Grinding going into 4th gear

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rrich1
Posts: 52
Joined: December 29th, 2018, 4:02 am
Model Year: 1931

Grinding going into 4th gear

Post by rrich1 » April 24th, 2020, 1:46 am

Hi,

I have not been able to drive the AA a ton since I got it due to different reasons but something I have noticed is that 9/10 times I grind 4th gear. I double clutch and try to adjust for speed like the other gears and have no issues. 4th gear though will grind. I have replaced the transmission oil and now would like help as to what to look at next. thanks.

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Chris Haynes
Posts: 2117
Joined: September 7th, 2003, 5:18 pm
Body Type: 82A
Model Year: 1930
Location: North Hills, CA/ Pine Grove, CA

Re: Grinding going into 4th gear

Post by Chris Haynes » April 25th, 2020, 9:52 am

I actually shift gears without using the clutch. It is a matter of timing. Slipping out of one gear and gently moving towards the next and feeling when it is ready to mesh. If it grinds you are not allowing the gear speeds to be compatible.

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tiredtruckrestorer
Posts: 320
Joined: April 20th, 2003, 7:09 pm
Model Year: 1931
Location: Orwigsburg, PA

Re: Grinding going into 4th gear

Post by tiredtruckrestorer » April 27th, 2020, 7:38 pm

When your shifting into high gear, you're are actually connecting the front of the mainshaft to the rear of the input shaft. Often I found that the front of the mainshaft is worn where the bearing rides on it and messes up the alignment between it and the input shaft. Other factors can also mess up this alignment such as not dial indicating the flywheel housing when installing it to the engine and/or not using the correct amount of brass shims on the top two bolts of it. Sometimes the housing itself has to be ground to true it up.

What I'd do is pull the top cover of the transmission off and check how the fourth-speed gear slides front into the rear of the input shaft. If it doesn't slide into it without moving it up and down a lot, you know there is wear in the connection. Sometimes I found that the special washer that fits on the mainshaft was never put in there to keep the bearing from moving back and forth on it.

I don't know what gear oil you put in the trans, but Ford used a 600 W . This is equivalent to a straight 140 gear oil, not the 80-90 or 85W140 that most auto parts stores sell. Today you may have to find a Industrial oil supplier to find this. I'm not sure what the Model A parts suppliers are actually selling as their 600W gear oil, but I'd don't think it is a straight 140 gear oil. The heavier oil will help slow the gears down to make easier shifting too

Keith.

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