February 4, 2010

Classic Harley 4-Speed Tech – How To Fix The Leaking Tranny

Hi Everyone

I am new to blogging but wanted to share this first article here on how to stop the leaks from the famous 4 speed tranny made by Harley long ago. These old Harley trannys are almost indestructible but have a problem they often leak to the ground. I have been doing this modification for the last 15 years with a lot of satisfied customers, and I feel it might interest many of you….

I will start this articles with…

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 sometimes in both places, caused by different things, the main seal that runs over the spacer almost never leaks unless the outside of the spacer shows some wear 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 anyone tired of having spots of oil on the garage floor or elsewhere

This modification to me is not a band aid solution, this is a real solution. It takes time to do articles like this, but I hope you find them worth it. I hope you will enjoy it

First, here is the OEM spacer. There is a big seal running over it, that seal should not  be the problem if properly lubricated.

 


 

The first problem I have found is that the bushing is often too loose on the main shaft. So the first thing 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? Often the new bushings that came from different companies do not have enough material to clear everything, most of them, but not all, are set at the factory to have minimal material to remove with a reamer, and often end up with many spots 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 machined all around. So there is not enough material, meaning the bushing is not supporting on the shaft properly…. So it will likely wear unevenly. So what I do is make my own with plenty of material left inside. Remember to clean, prime and put green Loctite inside the gear and on the outside of bushing before pressing.

After the bushing is pressed 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 so you could machine the bushing to achieve minimum clearance, in this case shaft measurement is .999 inch. So I machined the bushing to .9997 inch, less than .001 inch of 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 runs 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 machined, I continue modifying the end of the gear. Here I machine 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 synthetic 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 occurs when some of the oil escapse between the spacer and the shoulder of the gear, I always make a new type of spacer out of C1144 steel, with o ring grooves 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.

When everything is reassembled you will notice that there are 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 lubricated, plus you will end up with an O ring in the spacer set between both the end of the shaft and the end of the spline (no more silicone.)

See gear mounted vertically with nothing more than 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 finished job with everything installed and ready to put the sprocket on. You could not see anything different from the outside, but this will definitely solve your leaking problem.

Note: I had tried a tranny with oil inside without the sprocket at the end, and there was no leak after at least 2 months on the floor, hard to believe but proves this modification is working,

Here is a photo of a brand new Andrews gear that I also modified to accept both 2 end seals and new spacer with an O rings.

DSC09836.jpg picture by saddlebagrail

Note: that Andrews gear is now using an O ring seal on the shoulder of their gear, plus my spacer and includes one O ring on that run not far from their O ring, between end of spline and their O ring.

I forgot to mention that there is at least 4 type of spacers (5 if you count the last 4 speed with belt drive system) needed to do that kind of modifications. Depending of the year of your tranny, there is one that is not shown in the picture, so 5 different types of spacers, but they are the same inside diameter.

Hope this helps those of you who have had problems with leaking 4 speed Harley transmissions from early Knucklehead, Panhead or Shovelhead motorcycles.

(saddlebagrail)

Filed under Engine & Transmission, Restoration, Saddlebagrail's blog, Tech by saddlebagrail

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Comments on Classic Harley 4-Speed Tech – How To Fix The Leaking Tranny »

February 6, 2010

Bart 74 @ 2:44 pm

Great fix,We can all agree with the annoying tranny leak,it sucks!.you can put as many seals as Chicago raw hide can make and drums of silicone there is ,but if you don’t resolve the main gear bushing issue its still gonna puke .Did you have to re+re the bushing in the new Andrews gear?.Can you do this fix?, if so how much?,if you can’t could you pass on the dimension of the depth and placement of the o-ring groove that you cut in the spacer. Sin Bart

Bart 74 @ 3:00 pm

Ray,sorry I forgot to mention the maingear spacer in my tranny is part no 35171-37 41 – early 77. Sin Bart

February 7, 2010

ElectraGlideInBlue @ 1:48 am

Exultant first post Ray. You have solved the leaky trans issue in a way anyone can understand.
Thanks

February 8, 2010

Buzz_Kanter @ 8:00 pm

Thanks for sharing and we all look forward to learning more fixes and tricks from you.

March 8, 2010

panacea @ 8:22 pm

Ray, are you starting with a 65 MDG? Mike

August 3, 2010

Knuckle Dave @ 9:43 am

Great article Ray. I’m currently having this very issue. Would you be interested in doing this mod to my trany if I send it to you?
Dave

August 22, 2010

saddlebagrail @ 3:47 pm

Hi Dave

If you are not in a rush with it,and could wait ,I might be able to do it during winter time ,I am only doing this during my spare time,contact me via saddlebagrail@yahoo.ca,hope that help,Ray

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