Intermittent 1st gear grind

[datzenmike]

Perhaps wrong but as I understood it wasn't a shift but an intermittent grinding sound while driving in first.

 

Stuart720 Is while driving in first gear, or while shifting into first gear?????

[thisismatt]

Pulls hard to the right when happening would rule out transmission 100%.  Sounds more like axle or brake related.

[datzenmike]

How does it know to only do this in first gear??????

[thisismatt]

7 minutes ago, datzenmike said:

How does it know to only do this in first gear??????

 

Possibly torque related.  Maybe a spider gear is letting go in the diff?  

[Stoffregen Motorsports]

I thought he said the shifter pulled to the right.

[datzenmike]

He did and I think this was while it was in the 1st gear position. I suggester holding it firmly in first and he reported it was less grinding.

 

On 7/26/2023 at 1:40 PM, stuart720 said:

I see. So 100% driving it like a normal person would. Push the clutch in, shift to first, let clutch out, apply throttle, rpms hit 2000-3000, "rink"-"grind", let off throttle/ apply clutch/or power through, noise disappears. Not a problem in any other gear. And it's intermittent, It does not happen every time I'm in first. Roughly 1/10 times the noise is there

 

The pull to the right is something trying to seize I bet.

[stuart720]

Yes happens only IN gear, rolling down the road, 1st ONLY, around 2-3k on rpms. And it's still extremely random.

 

Pushing the shifter up and left helps, when it happens, some. I do not make this motion a habit tho.

 

New motor and clutch kit...

 

flywheel and tranny are the same ones I've been running for 12 years. 

 

Didn't touch he transmission other than to separate, install throw out, and marry to the new

 

Ideas on what you think is seizing?

 

I have a hard time making sense of any of it. If something was failing I would expect to gradually experience it more. Not just Tuesday afternoon after 50 miles pulling away from a stop sign. And that might be it for the week.

[datzenmike]

Did you say you have drained the oil? If you haven't do so. The  drain bung has a magnet. Look for filings and metal pieces.

[stuart720]

Yes I did, royal purple at first.

 

Swapped it for some sta-lube, thought maybe the synthetic had something to do with it.

 

There was a couple shaving and a gooey paste, but nothing id call excessive.( second fill was clean)

[datzenmike]

Sorry, too lazy to check back. I remember now. Well from the description something is rubbing something moving. If a grind, then something not smooth but gear like, and only randomly in first.

 

 

First gear on the mainshaft is the one on the far right. The first gear on the counter shaft that drives it is below it. The adapter plat to it's tight supports the mainshaft with a ball bearing. That little sheet metal thing sticking out of the adapter plate is called a 'gutter' and it catches oil splash and directs it into the tail shaft side of the adapter plate to improve circulation on that other side. Can't see it rubbing hard enough to fit the description.

[Stoffregen Motorsports]

Pushing up and left on the shifter while in first is going to move the shift fork ever so slightly. If this does in fact help, then ther has to be a problem inside the trans. Could be with the shift fork or shift rail, or the sleeve, hub or pawl springs inside the hub (that locate the synchro). There is a roll pin that holds the shift fork onto the shift rail and these have been known to break or walk out partway. If it starts to walk out of the fork, it could protrude into the gear, causing the noise. As an improvement, there are "dual" roll pins which have a small roll pin stuffed inside the outer pin. These are about twice as strong both in shear strength and in the tension that holds them into the fork.

 

I know you said you didn't have the trans apart, so maybe this is just coincidental timing.

[datzenmike]

 

On the 71B as least the roll pin isn't a problem.

[Stoffregen Motorsports]

How about on the other end of the rod? Is the first gear selector close to fifth gear?

[datzenmike]

Fifth gear shift rod is on the very bottom and fifth/reverse gear is in the tail behind the adapter plate. It's only that long to reach the reverse light switch.