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Old 06-01-2021, 08:00 AM   #1
Magoo2
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Default Downshifting problem

Other than operator error (which is a real possibility) what are the mechanical issues that would cause gear grinding while downshifting? Just got my 31 CCPU running. Whenever I come to a hill or turn that requires me to downshift I have to come to a complete stop and start off in first gear to prevent grinding of the gears. Iíve tried double clutching and accelerating while in neutral before trying to downshift to a lower gear but it just does not seem to work.
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Old 06-01-2021, 08:09 AM   #2
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Default Re: Downshifting problem

There are no synchronizers. Get someone to teach you how to double clutch. Search YouTube. Good luck.
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Old 06-01-2021, 08:33 AM   #3
Ray in La Mesa
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Default Re: Downshifting problem

It does take a bit of practice. You have to rev the engine a LOT more than you think you should to downshift.
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Old 06-01-2021, 10:01 AM   #4
rotorwrench
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Default Re: Downshifting problem

It's all about matching rpm between drive input (engine rpm) and output (rear axle & mainshaft rpm) on non-synchronized gears. It's best done by ear but it takes a lot of practice to get it to minimize and especially for low gear. When hills are involved, the coasting speeds of the output can vary so this makes it even more complicated. Downshifting to low gear on flat ground can even be difficult at times .
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Old 06-01-2021, 10:11 AM   #5
Rob Doe
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Default Re: Downshifting problem

Once upon a time, way back in the day, I could kick my A's shifter from 1st to second and 2nd to 3rd. I was 14 or 15. My dad vowed at the supper table that back in his day ... therefore I just had to try it.

My A is new to me. I'm now 70+. I won't be kicking, jerking, or yanking anything on this car. I've recovered most of my shifting skill but certainly not all, and definitely have trouble downshifting to 2nd attempting to climb a hill. It will come back, (hope, hope, hope).

All this said, idle speed has significant effect on shifting speeds i.e. rpm and wheel speeds. If your speedometer doesn't work or is sticking it would not be usable to shift at the recommended ranges. I sometimes count in my head 1, 2, pause, 1, 2 as I double clutch.
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Old 06-01-2021, 11:37 AM   #6
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Default Re: Downshifting problem

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If you can shift up through the gears okay shifting down just requires more practice. I agree with Ray, you have to rev it a lot more than you think you do.
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Old 06-01-2021, 12:28 PM   #7
nkaminar
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Default Re: Downshifting problem

Mitchell sells a synchronized transmission. Second and third are synchronized but not first. There is one intersection where I have to double clutch into first and I have to remember to rev more that I think I should. Their transmission has the same case as a stock Model A and looks the same on the outside. While you are at it, get their overdrive too, which is also synchronized.
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A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.
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Old 06-01-2021, 12:43 PM   #8
Dean Lemoine
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Default Re: Downshifting problem

I have the Mitchell synchronized transmission, absolutely love it.
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Old 06-01-2021, 01:32 PM   #9
1931 flamingo
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Default Re: Downshifting problem

What weight lube in the tranny?? Learning to double clutch is an "art".
Paul in CT I never had too much luck downshifting.
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Old 06-01-2021, 01:41 PM   #10
capete
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Default Re: Downshifting problem

Gear Lub - 85W-140
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Old 06-01-2021, 01:43 PM   #11
Ernie Vitucci
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Default Re: Downshifting problem

Good Afternoon...The Model A Transmission is suppose to have 600 wt oil in it. It is available from all of the Model A Vendors...It might help you to drain, flush and re-fill your transmission with fresh oil...many people put one can of STP in their transmissions...Ernie in Arizona
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Old 06-01-2021, 01:47 PM   #12
Ernie Vitucci
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Default Re: Downshifting problem

Good afternoon again...One more thought (I have a few now and again) you might practice running your A up to say 25 miles an hour in second gear and trying to memorize the vibration and sound of the engine...when double clutching from 3rd to 2nd, you need to duplicate the sound and vibration in order to down shift successfully...Ernie in Arizona
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Old 06-01-2021, 02:01 PM   #13
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Default Re: Downshifting problem

Quote:
Originally Posted by Ernie Vitucci View Post
Good Afternoon...The Model A Transmission is suppose to have 600 wt oil in it. It is available from all of the Model A Vendors...It might help you to drain, flush and re-fill your transmission with fresh oil...many people put one can of STP in their transmissions...Ernie in Arizona
600W does not stand for 600 wt. A lot of people have been complaining about the oil vendors sell foaming?

I run SAE 250 in my trans but may try to 85w140 because that is what the Mitchell calls for. It would be nice to have just one oil.

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Old 06-01-2021, 02:22 PM   #14
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Default Re: Downshifting problem

From a past discussion;

Quote:
Originally Posted by Jim/GA View Post
Read the Ford Dealer Service Bulletins for info on thinning the 600W oil with kerosene for winter.

There is not a "modern SAE 680" oil. The 680 is on the ISO scale. It is a different lab test from the SAE test. See the table below.

"600W oil" was a Mobil Oil trade name for a specific oil they sold, it is NOT 600 WEIGHT oil. Sorry, guys; common misunderstanding. It was called Mobil 600W Steam Cylinder Oil. It was thick, it was sticky. It clings to the flat gear faces of our transmission and differential quite well, which provides an oil cushion between the metal surfaces to prevent wear. It also slows the spinning gears inside the transmission when you shift, eliminating the need for double-clutching for most up-shifts (1st to 2nd, 2nd to 3rd) unless you are drag racing.

IF the original 600W oil was indeed the ISO 680 available today, and I have no documentation to say that it is, then that is equivalent to SAE 190 Gear Oil. There is also a modern version of 600W that is ISO 460. This is close to SAE 140. I need to go to the Benson Ford Research Center to ty to find out what the original ford specification was for this oil.

The figure also helps you equate the ISO 1200 to SAE 250. This chart is very helpful, I refer to one like it a lot.

A multi-viscosity oil might make sense in a cold climate. Remember the numbering system of SAE 75W-140 means it acts like SAE 75 oil in Winter (the W) and like SAE 140 oil in the summer. So that might work well in Alaska. Or 85W-140. Something like that. Remember, Ford did not have these fancy multi-grade oils in 1928-31.

Hope this helps.
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Old 06-01-2021, 02:41 PM   #15
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Default Re: Downshifting problem

85W-140 GL-5. The GL-5 is not recommended for transmissions and rear ends that have brass components. Use GL-1 for your Model T.

"The sulfur-phosphorus extreme pressure additive technology used in Gear Oil GL-5 provides good thermal and oxidation stability. In addition, this lubricant is fortified with rust and corrosion inhibitors, a foam inhibitor, and a pour point depressant."

The 85W-140 will hold up under pressure better than 600W and has better lubricity.
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A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.
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Old 06-01-2021, 02:49 PM   #16
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Default Re: Downshifting problem

Here is a video.
https://youtu.be/rAZ7NZLpewI
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Old 06-01-2021, 03:02 PM   #17
Ed in Maine
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Default Re: Downshifting problem

I never downshift. Why risk chipping a gear unless you just love to get under your car and spending a half day removing the engine to rebuild the transmission! Keep an eye on the traffic ahead and at the first sign of an upcoming stop, take your foot off the gas. After driving my Model T you have to know how impressed the new owners of the Model A were when the car was first introduced. I always feel that modern car owners are missing a wonderful driving experience shifting the Model A, especially listening to the sound of new gears. Ed
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Old 06-01-2021, 07:14 PM   #18
Pete
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Default Re: Downshifting problem

Quote:
Originally Posted by Magoo2 View Post
Other than operator error (which is a real possibility) what are the mechanical issues that would cause gear grinding while downshifting? Just got my 31 CCPU running. Whenever I come to a hill or turn that requires me to downshift I have to come to a complete stop and start off in first gear to prevent grinding of the gears. I’ve tried double clutching and accelerating while in neutral before trying to downshift to a lower gear but it just does not seem to work.
The first thing you need to determine is if your clutch is releasing all the way.
A quick easy way to check is, sitting still with the handbrake set and the engine idling, transmission in neutral, clutch out, push the clutch in and after 2 seconds try to pull the shifft lever into 1st gear. There should be no grinding.
After that assuming you can't get the the 2 associated gears to match speed for a downshift, try buying a 10 minute instruction session at a road racing school. It is not very expensive if they are not busy. They will have you downshifting like a pro when you leave.

A very important thing †o remember, the model A transmission is not very strong so downshifting should only be done at speeds WELL BELOW where you would upshift that gear change.
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Old 06-01-2021, 08:22 PM   #19
old john
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Default Re: Downshifting problem

Just find a truck driver older than you to teach you. you can be very slow down shifting from 3rd to 2nd moving and clutch engaged and moving, slowly move into 2nd gear feeling gears just touching and rev motor and slip it into 2nd gently taught a lot of kids john
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Old 06-02-2021, 07:04 AM   #20
dave hummell
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Default Re: Downshifting problem

If you can't downshift your model a you should try my mack triplex 13 speed no synchronizers. You have to use the throttle and practice gentile use of the shifter no jamming.
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