R75/5 final drive puking vent

[ebeeby]

Any ideas why the vent on my final drive started puking? I pulled fill plug and grease level is well below lowest thread. I know it should hold 8 ozs but notes show last time I changed it I could get only 7 ozs in.
I suppose it *could* be the internal seal and I will have a the rear wheel off for a tire change next week...

 

[20774]

I've never measured the amount of gear oil I put it...I just fill to the bottom of the threads. What weight of oil? How do you begin your rides...slow speeds at first or do you immediately get to high speeds? Outside temps can affect things as well.

If the final drive is leaking internally, you probably should see that on the outside. There's a small drain hole that opens up below the axle location on the final drive. This hole angles up and inside a bit of a trough. That way if there was some leakage, it wouldn't foul the brakes and you'd have a chance to see it oozing on the outside.

 

[olironrider]

… actually, there are two(2) “weep” holes on the Rear Drive: one for the outboard seal, one for the inboard seal…



View is “worm’s eye” looking at bottom of rear drive housing. The lower one in this image, is for the outboard or axle nut/washer side of the Crown Gear Seal (#2); the upper one is for the inboard or Crown Gear Drive Spline Seal, also circled in red…



Should the outboard seal fail, gear oil will weep thru the outboard hole, alerting the rider of problems. The inboard seal failing, will be slung-off and drained into a circumferential “trough”, away from the rear brake components, to its weep hole.

I suspect your over-flow is from either the: transmission vent bolt being clogged, the transmission output seal failing, the “V” notch in the transmission rear cover not having been filled in, the rear drive pinion seal failing. There’s a “being pressurized” situation there, forcing oil out the easiest path: rear drive vent.

Both the transmission and rear drive are filled with Gear Oil, not grease, to the level of their respective, threaded oil plug, filling holes. Over-filling can also purge gear oil at rear drive top vent.

Have you checked the gear oil quantity in the Drive Shaft Housing ?

 

[ebeeby]

Thanks for this.
Driveshaft oil normal. Final drive below lowest thread.

 

[20774]

How low below? If just a mm or so, no big deal...the gears will still be running in a bath of oil. I'd refill to the proper level and see how things look like down the road.

 

[olironrider]

“Driveshaft oil normal”… the only reliable way to check the Driveshaft Oil is to drain and measure the quantity; the “using a wire probe thru the driveshaft filling plug on the forward/top of the rear drive housing, and past the shaft to pinion coupling, to dipstick the level” is a poor “Divining Rod”.

Your Long Wheel Base 1973 R 75/5 driveshaft housing (swing arm) should contain up to 150ml of measured oil upon draining; any more than that is cause for investigation: oil migrating from transmission ?

 

[20774]

… actually, there are two(2) “weep” holes on the Rear Drive: one for the outboard seal, one for the inboard seal…

Interesting...I never knew about that lower one. I had to go check my /7...get rid of some dirt/oil ... and there it was! Thanks!!!

 

[ebeeby]

How low below? If just a mm or so, no big deal...the gears will still be running in a bath of oil. I'd refill to the proper level and see how things look like down the road.

Do you believe the proper level is 8 oz or lowest thread?

 

[20774]

My Haynes says 250cc or 8.4oz. To be honest, I never measured, just filled to the bottom thread.

 

[6322]

Actually it varies by model year. Best bet based on riding and servicing airheads for over fifty years is the lowest thread in the fill hole.

 

[olironrider]

… the general opinion regarding the after-market manuals is, that they are best used for starting campfires.

The BMWAG Owner’s Manual supplied with the R 50/5 R 60/5 R 75/5 motorcycle…



A fluid pint is sixteen(16) fluid ounces; “0.5 pints” is eight(8) fluid ounces.

Note: check at normal operating temperature, i.e. after 20-30 minute ride; oil expands in volume when warm.

Fill to “lowest thread of filler opening” if needed then (with motorcycle on center stand).

Copies of the Original Owner’s Manuals are available from suppliers.

 

[ebeeby]

… actually, there are two(2) “weep” holes on the Rear Drive: one for the outboard seal, one for the inboard seal…

View attachment 100043

View is “worm’s eye” looking at bottom of rear drive housing. The lower one in this image, is for the outboard or axle nut/washer side of the Crown Gear Seal (#2); the upper one is for the inboard or Crown Gear Drive Spline Seal, also circled in red…

View attachment 100044

Should the outboard seal fail, gear oil will weep thru the outboard hole, alerting the rider of problems. The inboard seal failing, will be slung-off and drained into a circumferential “trough”, away from the rear brake components, to its weep hole.

I suspect your over-flow is from either the: transmission vent bolt being clogged, the transmission output seal failing, the “V” notch in the transmission rear cover not having been filled in, the rear drive pinion seal failing. There’s a “being pressurized” situation there, forcing oil out the easiest path: rear drive vent.

Both the transmission and rear drive are filled with Gear Oil, not grease, to the level of their respective, threaded oil plug, filling holes. Over-filling can also purge gear oil at rear drive top vent.

Have you checked the gear oil quantity in the Drive Shaft Housing ?

Getting a slight weep from upper drain hole on refurbished final drive I bought. 30 mile highway ride. Very slight weep, I think. Hoping it was just a new/dry seal settling in.

 

[ebeeby]

… actually, there are two(2) “weep” holes on the Rear Drive: one for the outboard seal, one for the inboard seal…

View attachment 100043

View is “worm’s eye” looking at bottom of rear drive housing. The lower one in this image, is for the outboard or axle nut/washer side of the Crown Gear Seal (#2); the upper one is for the inboard or Crown Gear Drive Spline Seal, also circled in red…

View attachment 100044

Should the outboard seal fail, gear oil will weep thru the outboard hole, alerting the rider of problems. The inboard seal failing, will be slung-off and drained into a circumferential “trough”, away from the rear brake components, to its weep hole.

I suspect your over-flow is from either the: transmission vent bolt being clogged, the transmission output seal failing, the “V” notch in the transmission rear cover not having been filled in, the rear drive pinion seal failing. There’s a “being pressurized” situation there, forcing oil out the easiest path: rear drive vent.

Both the transmission and rear drive are filled with Gear Oil, not grease, to the level of their respective, threaded oil plug, filling holes. Over-filling can also purge gear oil at rear drive top vent.

Have you checked the gear oil quantity in the Drive Shaft Housing ?

… actually, there are two(2) “weep” holes on the Rear Drive: one for the outboard seal, one for the inboard seal…

View attachment 100043

View is “worm’s eye” looking at bottom of rear drive housing. The lower one in this image, is for the outboard or axle nut/washer side of the Crown Gear Seal (#2); the upper one is for the inboard or Crown Gear Drive Spline Seal, also circled in red…

View attachment 100044

Should the outboard seal fail, gear oil will weep thru the outboard hole, alerting the rider of problems. The inboard seal failing, will be slung-off and drained into a circumferential “trough”, away from the rear brake components, to its weep hole.

I suspect your over-flow is from either the: transmission vent bolt being clogged, the transmission output seal failing, the “V” notch in the transmission rear cover not having been filled in, the rear drive pinion seal failing. There’s a “being pressurized” situation there, forcing oil out the easiest path: rear drive vent.

Both the transmission and rear drive are filled with Gear Oil, not grease, to the level of their respective, threaded oil plug, filling holes. Over-filling can also purge gear oil at rear drive top vent.

Have you checked the gear oil quantity in the Drive Shaft Housing ?

Getting a slight weep from upper drain hole on refurbished final drive I bought. 30 mile highway ride. Very slight weep, I think. Hoping it was just a new/dry seal settling in.

Did 8 mile mostly highway drive. Dry. 2 hours later did return trip. Dry.

 

[ebeeby]

Did a 40 mile ride this morning - dry. A few hours later, returned, 40 miles, slight weep.
Checked final drive oil level- half way up threads.