Deegee

iTrader: (1)

Hi guys,

I just picked up an SC400 (1UZ) with a W58 5 speed conversion and I've noticed that when going from 5th gear to 4th on the highway, it grinds. Automatically I'm thinking this could be a synchro issue but I haven't had the car long enough to mess around with it.

It shifts great from 3rd -> 4th and so forwarth, and it only grinds when I'm downshifting to 4th, usually above 40MPH is when it grinds. If I slow down any less than 40MPH, and downshift from 5th - > 4th, I don't have any grinding.

I've been thinking about replacing the w58 all together, but I also thought if I could save a few bucks I could just go with a
Could there be any other reason besides bad synchros that this could cause this?

Thanks

LEXXIUM

iTrader: (1)

I'd love to help you, but i would check clutch master, lines and slave to make sure everything is working the way it should, before making that synchro call.
Make sure nothing is leaking from fittings to cause your clutch not to fully engage.
.p

Ali SC3

iTrader: (10)

may not be disengaging fully, would check that first. no one rebuilds a w58, its not worth it.
It can be done though check our marlin crawler they probably have a dozen w55's on the bench right now and they are practically the same thing.

KahnBB6

iTrader: (5)

It vaguely sounds like a synchro issue... but I agree that you should check the clutch system and hydraulic lines first to be sure. Something so severe as 4th not working about 40mph does sound like it though.

Marlin Crawler, Jack's Transmissions, Driftmotion and SpeedForSale all work on W58's but the cost of a rebuild is the same as with an R154, but with none of the added torque holding.

A rebuild to stock specs should be just fine for the W58 against a stock non-VVT 1UZ though aside I do believe there is a strengthened race-only (dog) PPG gearset finally available for the W series now... for the astronomical price of about $8,000.

OP, all other things being equal if you like the car enough as it was before the issue, a rebuild ought to only set you back about $550 ballpark in labor and parts. The removal and reinstallation would add a bit more labor if you have a shop take care of that.

Ali SC3

iTrader: (10)

another trans to consider is the z32 5 speed in there and call it a day, they have adapters for the 1uz now. crisp shifts similar to the w58 cause it also uses a remote shift setup (where the 350z inherited its beefiness and good shifting from), but it can hold similar power as a r154. they came on 300zx's both turbo and non turbo got the same transmission. usually under 500 bucks and none of the swap issues the 6 speed has and at a fraction of the price. you dont get the 6 speed, but you get a box you can beat on without needing much of a rebuild.
with stock v8 power though you could just find a cleaner w58 and throw that in there. if you have to rebuild find a r154 and have that done although some shops are reluctant to work on those anymore due to lack of parts availability.