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What type of tool do you need to measure the size of a 4th main?
Posted: Wed Jun 17, 2020 2:15 am
by DHort
I was thinking I should replace the ball cap(4th main) to try to reduce leaking down the drive shaft. It appears that you can get 4 different sizes of ball caps. However, the part of the cap that is babbitted is about 2 1/2 inches inside the hogshead. How do you measure that far inside? Do they make a special micrometer or caliper? Or do you check with feeler gauges before you pull the old one out? Thank you.
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Wed Jun 17, 2020 2:31 am
by Kerry
Ford only had one size for the ball cap, others that are available now are for worn or machined down in size drive plates. You will need to remove the ball cap and measure the shaft of the drive plate to see what you need making sure that it's not out of round from wear.
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Wed Jun 17, 2020 7:48 pm
by Jerry VanOoteghem
DHort wrote: ↑Wed Jun 17, 2020 2:15 am
I was thinking I should replace the ball cap(4th main) to try to reduce leaking down the drive shaft. It appears that you can get 4 different sizes of ball caps. However, the part of the cap that is babbitted is about 2 1/2 inches inside the hogshead. How do you measure that far inside? Do they make a special micrometer or caliper? Or do you check with feeler gauges before you pull the old one out? Thank you.
David,
You would have to remove the ball cap in order to measure its inside diameter. You could use a dial caliper, but a telescope gauge & micrometer would be best. Not everyone has telescope gauges though...
However, what Frank states above is just as important, since knowing what size cap to use is completely governed by the diameter of your output shaft. If we know, or can assume, that the output shaft is not worn, then all you need is a standard size cap. Unfortunately, measuring the shaft, while in the car, can be tricky. I bought a vernier caliper with extra long jaws just for that purpose. Even so, it's very cumbersome, (but not impossible), to get an accurate reading.
You could try just measuring the cap diameter first. If it's well above the standard size, then replacing with a rebuilt, standard size cap will obviously be a big improvement... even if your output shaft is a bit undersize.
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Wed Jun 17, 2020 9:00 pm
by paddy1998
If you have leaking down the driveshaft you might want to also make sure you've got a good seal inside the drive plate shaft.
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Thu Jun 18, 2020 8:51 am
by Mark Nunn
I have a caliper accessory kit to extend the reach of my calipers. It extends the jaw's reach to 2 1/2".
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Thu Jun 18, 2020 5:09 pm
by DHort
- 0-200-mm-outside-groove-caliper-with-flat-points-vernier-caliper-stainless-steel-measuring-instruments.jpg_350x350.jpg (6.79 KiB) Viewed 3602 times
I did not know they made a caliper like this. Might be the way to go. Another suggestion came in to pull off the ball cap to see what the inside dimensions are. If worn, then a standard size would work to reduce the leak, even if the shaft is worn.
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Thu Jun 18, 2020 5:27 pm
by Scott_Conger
reinstall the 4th main several times with an increasing thickness brass shim pack. Use .003" brass shim stock a couple inches long and about 5/8" wide. It is very flexible and you can continue to add shims and install the main until it will not slide down and seat. You now know the ID of the worn main MINUS the shim pack is the OD of the largest part of the tail shaft.
Now, measure the ID of the main with a telescoping gauge and micrometer, finding the smallest area and measure at least two times at that place 90 degrees apart; as per above, that diameter MINUS the shim pack thickness is your tailshaft within .003".
Let Gene French custom bore to size and if necessary, lap to fit with Timesaver Yellow.
Anything else is just messing around and wasting time
Hopefully your tailshaft doesn't spin like a whirling dervish and beat it right out again...that is entirely possible.
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Thu Aug 06, 2020 6:38 pm
by DHort
Scott, all looked good but I put in some Ultra Black to make it better. That should help.
Scott and Jerry
I was advised to try using tapered feeler gauges to see how the fit was. I was able to slide the 0.004 feeler gauge between the 4th main and the tail shaft. I had to work to get the 0.005 feeler gauge between them. That seems to be within tolerance. Maybe I just have too much oil in the pan when I change the oil and the screen in the hogshead directs it to the rear as well. I am guessing 4 quarts is too much. Need to make use of the upper petcock next time.
When I originally separated the drive shaft housing from the 4th main I noticed there wasn't any grease in the housing, just some oil. The universal joint was not dry. I put 10 pumps in there twice a year with the grease gun. Just to double check, while the housing was apart, I tried pumping some grease through the zerk and it went in fine. That way I knew the zerk was not plugged. The leaking oil must dilute it.
I never stop learning with these cars.
Time to get back to doing my Census homework.
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Thu Aug 06, 2020 7:00 pm
by Kerry
10 pumps twice a year wouldn't be enough, the uni joint need to be full of grease every 500 miles.
Re: What type of tool do you need to measure the size of a 4th main?
Posted: Thu Aug 06, 2020 9:07 pm
by Jerry VanOoteghem
DHort wrote: ↑Thu Aug 06, 2020 6:38 pm
Scott, all looked good but I put in some Ultra Black to make it better. That should help.
Scott and Jerry
I was advised to try using tapered feeler gauges to see how the fit was. I was able to slide the 0.004 feeler gauge between the 4th main and the tail shaft. I had to work to get the 0.005 feeler gauge between them. That seems to be within tolerance. Maybe I just have too much oil in the pan when I change the oil and the screen in the hogshead directs it to the rear as well. I am guessing 4 quarts is too much. Need to make use of the upper petcock next time.
When I originally separated the drive shaft housing from the 4th main I noticed there wasn't any grease in the housing, just some oil. The universal joint was not dry. I put 10 pumps in there twice a year with the grease gun. Just to double check, while the housing was apart, I tried pumping some grease through the zerk and it went in fine. That way I knew the zerk was not plugged. The leaking oil must dilute it.
I never stop learning with these cars.
Time to get back to doing my Census homework.
Four quarts is really not too much, but it is about the max. I usually start to get a little out of the top petcock at 3.5 quarts. Then, while I'm not looking, I pour in the extra 1/2 quart. Never an issue.
I'm really not a believer that the screen directs so much extra oil to the rear. There's a huge amount of oil that get thrown back there even without a screen.
There should be a plug in your output shaft, just ahead of the square hole. If the plug is missing, a lot of oil will pass through and into the ball area.