915 syncro hubs question

[Roslin]

I made to day 2 special press fixtures, to to use when the syncrohubs on 1.st and 2.nd and 3.rd gear wheel should be removed.

The pres fit seems to be in the area 0.05-0.06 mm and i do not think they could be pressed on in cold condition..?

Have anyone done this before.. and if they are heated then how much ?

Roslin

[john walker's workshop]

it helps to heat them. they pass over the leading edge of the splines easier without distorting the inner race bore. the factory staked the hubs on by slightly deforming the leading edge of the splines after the hub was installed. that's the main issue in getting them started. i use an electric frypan and heat oil to 300° or so.

[garibaldi]

how do the french fries come out?

[Roslin]

Thank you John,

But 300 deg. is that Celsius ? i thought on circular grind a very small chamfer as lead on the splines .. mabye 0.2mm x15deg. to prevent them cut the new hub and mabye easyer to fit.

Roslin

[john walker's workshop]

the staked splines keep them in place. they can work themselves off the gear a bit without it. i've had to carefully trim the leading edge occasionally, but i try not to take all of it off. sometimes you will find that the bearing and it's inner race bind after pressing the hub on over the staked ends of the splines and a sunnen hone is needed to make the bore true again. you don't want bearings overheating and seizing in the gear. uncontrollable rear wheel lockup in worst case scenario.

[boxermania]

Roslin

You can also use your oven to heat up the components. 350 F will, in most cases, provide sufficient expansion for an easy installation.

If you want to take it further, one can calculate the required temperature based on the expansion of steel.....

[Roslin]

Thank you both

your ideas sound right, i will try to do it.

Roslin

[dentist90]

If you have a deep freezer it will also help to put the gear into the freezer for a couple of hours. I set the oven at 250F for the hubs. I just put my 1st and 2nd synchros on without a press. I was able to push the hubs onto the gears about 1/2 way by hand (wearing mechanics gloves, of course) and finished them off with a couple of taps on a block of wood.
If JW is still on this thread, do you recommend re-staking the splines with the new hubs on or do they usually hold OK as is?

[GotaT]

Guys, how did you get the gears and synchros Off to begin the process of replacement?

[dentist90]

Glad you asked! I didn't want to pay $100 for a one-time tool, so I bought two 2 1/2" muffler clamps and two 6" bolts and pounded on a big socket to get them out. 2nd gear took a little more effort as the muffler clamps started to slip out of the synchro hub groove once. Just make sure the clamp gets into the c-clip retainer groove properly, torque the bolts on good and put the whole assembly into a vise or between two blocks of wood. Pictures always help so here you are:




You can see in the third picture how the hub is starting to lift away from the gear. Some minor scuffing of the socket ocurred, but it's still got lots of life left. Socket was only worth $13 anyway. No damage to either gear nor hub this way as well.

[garibaldi]

I used to cut them off using an air powered roary tool with an abrasive disc on it, Id slice in across the face of the synchro on both sides, then just use a cold chisel to crack it off.

[GotaT]

I can understand how you removed the Synchro and hubs once off the shaft, what I mean is how did you pull the Gears off the Shafts to begin? and My next question is how did you put it all back together

[Roslin]

Hi there, thanks for many interesting replays on my question

I have some pictures of how i pressed the gears of the shafts , and how i removed the syncrohubs.

I will be back when i got the pictures ready to upload

Happy New year !

Regards Roslin

[dentist90]

To get the gears off the pinion shaft all you have to do is drop it onto a block of wood on a cement floor (JW uses a soft steel plate instead of wood). The inertia of the gears will push off the pressed on roller bearing at the nose end of the shaft without damaging the bearing. Took only two drops to get mine to come apart. The ball bearing and pinion end roller bearing are still left on. You don't have to remove these to repair 1st and 2nd synchros.
To reassemble the gear stack you will have to press on the nose end roller bearing. Heat the bearing up again in the oven and find a piece of pipe that just slides over the pinion shaft and has same diameter as the INNER race of the bearing and tap it back down the shaft until the gear stack is all nice and snug again if you don't have access to a press large enough.
If you need to rebuild 3rd and 4th synchros it is a bit trickier as you have to get the staked flange nut off the input shaft. Using an old clutch plate over the splined nose of the input shaft can help hold it steady while you try to wrench it loose. You will need to secure the clutch plate in a big a$$ vise or nail it to a tree as you will be applying a lot of torque (maybe 200 ft-lbs or so) to break it loose. Then you can use the same droping technique to get both the roller bearing and ball bearing off the input shaft, but BE CAREFUL not to go nuts and bend the long slender shaft doing this. I think I have to replace the the roller bearing at the diff end of the input shaft due to some scoring so I may be putting this technique to the test. I'd rather not disturb the input shaft. Maybe I'll post a picture of the bearings to get another opinion.

[dentist90]

Before dropping pinion shaft on a block of wood...

... and after two drops...

[GotaT]

Is it necessary to pull off the speedo Gear?
Once the Bearings come off from the drop do the gears just slide off, or do they need to be pressed off or "dropped" also?
And if I understand correctly to put it back together its just a matter of putting the gears and bearings in the freezer for about 2hrs and then Heating the Gears and bearings in a fry pan w/ cooking oil to 300F for X # of minutes... how long?, and then pushing /pressing them back together.

[Jim Sims]

The speedo gear on the end of the shaft doesn't have to come off. Per the factory shop manual, gears and other parts are to be re-assembled on the shafts dry: no oil or grease between the part and the shaft. My experience has been to leave the shaft at room temperature and heat the gears, bearing races, etc. with a hot air gun (no hot oil mess and little risk of over heating as compared to using a gas torch). Then holding the hot gear, etc. with a leather glove they just slip onto the shaft if you move quickly. If you cock the part and jam it and let it cool you'll need a press to push it the rest of the way. Or press if off and start over.

[GotaT]

Hot air gun,... what I might call a Heat gun? Heat the parts resting on a bench for some time and then quickly push them on the shaft? Sounds alot easier then using the cooking oil method. Thanks. Any other experiences?

[Jim Sims]

Wagner heat gun: 750 deg. F and 1000 deg. F air temperature settings. Approximately $30 at local hardware store. I set part on piece of pine 2 x 4 on top of my metal bench vise and blow hot air over the part moving the gun to evenly distribute the heat. Initially used a temperature gage on the part but found that if one heats the part using high setting until the wood below just starts to singe and smoke the correct temperature has been reached. A second person supports (could also support shaft in a soft jaw vise) the shaft vertically as I slip on the parts weather a heavy leather glove. Have all the parts arranged in correct order and orientation before starting.

[boxermania]

I'm not a fan of heating the gears with oil, since the oi splaters, can burn you and can also ignite if you are not careful....like I said before the oven at home is a far better choice.

If the better half has some isues, just wrap the part in aluminum foil and heat it to 350F.....it will slide home without any poblems, but you must be ready and uses leather, or welding gloves.....