Finally a cure for the Panhead leaking transmission

Description: leaking transmission solution

Author: saddlebagrail
Date: Fri Mar 29, 2013 9:53 pm
Views: 1991
Category: Projects

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by saddlebagrail » Fri Mar 29, 2013 8:53 pm

Hi Everyone

I am new here and I am starting this new thread on this Panhead forum ,I will talk about the famous 4 speed tranny made by Harley long ago,those type of tranny are almost industructible but have a problem they often leak to the ground.

With this thread I think I am going to show you, that those tranny can also be leak free.

I have been doing this modification for over 15 years now with a lot of satisfied customers,and I feel it might interest many of you....

I will start this new thread with...

Where is the main leaks on those 4 speed tranny occur?

Main leaks occur on the drive side,from either the end seal of the fourth gear,or between the spacer and the gear itself,and sometime both,cause by different thing,the main seal that run over the spacer almost never leak unless the outside of the spacer show some wear on it,and if you use a good seal it is normally leak free.

I have made many modifications on them over the years and finally came up with a nice solution for those of you who are tired of having a spot of oil on the garage floor or elsewhere,when I say a spot it might be more....

This modification to me is not a band aid solution,this is a real solution.

I will try to described the best I can what I did to modify them to achieve a «no more leak » transmission,please wait to reply til I finish my article and give me the time to put all the pictures in a row so you can follow the step by step procedure to finally stop them from leaking,it takes time to do a thread like this, but I think it might worth it,hope you will enjoy it,nice reading,here it is.....

First here is the OEM spacer there is a big seal running over it,that seal is not the problem if properly lubricate.

Here is the gear with the spacer push against the shoulder of the gear.

First problem I have found is that the bushing is often too loose on the main shaft,first thing you have to do is press out the old bushing.

When the old bushing is out, I start by making a new one out of continuous cast bronze 660,why making a new one....those new bushings that came from different companies have not enough materail to clear everything,most of them ,not to say all of them are set at the factory to have minimal material to remove with a reamer and often end up with many spot of material not removed,...if you look at the inside of your bushing after pressing it and the reaming is done,you will notice that it is not machine from all around,...not enough material mean that the bushing is not supporting on the shaft properly....and wear what I do, I am making a new one,with still lot of material left inside,...remember to clean,prime and put green Loctite inside the gear and on the outside of bushing before pressing.

After bushing is press in…note the difference between both an old one and the newly press one I just made.
You will have to slightly polish the main shaft to get rid of small imperfection or use a new shaft if it is too bad…, and then measure carefully everything so you could machine the bushing to achieve minimum clearance, in this case shaft measurement is .999 inch so I machine the bushing to 1.000 inch(reach for .001 to .0015 inch clearance), you can only do it with a boring bar set up on the lathe, special reamer will only be able to machine one size, that’s all.

When everything is properly done I set up the gear in the four jaws chuck to achieve a perfect alignment, you have to make sure that where the bearing run on, is perfect with a dial indicator.
After you have taken care of that,and the gear is in perfect alignment, you could start the machining with a boring bar.

After the inside of the bushing is machine, I continue modifying the end of the gear, here what I do, machining the recess a little bit deeper so I can put 2 seals in the end of the fourth gear instead of only one as OEM, the machining is done with either carbide or ceramic insert, the total depth is 7/16 inch, instead of the 3/16 OEM, you can see the small oil groove inside the bushing not too deep but just enough to lubricate.
Ready to install the 2 new seals inside the end of the fourth gear, remember always clean /prime and put green Loctite on both the 2 small seals.
Since the outside seal will not receive too much oil, I simply put some Castrol synthetics grease between both seals, to make sure the seal outside get lubricate and not dry out.

When your finish with the gear,it is time to take care of the spacer, since the other main problem occur when some of the oil escape between the spacer and the shoulder of the gear, I always make a new type of spacer out of C1144 steel, with an o ring groove inside so that way no oil could escape.

See picture to show you where the o ring is located on the gear.

And the picture of the new spacer to accommodate the old gear.

Here with the o ring inside

When everything is reassemble you will notice that there is now two seals at the end of the fourth gears including machining from all around the bushing with the perfect tolerance and a 100% mating between both parts,100% mating between both parts means it will now take more time to wear out ,if properly lubricate, plus you will end up with an O ring in the spacer to seal between spacer and gear,(No more silicone…)

See gear mounted vertically with nothing more that friction of the 2 seals and close tolerance getting the gear quite tight on the shaft, but still turn freely on the shaft no problems.
Here is the finish job with everything install ready to put the sprocket on,you could not see anything different from the outside, but this will definitely solve your leaking problem.

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