different in the future. My trans is quiet, smooth, and shifts pretty well, so I can't really complain, but if I had to come up with minor gripes, it would be that the throw is maybe a bit long and the movement is stiffer than I like. I'm used to a Neon RT as my daily driver though, and it has a very light, quick shift which has spoiled me.

If changing to a different fluid could give me a lighter feeling shift, I'd be interested in trying it.

 

Oh I know the feeling I have a little Ford zx2 for a daily and it's the same way. Also check out my other two new posts on the cross member and the 3500 update I need some input.

 

I have used Pennzoil Synchromesh for the last 300k miles with no issues. I change the oil when shifting feels a bit notchy usually every 40k miles. I have a 4k lb trailer hooked to this truck since day 1 and do firewood deliveries only with it so if this fluid wasn't good I would have had to buy a new trans by now. If I had to do it all over again, I'd just change the fluid sooner at 30k since it's easy and cheap. The Allen bolt is a 17mm Allen head socket and I use about 5ft of 3/8 inch inner diameter clear tubing routed up into passenger side of engine and other end stuffed in trans with a pan under and then I can put the tubing on the oil bottle and squeeze in the first qt comfortably from the engine compartment and then I do about another 1/4 qt then go see if it's overfilling below. Keep going until it comes out the fill hole and then put the Allen plug back in and done. I usually buy 3qts and that's enough for 2 changes. I have heard the amsoil is a smoother shift but haven't tried it. Any fluid you use must be for Synchromesh as these are bronze synchros and they will dissolve or etch with other oils. Pennzoil Synchromesh is cheap and easy just use that

 

syncromesh stinks .... practically burns the nostrils. It must be good. I use it and no complaints, other then the smell.

 

I have used penzoil synchromesh exclusively since I got my truck 30k miles ago. But I am definately not a fan, I use it because it's the only MTF that my local parts stores carry in person. That being said, last year I burned up my input shaft gear and the meshing gear on my countershaft which both chipped pieces that caused damage to all my other gears and left my transmission whinning like a straight cut racing trans. I 100% blame it on the oil, the transmission was serviced up the fill port. I was being pretty aggressive on the gas while climbing up to 4k feet just outside of Yuma on my way to San Diego. It was definately a hot day likely around 90F and I had been running the truck at 75mph for hours as I was on a road trip. I understand the transmission was likely heat soaked, but my engine is stock and I was in 3rd gear around 3500 rpm with not more than 500lbs of stuff in the bed. I'm assuming my oil thinned out and stopped lubricating from the excess heat. In my mind any decent oil should be able to handle stock engine power on a 90F day without completely breaking down.

I have since learned from my lesson and installed a simple temp guage through a hole I drilled in the fill plug. And while driving under similar conditions I have seen oil temp as high as 210F after hours of 5th gear driving at 75mph on a hot day on flat land. Dropping to 4th gear drastically drops the temp (as you might imagine) after 5-10 minutes down to 190F. The coloration on the gear teeth suggest that they got up to around 530F that day. I'm sure the oil at that point was basically useless.

my point in all this is to say that I don't think penzoil synchromesh is up to the task if you plan to WORK your truck or tow heavy at low speeds. Ironically enough if you tow heavy on the freeway you likely do it in 4th gear which means the transmission is basically generating no heat. I will running various oils and putting my truck through the paces to get real life temp indications and will post my findings. All too often people talk about different oils based on how they "feel" it works but I want to get some numbers down. And a transmission cooler is definately in the works. I included pictures of my burned up gears below.