So what are your thoughts on oil? Are you going to stay with a Synchromesh fluid? How about different weights?

 

I was never a fan of penzoil .... after seeing the sludge the motor oil leaves behind.
I worked with a guy that restored a 1967 Ranchero and only used Penzoil and changed it regularly ... He pulled a valve cover off and it was disgusting inside ... I wont touch the product.

My NV3500 is in my chebby truck. I use ACDELCO oil in it.


Stuff is not cheap, $20 a quart from Amazon .... I have faith in the quality of it. I also do not do any towing ... a little Hot Rodding now and then ... my truck is a daily driver grocery getter.

I'm under the impression there is no other option for these transmissions ... they want syncromesh .... I could be wrong though.

 

Well when I rebuilt my transmission after the previously mentioned incident, I got rid of the oem synchros and installed carbon fiber synchros from synchrotech. At that point I'm not really bound to the whole synchromesh fluid requirement. I've thought about running synchrotech's own racing oil. Or just removing the internal bearing seals and running 75w90. Apparently the issue with gear oil like this is that it won't properly flow into the "sealed" bearings, hence why I would remove the seals. I realize this may affect shift quality but It's a 25 year old work truck. I'm not looking for sports car shift feeling, as long as it doesnt grind im ok with it. I just want an oil that won't make me rebuild my transmission next time I'm working it hard.

 

That is interesting....... To be honest, I never heard of a seal that would let a 10w30 oil in, but would hold 75w90 out....
Just my opinion, but I would think that if the bearing is sealed on both sides, then it has a "lifetime" lubricant in the bearing.
FWIW I know there are replacement axle bearings made that replace the factory bearings, which were oiled from the differential, but the replacement bearings are sealed with a lifetime lubricant.
Here is a link to one for a ford 8.8 https://www.rockauto.com/en/moreinfo...tUTlgvOQ%3D%3D

I wonder if that is what the replacement bearing you have is supposed to do?

 

The whole "oil not flowing into the bearings" portion is just what I read of Wikipedia. I'm not sure how accurate it is or where it came from. I am curious to try and verify it.

To your point on the bearings being fully sealed, every replacement bearing set that I've seen online, as well as the original ones (as far as I know) that I've pulled out of two NV3500's were all sealed on both sides. So I'm assuming that's the OEM design. Though I have removed the bearing seals on my old bearings when I pulled them out and there was definately no original grease still in there, it was all transmission oil.

I have seen re designed wheel bearings on axles like how you talk about. I'm pretty sure our trucks even have a new design for a sealed lifetime grease type wheel bearing. Though unfortunately I've never had the chance to pull one of those out and see how "lifetime" it is.

There's many gripes I have with the NV3500. I feel it was a solid design that was likely cut back by budget constraints. I don't like the bearings types used, the oil they specified, or the super small contact area of the shift collars on the dog teeth which makes it prone to having gears pop out under heavy use. I really want to make a video series about it and try out some ideas for improvements to those shortcomings. One day I'll be sure to post about it.

 

Well if the bearings are not perm. lubed, then it makes sense to remove the inner seal, especially if you are going with a thicker oil.
But its way above my paygrade to know.
Heck, I always heard these transmissions were very hard to rebuild.... took a bunch of speciality tools.
Would you mind telling me how to split the case so I could replace the front input bearing?

 

Rebuilding the transmission is not as difficult as most people make it out to sound. I've definately seen worse. It's a faily basic design with no shims required. Just for that I would say it falls into the easier half of the pile. Though I will say that simplicity is part of the reason for the sub-par reliability. A proper design would have shimmed taper roller bearings all around for silent reliable operation, and a center plate between first and reverse gears for shaft support where it's most needed.

as far as splitting the case, come in from the front inside the bellhousing pull your clutch fork and thrust bearing out and remove the front bearing retainer, 6 bolts.

next, you want to remove the bolt at the very top of the case just a couple inches forward of the shifter plate. This just secures an internal lockout to prevent shifting multiple gears at once.

the most painful part is removing the plug for the shift rail detent. It's located on the driver side at the very top of the case towards the front near where the bellhousing starts, the only reliable way to remove it is by center punch, drill, tap, and place a slide hammer on it. I have removed one with a flat head once, but that was miraculously easy. Most of these cases do not come open that easy and you end up drilling and tapping it anyways. Just save yourself the time and if you ever need to pull it again at least it will be ready to place a slide hammer on it again.

After that, there's I believe 11 bolts holding the two cases together, take those off and now you need to carefully wedge the case halves apart, i don't recommend using any hammers or mallets to smack the case halves directly. I've broken pieces of the cases off like that, the aluminum used is sub-par and fairly brittle, what i do recommend is coming in with a sharp scribe, pick, whatever you call it or a very fine punch and tapping the case halves right where the split is. Make a couple dimples on the mating surface very close to each other to where they basically all blend together, now you can place a flathead in that dented area and start tapping that in deeper, once you get the flathead in about 3-4mm the case will start to split, repeat the process 180° across for even lift. As far as what two areas to pick, i recommend the 7oclock and the 1oclock positions when viewed from the bellhousing looking towards the tail. That's because thats exactly where the two dowel pins are at which locate the two case halves together. And I know someone will say not to do this because it's a sealing surface. I'd like to point out the sealing surface is half an inch thick, that's almost 13mm. Ruining 3-4mm of that surface won't affect sealing capacity. I've taken my transmission apart 3 times, soon to be 4, and I've never once had it leak. This process will take time, be patient.

Once you've got the case to begin cracking open. Place the transmission with the bellhousing facing the sky, now you can bring in the pry bars to work the dowels all the way out. The front case lifts straight up and out, all the gears, shifter collars, and literally everything will stay with the rear case.

make sure to keep the rear case in that vertical orientation the whole time the front case is removed. Tilting it over places alot of cantilever stress on the rear bearings for both the output shaft and the countershaft, and can damage the bearings if youre rough with it, or can just cause them to come unseated from the case, and then you'll really be sorry.

And your front input bearing is ready to be replaced. Just need a slide hammer, or press or maybe just a mallet with a punch. They really vary alot on how tight they are. Best of luck to you!