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Transmission leak

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doc308
Posts: 171
Joined: Mon Apr 07, 2008 8:43 pm
Bikes: 1948 Harley EL
1959 Harley Sportster XLCH
2016 Harley Softail Slim FLS
Location: cohoes, ny

Transmission leak

#1

Post by doc308 » Sat Apr 17, 2010 5:50 pm

I had my 1950 , 4-speed tranny completely rebuilt this winter and was advised to fill it with 75w90 semi-synthetic tranny fluid. On the first ride, the mainshaft seal began to leak badly and it's been leaking ever since, even when the bike is just sitting. ( By the way, the bike doesn't lean way over on the stand).

Q #1---when I filled it with with oil, I accidentally overfilled by about 4 ounces . I subsequently drained it and refilled with the proper 1 1/2 pints, but it still leaks. Would the 4 extra ounces be enough to blow a brand new seal?

Q#2--what about the weight of the oil? I remember years ago when we just used straight up 50 wt motor oil. Is this 75w90 too heavy an oil for these old tranny seals ? Same q re: the synthetic aspect of it--ie , is synthetic too slippery for the seals used in these transmissions and tend to leak past them. Should I give a try to the old SAE oil before pulling everything apart again to replace the seal or is it basically too late for that?



drinner-okc
Posts: 182
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Re: Transmission leak

#2

Post by drinner-okc » Sat Apr 17, 2010 11:19 pm

Doc, How sure are you the leak is between the seal and the Main Drive spacer? Look closely
and make sure the seal is in the case far enough that the lip is inside the notch for the L-shaped key. If not, it's cut the seal & it's wasted. Another leak people overlook is caused
by wear on the inside lip of the spacer from the ends of the roller bearings. Do you know if the main drive bushing was replaced & sized to your mainshaft? If it is loose there, even a -65 drivegear with the seal will leak there because the wobble on the shaft makes a mini oil pump to the outside.
If you go back inside the box, you might check out the main drive spacers for sale over on
caimag.com by 'saddlebagrail' they have an o-ring groove INSIDE and seal on the main drive gear. A shop I worked at did that to a few dedicated leakers long ago, just never thought it would have any commercial value.
Your original 50 case would have had a "tin hat" cover on the end of the counter shaft.
make sure it sits flat and is not distorted. If you remove it, dolly the rim flat around the screws. Use some brake cleaner to clean the end of the shaft & case bushing, then put some quality RTV sealant on the end of the shaft & work it smooth. Then reinstall the gasket & cover. Also make sure your vent screw is not blocked, and in a hole that goes all the way
thru the case so it can breathe.
Last but least, my 2 cents, the 75w90 is too thick to flow between the clearances in places like the countershaft gear, thrust washer & case bushings. At least in temps this time of year.
In my Pans, I change the trans oil like the motor oil, 50wt fall/winter, 60wt spring/summer.
Good luck and good riding!

biker_k
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Re: Transmission leak

#3

Post by biker_k » Mon Apr 19, 2010 6:51 pm

75w90 is too thick. It plugs the tranny vent holes and as a result the seals will leak. Remove the vent plug, blow it out, drain the tranny and put a pint of 10w in it to try to "cut" the gear oil. Then run some 50wt motor oil in the tranny and you should be ok. It might leak for awhile and seal back up, but if it doesn't, then you are going to have to replace the seals also, which means more of a tear down.

doc308
Posts: 171
Joined: Mon Apr 07, 2008 8:43 pm
Bikes: 1948 Harley EL
1959 Harley Sportster XLCH
2016 Harley Softail Slim FLS
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Re: Transmission leak

#4

Post by doc308 » Mon Apr 19, 2010 7:19 pm

Where is the vent plug ?

Bosheff
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Re: Transmission leak

#5

Post by Bosheff » Mon Apr 19, 2010 8:38 pm

On a 50 it should be located between the kicker cover and shifter cover directly on top of the tranny case itself. It will probably be a hex shaped affair with a hole located on one of the flats, which may or may not be visible. Just unscrew it from the case and check to see if it's clear. Drain the gear lube and use either 50 or 60. It wouldn't hurt to flush after runnin it a bit to evacuate as much of the gear lube as possible. Gear lube is just to heavy....bosheff

fourthgear
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Re: Transmission leak

#6

Post by fourthgear » Mon Apr 19, 2010 10:33 pm

Well ,I use Syn. 75-90 in the cooler months & 75-140 in the hot months in all three of my bikes (2 Pans & 1 ultra )& have no problems . Don't let the weight numbers fool ya ,they are not as you might think they mean .

You can cause leaks in the tranny by over filling or a pluged vent , but the GEAR oil will not cause any by itself.
Most leaks from that area are cause by out of spec components or inproper assem..

Try the super nut , but if out of spec main shaft bushing in the main drive gear , it will eat all seals in time .

Cotten
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Location: Central Illinois

Re: Transmission leak

#7

Post by Cotten » Mon Apr 19, 2010 11:32 pm

Don't forget that "supernuts" are a bandaid repair for when a '65 and later maindrive gear is used without a seal, and a '65 and later clutch hub as well.

They interfere with OEM-design hardware for all previous years:
Been there, done that, and regretted every minute attempting it.

....Cotten

fourthgear
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Location: north florida

Re: Transmission leak

#8

Post by fourthgear » Tue Apr 20, 2010 11:46 pm

There are a lot of people using them with great results ( on pre - 1965 systems )as long as all components are to spec..Even the 65& up seal will not work if things are out of spec..(ie; main shaft bushing )
You can not use the super nut on alum. inner primarys unless you do some machining to it.

NightShift
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Re: Transmission leak

#9

Post by NightShift » Wed Apr 21, 2010 4:49 pm

Dear Fourthgear,
All those people using them with great results cant be using panhead clutch hubs and drive gears because two things cant occupy the same space at the same time. Look at how the seal in the nut sticks way out inside. That has to stick into the end of the shovel gear on the right, where a seal is supposed to go.
STUPDNUT.jpg
Look at the real Pan gear on the left where there is no shoulder for a seal. The supernut seal would just pucker out if you tighten the nut because its got no place to go.
And a real Pan clutch hub has a big nub on it that gets in the way too.
STPIDNUT.jpg
Anybody running a supernut aint running Pan hardware.

Respectfully submitted,
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fourthgear
Posts: 1390
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Location: north florida

Re: Transmission leak

#10

Post by fourthgear » Wed Apr 21, 2010 11:24 pm

NightShift wrote:Dear Fourthgear,
All those people using them with great results cant be using panhead clutch hubs and drive gears because two things cant occupy the same space at the same time. Look at how the seal in the nut sticks way out inside. That has to stick into the end of the shovel gear on the right, where a seal is supposed to go.
STUPDNUT.jpg
Last time I looked ,that sproket nut (super nut also ) tightens up the drive sproket & will not come into contact with the end of the main drive gear.
Look at the real Pan gear on the left where there is no shoulder for a seal. The supernut seal would just pucker out if you tighten the nut because its got no place to go.
The seal (on the super nut ) just seals the main shaft & has nothing to do with the main drive gear seal. two diff. seals sealing two diff. shafts ,so to speak. Don't know where you are comming from about the pucker out thing . .
And a real Pan clutch hub has a big nub on it that gets in the way too.
STPIDNUT.jpg
Now that may be true . How many out there running OEM clutch baskets ?Maybe a lot but , if you look ,most have been changed through out the years.
Anybody running a supernut aint running Pan hardware.

Respectfully submitted,

Cotten
Posts: 6911
Joined: Mon Aug 26, 2002 9:09 am
Location: Central Illinois

Re: Transmission leak

#11

Post by Cotten » Thu Apr 22, 2010 12:51 am

fourthgear wrote:
The seal (on the super nut ) just seals the main shaft & has nothing to do with the main drive gear seal. two diff. seals sealing two diff. shafts ,so to speak. Don't know where you are comming from about the pucker out thing . .
Fourthgear!

Forget the big seal.
This is about the little seal inside the gear from '65 on.
It must be removed for the supernut's lip to extend inside.
And a real Pan gear through '64 won't take it at all.

The "supernut" is just an expensive bandaid for worn seals, if you had one.
If, as you posted, it does not work with aluminum primaries either, then it is entirely limited to temporary repairs on machines equipt with both later hub and drive gear, but no support bearing or primary housing.

I agree that there are many,
as anything built out of a catolog would be!

If your mainshaft is regularly wearing out this gear's end seal, the supernut seal will probably not last longer.
Better find a Dixie dealer, because they distribute the replacement seals for the supernuts quite reasonably.

....Cotten

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