Shifting Issue

[RobertISaar]

perhaps try holding 3rd longer before shifting into 4th, see if elevated RPM there also causes it to happen in higher gears?

I would think if the hydraulic system were acting up, all gears would be effected equally.

what happens if you double clutch?

[Xnke]

Congratulations. You've found that annoying difference in a light-duty transmission and a medium-duty transmission. The larger gears (both in diameter and mass) mean the synchro's job is MUCH harder, and it takes a finite amount of time and friction to spin up/slow down those big gears. There are ways around it though-and it will "wear in" and get better with time.

Basically the friction surfaces on the synchronizer cones doesn't have enough contact area with the friction surfaces on the gears themselves. These two friction surfaces are essentially a wet clutch-and just like clutches, they need time to "mate" together.

The situation is worsened by loose tolerances on the synchro stack-most shops do not measure the synchronizer engagement distance to make sure the friction cones are properly mating up prior to the selector collar engaging the gear. They just rely on the parts suppliers to send them synchro rings that are "close enough" and normally they're a little too small-so they take a long time to "wear in" but they are rarely oversize enough to allow a newly rebuilt transmission to grind going into gear.

10-15 thousand miles and an oil change at the 7500 mile mark will help considerably. I see this in NV3500's, NV4500's, T56's and TKO's in Ford/Chevy/Mopar, FS5R30A and FS5R60A transmissions in Nissans, and some of the older heavy-duty Ford transmissions.

[Ace17]

RobertISaar
Hm, I haven't tried double clutching yet, I'll have to try that when I get back into town.

Xnke
I was actually thinking that it might need time to break in a little, but I wasn't sure. I heard from a few people that the syncros need to break in, but I've heard from many others that rebuilt transmissions shouldn't need to "break in". When you install them, they should just work. And that any driving done on a transmission that seems faulty could cause even more harm to the internals.

When I removed it last summer and the mechanic opened it up and looked at it, he said all of the synchros were new. I really hope the synchros just need to break in, because otherwise, this almost seems like a insolvable mystery.

[buddrow]

What Xnke says is true. Blocker rings are similar to brake pads, they will create a wear pattern once "broken" in.