I always go with the manufacturer's recommendation in your manual. Over filling can cause leakage of the excess into the rear axle or into the clutch area. With environmental concerns in some areas of the world any leakage is grounds for not licensing a vehicle.
"Over filling can cause leakage of the excess into the rear axle or into the clutch area. With environmental concerns in some areas of the world any leakage is grounds for not licensing a vehicle."
Mike,
I want to pick at you for a second.
Two things:
a. How is the oil going to get to the clutch area? Seems to me that excess oil from the transmission area will flow downhill.
b. If leakage is a governing defect for licensing, then all Chevrolet 207s, 216s, 235s and 261 will not qualify after 1k miles. So "a" above is not a concern. You won't be driving a car equipped with any of those engines anyway.
Overfilling the transmission can cause oil migration into rear axle, thereby overfilling the rear axle which can force oil past wheel bearing seals, eventually contaminating the rear brake linings which may cause loss of braking performance. It doesn't hurt to raise the viscosity of the trans and diff fluids by adding some Lucas Oil stabilizer which is mineral based and roughly SAE 100+. There are some schools of thought that urge folks to use the mineral based lubricants to avoid issues with yellow metals, like brass, in the drivetrain. The Sulfur in some diff oils can cause yellow metal degradation is the claim. Mineral oils have no additives like Sulfur. Not much to lose by using the mineral oils, unless you are going to drive your car in sub-zero weather.
The fill port on my transmission is on the lower right side, pointing up at about a 45 degree angle. I fill it to the bottom of the treads in the hole. No problems yet. When in doubt, after filling the trans, check the oil level in the rear axle. Go for a 30 minute drive until the fluids are warmed up. Then recheck the fluid levels. Mine is just up to the bottom of the threads at the diff, also. Repeat the fluid check process often until you're confident there is no oil migration to the differential. If the differential oil runs out when the plug is removed, and the trans level is low, the answer is obvious that oil is migrating from trans to diff. and the seal in your pilot bearing is not effective. Either the seal is worn out and/or your torque tube brass pilot bearing is worn too much. Unfortunately the pilot bearing is held in place with a rivet that is difficult to remove and salvage for reuse. You won't see diff lube migrating to the brakes unless the axle seals/bearings are worn and sloppy. As I recall, I replaced the axle seals when I did the final drive change, and puling the axles required that I modify my wheel puller strategy since the slide hammer trick required its own modification to work successfully. You can make your own puller if you have a large diameter piece of tubing and a flat steel plate. The tubing needs to be just larger than the axle bearing, yet smaller than the axle flange. It need to be cut short enough to allow the axle shaft to stick out such that when you drill a 3/4 in. hole in the middle of the flat plate, the threaded part of the axle just sticks through. Then you slide the tube over the axle, the plate over the threaded part of the shaft, and install the axle nut. You tighten the nut to slowly extract the axle. The only issue is that the nut and axle threads must be really free so the axle desn't rotate when turning the nut. You might need an access hole in the side of the tube or a fairly narrow, yet thick flat plate, so you can insert a pair of pliers to hold the axle from rotating.
I think he is talking about the U Joint ball area. You should add a few ounces and the fluid from the transmission will add more, once you drive it some.
My 1951 1 Ton is now on the road! My 38 Master 4 Door is also now on the road .
I like adding my transmission fluid using the port for the speedometer gear. I use a small oil can with a pump to squirt the transmission fluid in. On page 10 of my 41 manual it recommends this method Universal Joint Lubrication
Per Charlie's comment: maybe I am wrong, but when I was having problems with chatter from my clutch I was finding a very thick oil dripping down my flywheel on the transmission side. When I disassembled my transmission it was plain to see that the front bearing could easily let excess oil pass through it. There is no way to trap this excessive oil in the transmission, that's why I recommend that you follow the manufacturer's recommendation of 1 1/2 Pts.
Charlie, in Germany you would not be able to obtain a license plate for a vehicle leaking oil.
When I replaced my front bearing I replaced it with one that had a bearing cover built into it on the flywheel side.
From the Filling Station's driveshaft bushing how-to:
Quote
CAUTION: When the ball housing and U-joint are installed, it is vital that gear oil is filled before operation. Check and fill the transmission with gear oil. The ball housing has its own fill plug at the top of the back of the transmission housing. If there is no plug on top, some transmissions have to be filled through the speedometer drive gear hole. About ½ pint of gear oil will be required to lubricate the U-joint.
There is an oil passage on the back side toward the transmission that excessive oil can escape without it going anywhere near the clutch mechanism. Thing is there is little to none that needs to escape if the transmission is not over-filled. You don't need to fill either the transmission or the differential above what you can touch with a curve? pinkie.
As to filling the U-joint, there is no need. The needle or brass bearings are well lubricated with grease. That will last for plenty of time for the oil from the transmission to reach and fill the capacity. Excessive oil in there will slowly travel toward ” he differential. When you take the U-joint out merely make sure that the bearings/bushings are well lubed. There is no need to pull the stinkin' speedometer gear but simply check the transmission with you pinky and fill it until you can touch it. The manual is correct but that step is not needed.
Adding to the transmission and differential to make it thicker so it won't get to the axle seals is futile. Over filling will try to escape no matter the thickness of the oil. Sawdust may help.
You all with more time on your hands than the folks at the rest homes worry too much.
You are welcome to this sage advice. There is no charge.
I must correct my previous post on this subject. On page 119 of the 1939 shop manual it gives the instruction to fill the universal ball housing through the ground strap hole.
My 1951 1 Ton is now on the road! My 38 Master 4 Door is also now on the road .
hi all yes there is a bolt opposite the speedo drive i put the oil in there i removed the gear box filling bung and it was over filled so it looks like the oil from the ball joint can make its way to gear box so i allowed the oil to drain out replaced filling plug and went for a 60 k drive all is good the car is a lot quieter with a new u joint and torque tube bearing and it looks like i have fixed my clutch shudder which is why i pulled it apart thanks tony
Great! Yes, the transmission and u-joint do share oil, I think the concern is that if the u-joint ball starts out empty, the u-joint can destroy itself in a short distance, or so I have been told. Eventually the oil does migrate between the two.
This should help clarify Mike's comment about oil getting to the clutch.
His concern is that same as mine. If you fill the u-joint ball and then fill the transmission before you drive the car you will potentially create an overfill condition. As noted when you drive the car the gear oil flows back and forth between those 2 areas until things equalize.
The problem occurs because there is no seal on the front input shaft bearing. There is a slinger to that keeps oil away from that bearing. However, a slinger only works when the input shaft is rotating. If the car is parked with an overfull transmission oil will flow out the front of the transmission into the clutch area.
I remember my father telling me that he ruined the clutch in a '48 Chevy when he parked the car headed downhill on a steep slope. Oil flowed out around the front bearing and on to the pressure plate and clutch.
