Lunyfringe

I've bought a 'spare' nv4500, that needs 3rd gear syncros... I've started tearing it down, and honestly that's the only thing I can find wrong with it- came from a 2001 Dodge 2500 with a V10 (same part# as a Diesel) supposed to be around 80k miles, was taken out because 3rd gear syncros were bad (scratches going into 3rd)

it has the updated 5th gear nut- I don't tow more than 10k Lbs, and when I do tow, I'm never in 5th under 1700 rpms...

my question is, should I replace seals & bearings, even if they appear like new? it seems like all I'd need to replace is just the 3rd gear syncro (I know where I can order just the 3-4 syncros, for $19), and put it in... but I have to get the special tools to remove the mainshaft, regardless...

this is a spare- I have the same issue with my current transmission (I don't know why people are so hard on 3rd gear).. I plan on fixing the transmission currently in the truck after it's out as time permits, so I have a good spare again...

will put a filter kit, and put new fluid in it of course- and upgrade the clutch & pilot bearing at the same time.. but is it worth replacing what seem to be perfectly good bearings, just "while it's out", and then having to worry if I shimmed it correctly, to get the endplay & preload right?
I'm getting lilke 2-2.5 thousands endplay on the mainshaft and countershaft with these bearings...

thanks in advance,

p.s. this 12v IS modified- just plate & AFC work- but since it started as a 215hp model, I'm think I'm over 700 Ft/Lbs already- since the stock clutch WON'T hold it- I even backed off the plate, and it still won't hold..

Gary

gmctd

If the bearings you remove show no indication of metallic particles in the races or roller surfaces, then just replace the seals - but, if the synchro is chewed, you'll likely find the particles in the bearings, particularly the countershaft bearings.

You'll know for sure when you tear into it - but replace both seals either way.

fiveology

I agree, if a synchro is chewed up the material had to go somewhere, and it likely went through some bearings after it got into the fluid.

Common

Define "scratches"

If I don't give enough clutch to mine it will grind... is that OK?

Scramblinman

If I was pulling the mainshaft, I would replace it with a fully splined one and a matching new 5th gear regardless of it having been previously "fixed" or "updated".

Lunyfringe

I wouldn't describe the 3rd gear syncro as "chewed", the kevlar is worn out- but there's no metal contact... the only sign of anything spread around the transmission is fine black powder that appears to be worn syncro material (kevlar).. there is a small amound of fine metal powder in the bottom of the case, what I would consider normal (probably about a cubic centimeter at the most?)

the mainshaft upgrade isn't a bad idea- Quad4x4's website says they've seen failures of the fully splined mainshaft- anybody agree, or is that maybe guys towing 25K plus? I don't use my truck for my job, and I'll have a spare transmission, I don't mind a couple days downtime, just so long as it's not breaking down alot..

Thanks,

gunracer1

i say just a new set of seals and a syncro. why waste money.