Ring Gear in the Oven-Fly Wheel in the Freezer

[Guest]

Soon I will be, amongst other things, changing my Ring Gear.
My plan is to break the old ring gear off the flywheel and send the flywheel off to be faced. (I have managed to chip a few teeth off the ring gear and occasionally have to rock the car in 4th gear to catch a tooth.) I was told that I should put the flywheel in the freezer for three days and when ready, heat the new ring gear in the oven for two hours before "dropping it on the flywheel". Oi Vey, does this work? What temp should the ring gear be heated to and not disturb the hardened teeth? Obviously (I think) the refacing of the flywheel should be done with the old ring gear off.

I have to change the rear oil seal on the crank as well as put in a new clutch so this will be my summer project. That, plus finish the TR3 engine, I have my summer projects cut out for me.


Bill

 

[CraigFL]

I've put many things together with the heat/cold trick but never a ring gear on a flywheel. I can tell you that you won't disturb the heat treatment if you stay below 300 degrees-- you probably only will need about 200 -250 degrees. Have your NOMEX gloves ready!! Just remember that as soon as you take the flywheel out of the freezer and the gear out of the oven they start returning to room temp --- you only have one shot to put them together RIGHT(aligned straight). I would face the flywheel after I put the gear on...

 

[Mickey Richaud]

[ QUOTE ]
What temp should the ring gear be heated to and not disturb the hardened teeth? Bill

[/ QUOTE ]

Not sure - maybe you should check with Martha Stewart...? (Sorry, couldn't resist /ubbthreads/images/graemlins/jester.gif)

Sounds reasonable, though. And I would think you'd have to get the ring gear pretty hot to damage it. Maybe 250?

Mickey

 

[bobh]

Bill,
It should work like a charm. When you heat the ring gear it will expand outward. The inside diameter increases. With the flywheel chilled and the ring gear heated it should drop in place.
You shouls have your flywheel checked for cracks before they resurface it.

 

[dklawson]

Heat treatment usually involves a high temperature process followed by tempering at a lower temperature. Most steels I'm familiar with require this tempering process above 400 degrees F. If you stay below 300 and put the ring gear on a "top shelf" in the oven (away from the element) you should be fine.

I haven't installed a ring-gear either but have worked with some non-automotive shrink fits. As mentioned, you have to work quickly. The flywheel will take longer to come up to temperature than it will for the ring gear to cool down so stage your parts so that your flywheel is waiting on the ring gear and not the other way around. You can also consider buying/making a small Styrofoam box to put the flywheel in and after a day or so in the freezer, put the flywheel in the improvised cooler along with a block of dry-ice. Allow it to cool with the dry ice for an additional hour while the ring gear heats and you'll have a little more margin for error.

BTW, keep a wooden mallet or other soft faced hammer handy to tap the ring gear down. Don't expect it to just drop into place. However, don't use heavy metal hammers or you'll likely damage those nice new teeth.

I'd vote for facing after the new ring gear is on. The shop shouldn't have any problem with this. Any stresses you create during the heating/cooling will be address this way. It would also be a shame to pay to have the flywheel resurfaced and then have an accident or mishap while fitting the ring gear that causes you to have to pay to have it done again.

 

[trfourtune]

put your flywheel in a large zip lock bag with something to absorb moisture before you put it in the freezer. this is to keep ice from forming on the flywheel.when you mate the two parts, pull the bag off at the last second before mating.
rob

 

[piman]

Hello Bill,

for what it's worth, and it is a bit of a fiddle being that the diameter is large and the height low, I just knock the ring onto the flywheel at normal temperatures.

Alec

 

[77_MG_Midget]

Hello Bill,

There was a fairly lengthy discussion on this on the Spridget board awhile back. But, here's the highlights from some of the posts:

Never tried this, but according to my GT6 workshop manual:
"Remove the gear by using a copper drift while supporting the flywheel on wooden blocks. With the engagement face of the teeth facing rearwards, fit a new ring gear by heating it in boiling water, then pressing it onto the flywheel. Use a drift and "G" clamps. Under no circumstances should the ring gear be flame-heated."


my Sprite book says to heat the ring gear to between 572 and 752 degrees Fahrenheit, and then putting it on the flywheel. I normally just use the kitchen oven, and put the flywheel in the freezer overnight.
As far as the removal of the old one, they suggest splitting the gear with a cold chisel. I generally use a cutoff wheel in a die grinder to thin a spot as much as possible, and then, one good whack and it's off.


I've done this many times. Jeff's method is about the same as what I've used. At times have been able to substitute a western Pennsylvania concrete back porch in winter for the freezer, but oven temp at 450°~500°F, some GOOD tongs and a hasty; "MAKE A HOLE!"... ring fairly SLIPS over the flywheel. Just be darned sure which way you put it INTO the oven.

Hope this helps you.

 

[sp53]

Hi Bill the cold shrink hot expand trick works good, but you will still have to force it on a little. What I do is put the flywheel in the freeze and put the ring gear in boiling water. I did not want to get it too hot. If you have some of those kinda heavy duty claps that look like giant clothes pins they will help hold the ring gear on the edge as you pound it on with a hammer and block of wood. The pinch clamps work better than a C clamps because they keep constant pressure on the work. The C clamps will just vibrate off as the ring gear goes on while you pound/tap with the hammer.

Sp53

 

[Guest]

Great tidbits of information! Never was a fan of "you get only one shot at it" situations but let the pieces fall where they may. A little aside, my guru Dave at TRF maintains that essentially all the ring gears on the TR6 were put on backwards at the factory. Hummm, is this possible. Is there a front and a backside to these things?


Bill

 

[77_MG_Midget]

[ QUOTE ]
Hummm, is this possible. Is there a front and a backside to these things?

[/ QUOTE ]

ABSOLUTELY it's possible. There is most definately a front and backside. Again, from my GT6 manual,

"With the engagement face of the teeth facing rearwards,"

-John

 

[CraigFL]

This probably has to do with the chamfer on the teeth for easier engagement with the starter gear.

Although I'm not sure how that relates to what John just said...

 

[sp53]

Hey Bill the early tr3s the rings gears go on different than a tr6 or later tr3 bolt on. The press on models have the chamfer toward the clutch surface because they use the non-bendix type starter. The later tr3 had the teeth on the back and bolted on. So if you take it off make sure you look at the right picture when you put it back on. You should get more than one chance at it also; I know I did.
Sp53