Pinion gear lash adjustment

ivoryjohn

ivoryjohn

Senior Member
Could someone please go into depth as to what is involved adjusting the lash and what exactly that is when re-installing the drive shaft and pinion gear when installing a Mitchell Overdrive.

Am I even in the ball park......? I envision the adjustment as adjusting the depth that the pinion gear enmeshes with the ring gear. If the gear is too far out on the ring gear it would move slightly when the gear started moving and would thump either forward or reverse. If the pinion were too fare enmeshed it would bind and not lubricate. Adjusting the bearing holding the end of the drive shaft would allow this end play adjustment in or out.


Now what is the lash really and how do I adjust the lash installing the Mitchell overdrive? I have not yet read the instructions included in the kit.
 
John,

I asked the same question a while ago and the consensus was that I should make no adjustment. It was suggested that I just reinstall my original pinion gear on the shortened driveshaft and reassemble, implying that using the original gear would give me my old settings, before the banjo was entered.

I am interested to see if this is still the group opinion, as I was worried that the pinion gear may sit at a different depth on the new drifeshaft (hence the need to check and adjust).

Paul
 
"Now what is the lash really and how do I adjust the lash installing the Mitchell overdrive? I have not yet read the instructions included in the kit."

Now, isn't that just like a guy! LOL:D:p
 
Humble Opinion:

1. First, it looks like it would help greatly to read the Mitchell Overdrive Instructions that cane with the kit before trying anything.

2. Second, so as not to void any manufactirer's written or implied warranty, try to understand how to install the Mitchell Overdrive per the manufacturer's written instructions.

3. Then, try to ask questions about how others interpreted what needs to be done with this Mitchell Overdrive kit, and what was done to achieve a successful installation.

4. For example, just in case Mitchell revised the installation instructions
 
Last edited:
1. Follow the mitchell instructions.
2.See if you can locate anyone close by you can ask to help you, like a local model a club member in your area.
3. Ask some questions after doing #1 and #2.
I have done several, and helped with 4 or 5 others. It goes fairly easily, but you need to do some homework first.
Bob
 
I assume you are going to install a Mitchell overdrive without completely disassembling the rear axle assembly. That being the case, the task is to remove the rear axle assembly from the car. Be sure and use a suitable and safe spring spreader. I would dicourage you from pulling the rear axle assembly with the spring still attached. people do it all the time, but it is extremely dangerous.

After the torque tube has been removed you need a drive shaft puller to pull the drive shaft along with the pinion gear and bearing assembly out of the banjo. Mitchell can provide you with this tool.

The next step is to remove the pinion gear and bearing assembly from the drive shaft. This is done by removing the 15\16" hex nut from the back side of the pinion gear. You will then need some type of puller to remove the pinion gear from the drive shaft. As long as you do not disturb the two large nuts on the pinion gear sleeve, the pre-load on the bearings will remain intact. In many cases the bearings are found loose with no pre-load. You should attempt to re-set the pre-load by feel. It may also be necessary to replace both bearings along with the double bearing race. In either case the preload can be re-set after the pinion gear assembly has been installed on the Mitchell stub shaft. Clamp the stub shaft in a vice and torque the 15\16" hex nut to a nominal 100 ft lbs. The pre-load can then be set by adjusting the two large nuts to obtain a snug rotational feel.

Backlash is adjusted by the number and thickness of banjo gaskets installed. However, if the rear axle assembly has not been disassembled, you do not have that option. Moving the pinion gear fore or aft by adding shims or machining the pinon gear sleeve is not necessary. Henry designed the assembly so that the pinion gear is about in the middle of the ring gear. The only practical option concerning backlash is to move the ring gear closer or farther away from the pinion gear. This is accomplished by shifting gaskets between left and right on the banjo.

There is an article published in the MAFCA magazine, The Restorer, in one of the 2012 publications that details the installation of a Mitchell overdrive without a complete disassembly of the rear axle assembly. The article should walk you through the procedure. I would not be overly concerned about backlash and preload if you are installing the overdrive in a good running Model A.

If you are planning to completely disassemble the rear axle assembly I invite you to use the procedure published on the following web site. www.ocmafc.com. On the menu at the left on the home page scroll to "tech articles" and click. It will bring up a new menu and at the top is my name, click on it and scroll to the article on differential rebuilding. You are welcome to download and print it out.

Tom Endy
 
Tom Endy said:
I assume you are going to install a Mitchell overdrive without completely disassembling the rear axle assembly. That being the case, the task is to remove the rear axle assembly from the car. Be sure and use a suitable and safe spring spreader. I would dicourage you from pulling the rear axle assembly with the spring still attached. people do it all the time, but it is extremely dangerous.

After the torque tube has been removed you need a drive shaft puller to pull the drive shaft along with the pinion gear and bearing assembly out of the banjo. Mitchell can provide you with this tool.

The next step is to remove the pinion gear and bearing assembly from the drive shaft. This is done by removing the 15\16" hex nut from the back side of the pinion gear. You will then need some type of puller to remove the pinion gear from the drive shaft. As long as you do not disturb the two large nuts on the pinion gear sleeve, the pre-load on the bearings will remain intact. In many cases the bearings are found loose with no pre-load. You should attempt to re-set the pre-load by feel. It may also be necessary to replace both bearings along with the double bearing race. In either case the preload can be re-set after the pinion gear assembly has been installed on the Mitchell stub shaft. Clamp the stub shaft in a vice and torque the 15\16" hex nut to a nominal 100 ft lbs. The pre-load can then be set by adjusting the two large nuts to obtain a snug rotational feel.

Backlash is adjusted by the number and thickness of banjo gaskets installed. However, if the rear axle assembly has not been disassembled, you do not have that option. Moving the pinion gear fore or aft by adding shims or machining the pinon gear sleeve is not necessary. Henry designed the assembly so that the pinion gear is about in the middle of the ring gear. The only practical option concerning backlash is to move the ring gear closer or farther away from the pinion gear. This is accomplished by shifting gaskets between left and right on the banjo.

There is an article published in the MAFCA magazine, The Restorer, in one of the 2012 publications that details the installation of a Mitchell overdrive without a complete disassembly of the rear axle assembly. The article should walk you through the procedure. I would not be overly concerned about backlash and preload if you are installing the overdrive in a good running Model A.

If you are planning to completely disassemble the rear axle assembly I invite you to use the procedure published on the following web site. www.ocmafc.com. On the menu at the left on the home page scroll to "tech articles" and click. It will bring up a new menu and at the top is my name, click on it and scroll to the article on differential rebuilding. You are welcome to download and print it out.

Tom Endy
Click to expand...


Thank you very much for your intelligent answer and respectful reply. It is just what I wanted and I appreciate it very much. The fellow that has my car and overdrive is 60 miles away and I don't have access to the instructions.



For those who sought to hijack the posting with biscuit and flaming oil I suggest you stick them up your exhaust pipe with Bob's bent wood!
 
I have yet to disassemble an 'A' rear end. Can the driveshaft and pinion be removed from the center casting without having to remove at least one of the axle housings?
 
ivoryjohn said:
Thank you very much for your intelligent answer and respectful reply. It is just what I wanted and I appreciate it very much. The fellow that has my car and overdrive is 60 miles away and I don't have access to the instructions.



For those who sought to hijack the posting with biscuit and flaming oil I suggest you stick them up your exhaust pipe with Bob's bent wood!
Click to expand...


A great and well deserved reply !
 
Tom, thank you for your helpful instructions.

And to others, yes I have thoroughly read the instuctions. I live close to nobody who has ever done this before. I have not only read the instructions, but have bought all of Les Andrews books and practically memorized them. I have the pinion puller, and more specialized tools for my A. I have been pulling wrenches for nearly 40 years and can disassemble my direct-injected, over-engineered BMW blindfolded, and know all of the fault codes. There are just some questions that arise as I am staring at the banjo and not wanting to damage it. Appreciate your sense of humor, but ivoryjohn and I were just needing a bit of help. No worries....
 
31 Victoria said:
John,

I asked the same question a while ago and the consensus was that I should make no adjustment. It was suggested that I just reinstall my original pinion gear on the shortened driveshaft and reassemble, implying that using the original gear would give me my old settings, before the banjo was entered.

I am interested to see if this is still the group opinion, as I was worried that the pinion gear may sit at a different depth on the new drifeshaft (hence the need to check and adjust).

Paul
Click to expand...

Why not have a set of directions sent to your house.
I would think you would have to check the back lash. Aren't you using different bearings. Is it the same drive shaft. Things happen it is always best to check things after working on them.

The original question did not have much information. Tom is one of the most knowledgeable and help full guy's on here. He gets nothing for helping .
 
Now read Tom Endy's instructions at the Orange county Model A ford Club website and you have all you need.
Still think you need to put your ego in a box and hook up with a knowledgable local model a guy. The old guys would try doing the job, then adapt and modify if they encountered a problem. Next time you can return the favor and help out someone else.
Bob
 
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