CINDYLMILLER

Wont go into 5th sometimes, but if i grind a bit in reverse it goes strait up and in 5th, usually.
I know that has to be bad but so is no 5th at 70 or so, right?
1999 3.8L

stevieturbo

You're actually trying to engage reverse at 70mph before trying 5th ?

It's a miracle the whole thing isnt fucked.

But really, there are many things that could be the cause of the problem, and if it is just a single gear....all of those are going to be inside the box.

CINDYLMILLER

No , of course i try 5th first , but someone else driving it discovered that by just slightly down towards reverse, not actually trying to completely go into reverse, and then back up into 5th, that it usually goes into 5th. But that doesn't always work either. All other gears are fine. And has a new clutch.

Firebrian

You could try double de-clutching which often makes shifts a little smoother/easier. That could be simple fix for the few times you need to get up into 5th gear each day.

CINDYLMILLER

Hey thank you so much. It works great!!
I really appreciate it!

Firebrian

Since 4th to 5th is now a noted weak point in your transmission I'd minimize how often you get up into 5th gear...ideally for extended runs. But, the double clutching with revs matched will minimize the work that the synchro's have to do to match rpms. Since double clutching takes a bit longer to do, the RPM has a chance to drop under the actual shift point...which makes the synchro's work harder to spin back up to speed. I would calculate what ideal speed/rpm on the highway that shift should be done. And try to stick to it. I'd also ensure the amount of force applied to the shift lever is minimized to prevent any unnecessary force applied to the shift fork. No reason to slam it into 5th. Just apply pressure evenly to it until it wants to slide into place indicating synchro/hub/gear speeds are matched up.

You might also review the trans fluid you are using. The wrong fluid (too slippery-like many of synthetics, wrong add package, or wrong viscosity) can make your synchros not work as well. All of that leading to more wear, and therefore earlier failure. Your fluid could also be quite aged or sheared after 10K or more miles - especially if using conventional ATFs, which can shear down 30-40% in 10K miles. If it were my Tremec T5 transmission I'd only want to be using a conventional ATF such as the GM trans fluid 88861800 (GM/AC Delco 10-4033 at $6-8/qt) which is a slighted beefed up Dex 3 ATF with more friction modifiers and anti-wear additives than the budget priced conventionals. There's nothing wrong with using a Pennzoil, Mobil, Valvoline, Castrol conventional Dex 3 at $4/qt.

I've read enough blogs on what people use and the recommended synthetic ATF's don't work for everyone, even the Tremec recommended Mobil 1 ATF (that list includes Amsoil ATFs, Redline D4, RP Synchromax). I'm assuming that since the V8 T56's came with paper composite friction rings in 1999, then so did the T5's. These earlier style (non-carbon) rings are fussier with fluids than the ones from 2001 and later. Another reason to stay with conventional ATF's.

If your trans has a lot of miles on it, you have to expect for things to wear out. Synchro's are often the first thing to go. And when or if downshifting out of 5th gear, doing it at a lower rpm will make it easier on the synchros. And in this case, double-clutching with a rev match is more important than during a 4th to 5th, for synchros and clutch wear. Wear is wear no matter on the up shift or down shift. The less wear you have, the longer those 5th gear synchro's will last....though typically it's the 2nd, 3rd, and 4th gear synchro's that tend to get abused.