FS5W71C knocking noise

[JarredH]

So, I was going to drive my truck 700 miles to Coronado because Navy things. I did some maintenance the truck needed before I left for boot camp and my first set of school. Plugs, cap and rotor, oil and filter. I decided since I don't know how long the transmission has been running the oil in it, I would do that too. Drained it, and that's when the horror show began. I was expecting the shavings on the magnet because that's just what happens. I was not expecting all of the gear oil to be a bright silver color. The transmission made a gear whine since I got it if the engine was running and clutch engaged, no matter the gear. Didn't have shifting problems at all. I figured with 248K miles on it, it's alright to have some whine.

Then I filled it with Valvoline gear oil. The old dude at Autozone assured me it was okay for GL4 synchronized manuals and wouldn't eat the brass when I asked him. I was still hesitant, but decided to listen to him. The was probably mistake number 1. Mistake number two, transmission only took 3 quarts. I saw the service bulletin, but it didn't apply to my transmission, so I though it was fine. Apparently not.

I made my drive fine without incident. I put another 600 miles on it since that drive a few weeks ago. Now, the transmission makes a nasty clunking sound when the clutch is engaged, idle or in gear driving. The whine is louder, but is nonexistent as far as I can hear in fourth. Still feels fine, 1-5 and Reverse work and don't feel odd at any point. The clunking going away with the clutch in makes me thing countershaft, but I'm no transmission expert. I'd like to keep this truck for as long as possible, but I only need it for another two months or so before it sits while I'm stationed overseas for the next few years. I have no place to work on it, so if it can't be done in a parking space, then I can't do it. I don't NEED to drive the truck, but it saves a few miles walk every day.

What do y'all think it could be? Did I kill a bearing? I'm okay with the whine for now, as it will be rebuilt fully when I get back home, but I need it driving again soon. If someone is in the San Diego area and has a spare transmission I could buy, that would be good too, but I'd have to use your driveway to change it out.

I'm going to pour some more oil in it through the shifter tonight or tomorrow morning before class to try and help it along, but the damage is done.

Thanks,
Jarred H.

[Desert Rat]

Valvoline is GL5 and has additives that eat the soft metals. In your case there probably wasn't a lot left of the sychros as it is.

4th is direct drive an is usually the quiet gear. 248k is borrowed time on one of these manual transmissions. get that GL5 out of there and fill her up with Redline MT90 or similar and save what you have left. With a little luck after a few hundred miles it'll quiet down with the proper lubricant.

[JarredH]

Ya think so? It's knocking pretty good in there. I also noticed today the truck kinda shakes when starting off, as if I'm not giving it enough gas, but that's not the reason. It's odd. Sorta made me think a clutch issue. I was told it was changed by the last owner, but no paperwork means it never happened. Wouldn't make sense for it to be related to transmission speed though. Other than that quirk, and feeling the clank through the shifter, nothing else has changed from when I owned it, besides a slightly louder whine, but it's gotten quieter when I added about a quart.

I mean, I can live without synchros helping me, but I really don't know enough about transmissions to know if something bad will happen if those go away. It's 2AM right now, so I guess the truck will have to deal with another day of GL5. Definitely going to have to do that before I drive to Perris Friday. Poor girl is gonna hate that, but if I can get my stepdad's Miata running, then the truck is gonna be retired for the next few years.

Speaking of that drive, is 4th probably the best gear to run it in for now, or does it really matter? The rattle is, as far as I can hear and feel, completely gone when it's in 4th.

[Desert Rat]

shakes when starting out could be clutch chatter.

[JarredH]

What I was thinking. COuld that be the knocking I hear? Hard to tell where it's coming from, it's a noisy truck all around.

[JarredH]

I'm having a difficult time locating somewhere that carries Red Line in san Diego. It seems Autozone has Pennzoil Synchromesh stuff, and the description on the website says it's good for bronze, brass, and copper. I'm not having much luck finding cases of people saying it's okay for this specific transmission. I'd assume it'd be fine if it's safe for the metals, and the right viscosity. Have any knowledge you can input there? There's also talk of the Synchromax Royal Purple, but I found one post saying it's too thin.

Here's a shot of what came out. Probably not much left of the synchro teeth as it was, they kinda worked. It hasn't been long since the GL-5 has been in, couldn't have gotten much worse.

[nalz]

In the last three years, I have rebuilt three FS5W71C variants, and all three had that "gray metallic paint" look to their gear lube. Game over, i'm afraid. The "graying" is caused by bearings wearing themselves down and shedding all that debris into the gear lube. My experience was similar, first was loud, and each successive gear was a little quieter, but fourth was nearly silent. On all transmissions, it was the large bearings up front, on the stubby main shaft, and the counter shaft, that came apart. I bought a rebuild kit and replaced all the ball bearings and synchronizer rings(btw, there are roller/needle bearings located between each gear and the mainshaft that did not come with this kit, when I called about this they said that these bearings always survive the gearbox grenading, so re-use is normal, and the rebuilt gearbox does have 122k miles on it now). The pilot bushing at the back of the crankshaft was worn down to FOIL!!!! normal pullers could not pull out the remains, but I found success with the "moistened bread" method. If you park the truck well before it forces you to call a tow truck, you will have less damage to other components in the transmission. It is absolutely possible to only "re-bearing and re-synchro" a gearbox and get another 150k, or even 250k miles out of it.