I'm attempting to put my Ruckstell together and have reached the all important pinion and ring gear clearance step. I've got my Fun Projects adjustable pinion bearing spool set (it might be a shade too deep, but it's awful close to perfect based on the book saying the beveled surfaces of the ring and pinion should be flush).
However, I still have way too much lash. Unless I'm reading my dial indicator way wrong, it looks like I have .038". Y'all tell me what you see.
You need to cut it in half.
shoot for .016+.
.012 to .020 is just fine.
If you set the backlash too tight you risk throwing teeth at speed.
I like to set the backlash at .020.
I don't know if that means something is worn a lot, or what. I don't mind getting two of the .015" shims if that's the way to fix it. That'd put me around .008" which is in the range the Ruckstell book recommends.
Ok, so to do that, would you recommend two of the .010" shims? That'd put it around .018"
Is that a 40 tooth crown, or 39 tooth?
If it is 39 tooth, you will need to trim the small end of the pinion gear teeth so it will clear the crown gear bolts.
Keith it's a 39 tooth - I read that in the book and will make sure to grind the tips of the teeth. Just wanted to see how things lined up first.
I put a shim under the ball bearing to set the clearance,likely 0.010" or less but I really don't remember. You don't want to get carried away shimming under the ball bearing or you may have problems shifting the Ruckstell.
It does not matter at this point a rats backside how much backlash you have- you need to check the contact pattern of the gear teeth with some prussian blue or other marking compound. With your indicator at an angle like that you actually have considerably more than .038 backlash. Move the ring gear toward the pinion about .025" and then check the contact pattern.
Dan - ok, so my question is: can I stack shims? Is there a limit to how many I can/should use?
Also - with some Prussian blue what should the contact pattern look like? At the moment the only thing I have to go off of is the Chaffin's Ruckstell book. I'm wide open to any and all input.
Seth- I only use shims to get the gears into position and then make/modify the bronze thrust washers according to what is needed to 1) get the ring gear into the correct position and 2) set the side thrust on the left side housing. My experience with shims has always been less than satisfactory in the long term. The attached picture shows what a correct contact pattern looks like. Most folks tend to use way too much marking compound and that keeps you from seeing the true pattern. I use a mixture of lube oil mixed with white lead applied very lightly with an acid brush, but that is not politically correct these days.
Seth, the last Ruckstell I checked out had 3 shims under the ball race, showed no signs of any problems and had been in this T since 1963.
Ted Aschman's Tinkerin' Tips Volume two shows diagrams of the way contact patterns look with various degrees of mesh. There is a comprehensive text to go with them.
Hope this helps.
Allan from down under.
The ring and pinion clearance described in the Ruckstell repair book on page 32 says " 0.008 to 0.012 inch maximum is more practical "
Dennis K Anderson
I would put a shim between the ball bearing and the bronze plate. It shouldn't cause any problems there. I have a shim under the ring gear on mine, but if I were doing it over, I would replace that with one under the ball bearing. Although I haven't had any problems with mine, I have heard the shim under the ring gear can cut the ring gear bolts. I understand that the ring gear needs to fit tight against the bell to prevent any possible movement.
Dennis- I am looking in Chaffin's new catalog (PDF). I can not seem to find the shim "between the ball bearing and the bronze plate". Do you happen to know a source? Or, can it be made in the shop?
Seth- I have steel shims to place between the ball bearing and the bronze plate- pretty sure .015 and .020 thick. Sorry, I missed that you were not working on a stock rear end.
If you have an adjustable pinion bearing why would you need shims? Why not "adjust" it?
YES, 100% EXACTLY CORRECT!!! This concentration on how much backlash totally ignores the most important thing: HOW WELL DO THE GEARS MESH! If you get the mesh correct, the backlash will take care of itself, however, the inverse of that rule is NOT true. THANK YOU!
There is nothing you can do to change the mesh pattern of the gears. That depends on how the gears are cut. Yes it is a good idea to check it but if it is bad you have to change the gears. You should never put shims under the ball bearing or P147 notch plate. This makes one axle longer than the other and affects the mesh of the shifting gears. There is no problem with using shims under the ring gear. If the bolts are torqued properly you will not have any movement of the gear or shim. I have always used shims under the ring gear and have never had a problem. with hundreds of Ruckstell's. Your Ring gear is a 39 tooth and you must grind off the ends of the pinion teeth. We do that automatically on the 12 and 13 tooth pinions that we make to avoid this problem
Tim - Seth has the Fun Project adjustable version and it's only adjustable in-out, I think, and the pinion shouldn't really go much more inwards it seems.
There is another adjustable pinion bearing available from Model T Ranch and it looks like it has more adjustments available to avoid shims. Haven't seen myself how it works, though? http://modeltranch.com/show_product.asp?idProduct=41
Roger I have one of those. It is easy to set up.
Dennis K Anderson
I have used the adjustable pinion kit from Model T Ranch multiple times with excellent results.
That adjustable pinion from Model T Ranch looks like the business. However! I've got what I've got. I'll be purchasing 2 shims .015" thick to go between the bell and ring gear. That should put me around .010". I'll see what kind of pattern I'm making there and then work on getting the other housing on with the brass thrust washer.
"There is nothing you can do to change the mesh pattern of the gears."
If that's true, then why bother with alignment at all?
Seth, as far as a shim for between the ball bearing and the bronze plate, you can use a thrust bearing shim, but the center hole will have to be opened up some to fit. I did one for Rickie awhile back. I screwed it to a block of wood and held it in the lathe. The shims are pretty hard, but you don't have to take much out. You could also do it with a dremel tool and a sanding drum.
I've always used Stoltz bearings. Came in handy when I bought a hacked up warford setup.
"There is nothing you can do to change the mesh pattern of the gears. That depends on how the gears are cut." Sorry Glen, I have to respectfully disagree with that statement- it also has just as much to do with how the gears are mounted. If the mounting does not duplicate the same cone distances that the gears were cut to (or worn to) the contact pattern will be incorrect and the only way to get it correct is to change the mounting distances. This is standard industry practice with all bevel gear sets- both automotive and industrial. Yes, there are adjustments on bevel gear generators to modify the tooth bearing, but these are used to obtain a given contact pattern during the manufacturing process. The mountings still need to be adjusted to duplicate that contact pattern during installation.
Seth, Using shims under the ring gear is a very bad idea. Do the job right and be safe for you and others. You run the risk of shearing the ring gear bolts with the use of shims. Listen to Dan and get it right. Many bad fixes have been done over the years. A lot of them work for a long time. But you have the chance to do it right and SAFE. Iam sure you will think things thru before you jump. If you have a race buddy close by they can show you how to get the gears to mesh the right back lash. Good luck, Scott
I agree with Dan McEachern. If you are using new gears, then the lash should be as close as you can get to the book, however, if you have used gears, there is sometimes a ridge worn on one edge of the teeth and you need to fit it with Prussian Blue. The object is to get a good contact pattern and avoid running on the high places caused by former wear. When you get everything as you think it should be, turn the driveshaft. It should run smoothly. If it turns bumpy, you need further adjustment.
Ok just tell me how you are going to change the Mesh pattern of gears. It is built into the cutting of the gears. The differential Housings and the Drive shaft flanges are machined so that the Drive shaft is at 90 degrees to the differential housings. That should properly align the gears without any adjustments except for clearance. Scott, I have never seen a ring gear shim shear a ring gear bolt. That is nonsense. We have probably sold 10.000 ring gear shims and have never had a complaint. The only thing that will damage a ring gear bolt is to not properly tighten them. That I have seen.
Seth, just an idle question: when you mounted the driveshaft, did you also connect at least one of the radius rods? That will ensure that whatever lash you achieve remains the same at final assembly.
Also, the more parallel the dial indicator shaft is with the ring gear, the more realistic the reading.
When Dan uses the term mesh, he's talking about the contact pattern between the two gears. The relative position of each gear will effect the contact pattern. A bad contact pattern will result in a noisy gear set and premature wear, regardless of what backlash has been established. A proper contact pattern will result in the gears meshing properly, with little noise, smooth operation and long life.
Glen, I see that you are a good salesman. Scott
Jerry and Dan, could you please explain how the contact pattern can be changed by moving either the pinion or the crown gears. I thought I had a fair understanding of the Model T differential, but simply cannot understand this procedure, so I'm missing something. The driveshaft center line should intersect the center line of the two axles ( assuming that nothing is bent and the two radius rods are adjusted properly) so the two gear center lines must meet at 90 degrees in both planes. If that assumption is correct, moving the crown gear away from the pinion or moving the pinion gear away from the crown will only increase the clearance, but the teeth in contact must still run parallel to each other although the contact surfaces will show up closer to the top of each gear tooth. Also if the pinion is moved forward enough there will be less of the tooth in contact (along it's length) with the teeth of the crown, but they still have to be parallel. I can totally understand the need for "blueing" with hypoid gears where the pinion meets the crown off center and the teeth on both the crown and pinion are not straight, but I can't visualize the need or benefit of blueing in the case of a Model T. Would this blueing procedure have been part of the assembly process at the factory? Please help me understand this. Thanks in advance : Bruce
The Ford straight cut gears are easy to please but Dan is right, the mesh should be the first set up and is done by in or out of the pinion, once right with luck the lash might come in on spec, but if not moving the pinion in or out only stuffs up the mesh, setting the lash should be done on the brass thrusts.
Thanks, Frank. That's the info supplied by Ted in Tinkerin' Tips 2. His article goes further into how to adjust this.
I find that once the depth of the mesh of the pinion and ring gear are set, the contact pattern is adjustable by juggling the bronze thrusts and steel thrust washers. To make these adjustments easier, I always machine the bronze thrusts to different thicknesses when setting up the diff assembly. That way there are more ways to alter the 'adjustment'.
Allan from down under.
Glen is correct. Think of it like a 8-32 nut and a 6-32 screw. The threads will mesh correctly because they are cut to the same pitch. However the fit will be sloppy, this is not the mesh but tolerances. The tolerances are what you are adjusting with shims and radius rods.
In Frank's illustration above, the condition shown in figures #3 & #4 are corrected by moving the pinion in or out. Conditions #5 & #6 are corrected by moving the ring gear right or left, (by modifying the bronze thrust washers).
Ignoring all of this, and paying attention only to backlash, will not result in a smooth running gear set.
It's the figure 6 which causes the ridge on the gear. The part of the gear which is shown by the lines will wear more than the part which is not in mesh. Then later if you take apart the assembly and put it back together you must create the same mesh pattern or you will have rapid wear and possible shearing of the teeth due to pressure on a small area. It will also run very rough until the ridge has worn off. Better still would be to replace the gears with new or better gears.
That's why it's always a crap shoot mixing up used gears, unless they look REALLY good!
Ford never blued gears. He wouldn't waste the time. The gears are cut to mesh properly. The only way you could change the proper mesh would be to cock the drive shaft to one side or the other and that wold be a stupid thing to do. Ford also set the gears up with more than necessary clearance. THis caused the gears to wear faster but eliminated any problems with assembly. Mismatched gears may not have an optimum mesh pattern but they will work. What happens is the high spots of the gears will make contact first but the gears will still turn freely if you have the proper clearance. As time goes on the gear surfaces will wear and the contact pattern will increase due to wear. In other words the gears will lap themselves in. I have mixed and matched many gear sets and they all worked just fine. .
Glen is absolutely correct. When a T rear end is put together it is impossible for it not to work!
How well it wears, and how noisy it is, is something else.
Allan from down under.