Manual transmission scraping noise / grinding sound

[I3lackRose]

It’s really interesting that everyone that has posted to the sheet that their transmission was replaced had the noise come back. So, either all the replacements are defective as well, or those particular broncos have something wrong that damages the transmission.

That has been speculated too as it possibly being a outside influence causing internal damages. Not a single replacement trans or TSB have reported solving the noise more than a week or 2 for the most part.

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[I3lackRose]

Mine was destined for dealer tonight anyhow but

In addition to the noise.....I found the spot it grinds gears. It's Halfway into 2 and you can feel as though something is just partially in the way if you move to the left side a bit it stops. Like a synchro not sliding side to side to engage/disengage would anyone think? Now the clutch was to the floor whole time and I was able repeat that grind by slowly shifting in and out to 2nd with adding small amount of side.play. However the other times it was already in 2nd when in randomly began grinding gears so must be enough slop somewhere it's able to interfere and catch while clutches in? Not sure if that info helps anyone mechanically inclined.

I also notice that if I'm moving the only positions while clutches in that I hear the scraping is if it's in one two or three..... When in four five six and N even if I'm rolling slow and I'm switching in and out of those the noise is gone quick but once I switch into one two or three crawl or reverse you hear the scraping does that possibly mean all of those lower gears are being affected while 456 are fine

 

[Emily]

I've been watching and reading this thread since day one. I'm on the spread sheet.
Today it's around 70 here in south central PA. Started my truck this morning 40 or so.
Drove to work heard the noise. I drive home for lunch every day. Now it's 1PM and 70 degrees. Heard the noise at start up. Drove thru town and got home. No more noise. Eat my lunch, 30 min later, started my truck. No noise in any situation. Clutch in, clutch out, in gear, moving slowly, no noise. Drove back to work, no noise.

Just a thought, but what if it's not completely a weather temperature issue but a vehicle temperature issue.

 

[Tricky Dick]

Just a thought, but what if it's not completely a weather temperature issue but a vehicle temperature issue.

Mine does often go away when the vehicle warms up. But temperature doesn't seem to be the issue, just what reveals the issue. Strangely, this morning it was 6F at first start up and it was silent.

 

[I3lackRose]

I've been watching and reading this thread since day one. I'm on the spread sheet.
Today it's around 70 here in south central PA. Started my truck this morning 40 or so.
Drove to work heard the noise. I drive home for lunch every day. Now it's 1PM and 70 degrees. Heard the noise at start up. Drove thru town and got home. No more noise. Eat my lunch, 30 min later, started my truck. No noise in any situation. Clutch in, clutch out, in gear, moving slowly, no noise. Drove back to work, no noise.

Just a thought, but what if it's not completely a weather temperature issue but a vehicle temperature issue.

I would agree with you. Mine is there most the time. The warm up idle it's always there regardless of temp it seems. If the vehicle is a little warmer I only hear it at slow speeds but goes away during regular idle. But move slow in low gears and it scraps

 

[gtabert]

I would agree with you. Mine is there most the time. The warm up idle it's always there regardless of temp it seems. If the vehicle is a little warmer I only hear it at slow speeds but goes away during regular idle. But move slow in low gears and it scraps

Thinking out loud, this sure sounds like an issue with the Syncro Assembly. Relating this manual with the Ford Toploader, the terminology I'm using here is from that transmission which I'm familiar with - Starting with the thrust washer(s) which may to too tight or too loose. Perhaps a clearance between the syncro and it related parts within the syncro assembly, at each end are bronze blocker rings. Or, what is called Syncro Keys, then perhaps any "C" springs or a snap ring, or a combination of any of these parts. Any of which should rear their ugly head upon disassembly. Their are simply too many common threads between everyone's problems not to be evident.

 

[smiths65]

Mine has undergone the TSB surgery, accordingly to the service technician...has come out quiet. Mind you, I have not picked it up, nor has it been driven much other than a few miles to verify ease of shift & noise verification...still have the hardtop to replace (waiting on the sound deadening to be installed, cured and windows/hatch re-seated). There were other issues internally that were addressed, in addition to the 5th/6th synchros. I will get all the details and post the technician findings once it is fully ready-to-go.

 

[Tricky Dick]

There were other issues internally that were addressed,

Very interested in this!

 

[smiths65]

Very interested in this!

I did post that pic earlier of that gear cog...not fully sure which one it was.
But, like I posted earlier...hopeful that the write-up will be detailed & have forthcoming info for all

 

[Bmadda]

Mine was destined for dealer tonight anyhow but

In addition to the noise.....I found the spot it grinds gears. It's Halfway into 2 and you can feel as though something is just partially in the way if you move to the left side a bit it stops. Like a synchro not sliding side to side to engage/disengage would anyone think? Now the clutch was to the floor whole time and I was able repeat that grind by slowly shifting in and out to 2nd with adding small amount of side.play. However the other times it was already in 2nd when in randomly began grinding gears so must be enough slop somewhere it's able to interfere and catch while clutches in? Not sure if that info helps anyone mechanically inclined.

I also notice that if I'm moving the only positions while clutches in that I hear the scraping is if it's in one two or three..... When in four five six and N even if I'm rolling slow and I'm switching in and out of those the noise is gone quick but once I switch into one two or three crawl or reverse you hear the scraping does that possibly mean all of those lower gears are being affected while 456 are fine

"halfway into 2nd" is not a proper way to shift. Synchros only move in one direction. The shift sleeve contacts the blocking ring 1st. The purpose of the blocking ring is to act as a brake to match the rotating speed of the 2 components. Once speed is close enough, additional pressure can push the sleeve onto the gear (the "hard part"). If you "limp wrist" your shifter so that you only catch the blocking ring, but not completely lock the sleeve to the gear, then yes it's gonna grind...don't do that. If you are 100% sure that it's all the way in gear, and it has a tendency to "pop out" of gear and grind, then the issue could be internal, or cable adjustment. There are detents that hold the fork in place once fully engaged. They are generally just a ball w/a spring behind it that catches a groove in the rail that the fork is pinned to. Sometimes the spring breaks...but usually that's after LOTS of miles. They are easy to hear if you listen to the trans underneath (with the vehicle shut off and parking brake set), Have somebody shift all the gears while you listen. Should be a nice solid click sound for each. W/the cables off the trans, you can feel them moving the levers by hand (this is how I check after re-assembly of a manual trans). Here's a pic of what the lever positions are:

 

[Classic28]

73 degrees outside at startup this afternoon, no noise. First time I haven’t heard it in months lol.

 

[amazingjason]

The "does your 7MT make noise" poll here was around 70% yes. Not even the 2.7 had that kind of rate. Since many of ours are very quiet or completely silent when temps are warm, or took several thousand miles to show, it would not surprise me if every 7MT has or will have this problem.

Could people change their vote if the noise appeared later?

Jason

 

[I3lackRose]

"halfway into 2nd" is not a proper way to shift. Synchros only move in one direction. The shift sleeve contacts the blocking ring 1st. The purpose of the blocking ring is to act as a brake to match the rotating speed of the 2 components. Once speed is close enough, additional pressure can push the sleeve onto the gear (the "hard part"). If you "limp wrist" your shifter so that you only catch the blocking ring, but not completely lock the sleeve to the gear, then yes it's gonna grind...don't do that. If you are 100% sure that it's all the way in gear, and it has a tendency to "pop out" of gear and grind, then the issue could be internal, or cable adjustment. There are detents that hold the fork in place once fully engaged. They are generally just a ball w/a spring behind it that catches a groove in the rail that the fork is pinned to. Sometimes the spring breaks...but usually that's after LOTS of miles. They are easy to hear if you listen to the trans underneath (with the vehicle shut off and parking brake set), Have somebody shift all the gears while you listen. Should be a nice solid click sound for each. W/the cables off the trans, you can feel them moving the levers by hand (this is how I check after re-assembly of a manual trans). Here's a pic of what the lever positions are:

Thanks for all that detail. Very good stuff. As far as the random 2 times it ground gears. It was in gear with clutch to floor. Didn't visually pop out or feel not in all the way when I did go to move it but it might just be sloppy enough it did and the stick just didn't move far. The other situation was it randomly high reved for 2 seconds when in 2 clutch to floor. I do feel second does not always feel the same grab in to gear that the rest do. I don't generally limp wrist my shift but with a bunch of playing shifting specifically In And out of 2 I was able to get it to grind.

 

[Tricky Dick]

Could people change their vote if the noise appeared later?

Jason

I did.

 

[bniknar]

Hey - since this forum is all about m/t, I wanted to distract everybody from the grinding woes by showing a simple mod to the shifter: replace the vinyl shift boot with a leather boot. See https://www.bronco6g.com/forum/threads/7mt-club.33588/page-9#post-1658330 for a chat.

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