I was informed the other day that the Ruckstell book recommends to torque the drive shaft pinion nut to at least 70 foot-pound. I looked up the information today and it does says this on page 13. This information is not correct. The drive shaft nut should be torqued to a minimum of 150 foot-pounds. If the slots in the castle nut do not line up with the hole in the drive shaft tighten the nut until they do.(NEVER BACK OFF PRESSURE) If the nut strips, good it was junk. If the drive shaft strips, good it was junk. In the stock application this is your brakes, the pinion needs to drive off the taper of the shaft to work correctly.
I grab the square end in my vice and tighten the pinion gear nut as tight as I can get it. So far so good .
The MTFCA front/rear axle book also says "as tight as possible, at least 70 ft-lbs." (page 20).
Glenn Chaffin / Stan Howe, you guys have redone literally tons of rear axles, what say ye?
Mike, Where did you get 150 Foot Pounds? That is absurd. The Ford shop manual does no give a torque figure. It says to draw on the nut tightly against the gear. That's all it says. I feel 70 Foot Pounds is fine. We have used this for every Ruckstell we have ever built and have never had a problem. 150 lbs will strip the threads.
The torque for a 5/8" grade 2 bolt is around 150 ft/lbs. A drive shaft and the nut are more like grade 8 which can easily handle over 200 ft/lbs.
As best I remember the castle nut on the driveshaft is thinner than a standard nut. The threads of the nut are stronger than the threads of the screw, both parts being the same steel strength. On the axle shafts the nut is thicker and I do torque these to about 120 ft lbs. I doubt I have ever tightened a driveshaft nut to 150 ft lbs.
Old nuts are closer to grade 8. The last ones I bought were made out of some kind of cold rolled crap that was so soft you could practically nick it with a fingernail. I have always tried to save the old ones and reuse them.
I put the gear on, stand it up on end and put a socket on the gear over the nut and give it a good whack with a bfh, check to make sure it is tight on the shaft and give it couple more. That will seat it far better than tightening the nut will. IMHO, all the nut is for is to keep it from coming off, it if is on the taper the way it should be the nut is just extra insurance.
It is also very critical to make sure you have the correct Woodruff key. The standard key is too tall and will hold the gear off the taper a few thousandths. Make sure you use a correct key and that the gear seats down on the taper. I do not reuse old driveshafts unless that taper is perfect or I can clean it up to where I feel it is safe.
Your mileage may vary.
So Ted, why do you say the threads of the nut are stronger than the threads of the screw? I never really thought about that before.
The root diameter of the nut is large compared to the root diameter of the screw. Thus the root area for the nut is much larger than the root area of the screw, so the external thread is stronger.
From my experience I've only ruined threads on the nut when 150 lbs of torque is applied. Of the many differentials I've assembled I can count on my left hand the number failed nuts and it is less than 5. To say 150 lbs of torque is absurd is an absurd statement. I just did a driveshaft last night and applied more that 150lbs on a brand new nut with no issues. I've got three cars in my garage that are holding 150lb torque. 2 of which run in the Montana 500 and the other one has a Ruckstell.
Like others say, I place the square end of the DS in a vise and tighten the nut as tight as I can. I use a cheater bar and socket. I don't know about ft lbs of torque and could care less. I get it pretty damned tight. If I had to choose, I'd say 70ft lbs is about right. That's a lot of torque. I don't know how someone would get 150 ft lbs with ordinary tools. But what do I know?
Well your chart may prove me wrong but I still say it is absurd. 70 Foot Pounds is really tight and we have never had a problem doing that. If the nut is good and tight and you have the cotter pin in place the nut isn't going anywhere and won't come loose. The drive shafts are not grade 8 and I don't believe the nuts are either. I would rather tighten the nut to 70 and avoid stripping the threads and having to buy another new drive shaft. Do what you want but I know what works and am sticking with 70 Foot pounds.
Thanks, Ted. I should have thought of that but I am getting old and senile and tired and not as fat as I used to be. So I'm thinking if I jump up and down on an 18 inch bar with a socket on the end of it to tighten the nut and now weigh 260 instead of the 310 I used to weigh, does that mean if I strip the nut I need to lose more weight or use a shorter bar??? Beats me but that's the way I tighten them. That's after I smack it the gear several times with a BFH.
I doubt if they even had torque specifications back in T days. I'll go with Glen. I've been doing them all my adult life, and never torqued them once, and never had one loosen up either. I agree with Stan on the woodruff keys. Use the old ones.
Original rucks specs.
I wouldn't call less than half the recommended torque "very tight". 70 ft. lbs. isn't even enough for a main bearing bolt.
Stan, could you measure your velocity before and after contact and give us an estimate of the time you are in contact with the bar. With that data and knowing your mass we could calculate the change in momentum and using the time in contact we can then calculate the force and thus the torque. Alternately, we could just say they are very tight.
Tom, Ford never had any torque specifications. He just said to tighten the nuts tightly then cotter pin them. That's exactly what we do and it works every time. It's a Model T not a drag racer. There is no need for all of this over analysis of torques and specifications. Sure some specifications are important like Triple gear bearing clearance but there is even a big disgreement over that between the so called experts. But with regards to the Drive shaft nut, Stan is right. The most important thing is to make sure that the pinion gear is seated on the taper and not being held up by a key which is too tall. Once the gear is properly seated on the Drive shaft taper it will no longer move as long as the nut is tight. It doesn't have to be 150 Foot Pounds. It just has to be tight. How many farmers had a torque wrench. Even Ford didn't have a torque wrench. How many loose pinion gears have you ever heard of? None, so why even talk about 150 Foot pounds? I believe this is called overkill.
When I rebuilt the back axle on the 14 touring, I tightened to 70 lb/ft the continued to tighten until the hole lined up for the split pin. At the time I watched the torque dial and it was at 105. I have mentioned this to several restorers and none have told me it was not tight enough until now. Like Glen, I would like to see some contemporary justification for the 150 lb/ft figure.
How many Drive Shaft nut torque failures have you seen in the last 100 years? The nut is seated on the taper. After the nut is seated on the taper it can't go anywhere unless the nut comes loose. The nut holds the pinion in place and will not come loose unless you remove or forget to install the cotter pin. The amount of torque makes no difference in the results. What a waste of time, I'm our of here. Do what you want.
Glen, there are failures. The problem is that 70 lbs. is not enough pressure to properly seat the pinion onto the taper. Consequently, the pinion is being driven by the key rather than the friction of the taper. When the brakes are applied the pinion can split because it is being driven by the key rather than the taper. It is not all that uncommon. I have seen this many times.
Hey guys, When you install a new chuck on your drill press you place a 2x4 under the chuck and bring down the spindle and tap it into the 2x4 a couple of times and you are done. There is no key way at all and we drill for years and the chuck stays in place. Thats because it,s a holding taper. You are wedging the chuck onto the tapered pin. And if you replace the tapered pin you will see that the end going into the spindle is very short. No nuts or key ways and things stay in place for years. Clamping a head bolt or main cap is a lot different. We know that to many hubs have been over tightened as there is a need for shims or longer axles. Same thing. To much pressure will open up the taper. So why do you think you need to pull your guts out on this nut? Scott
The need to "pull out your guts" is to keep the pinion gear from splitting because it fails to drive on the taper. 150lbs can be done easily with a torque wrench. Many of you are all talking through your hat. 150lbs is less than the recommended torque for a grade 8 bolt. Case in point- Bill Mullins from Spokane torqued a pinion to 70lbs of a differential he built(following the repair manual instructions), drove it for many (lets say 3) years, sold the car to Dennis Powers of Iowa, the pinion gear failed last year. I on the other hand, torqued a pinion to 150 pounds 15 years ago and it is still working fine. This is includes nearly 10,000 miles at 50mph or faster. In fact I tore the differential down 2 years ago to convert the housings to large drum and the pinion gear and nut were in perfect order! I'm just making you aware that the torque spec isn't acceptable in the repair manual. My professional recommendation is torque to 150lbs and reduce the risk of failure that may lead to an unfortunate hospital stay.
I should note, that pinion gears split all the time; even when properly torqued. For example, when Mark Auto was cutting gears and they cut the key way inline with a tooth, There were many failures of those gears. I've seen failed gears when too much engine torque was applied (burnouts, hopped up engines with hard starts on pavement)
I'm not calling out Glen personally. I am saying the article should be adjusted. It is filled with tons of great and helpful information. I am letting the community know this is an area I don't agree with and I think should be noted for future builds.
Mike, you keep citing the torque specs for a "grade 8 bolt". We are not talking about a "bolt". We are talking about a castle nut that is a grade five at best (original Ford nut and not the crappy soft reproductions) and no where near the height of a standard nut (less thread surface per inch) not to mention approximately a third of the nut thread surface is lost because it is castellated. If you review the Ford Service Manual, it shows the small T shaped factory wrench used to tighten the pinion nut. I doubt very seriously you would ever be able to tighten the nut to 150 foot pounds with a similar tool. The reality is how much torque is necessary to adequately seat the pinion on the taper before we begin distorting and damaging parts? This does make for great debate but, I'm also with the 70 to 75 torque crowd.
I didn't pay Mark to side with me and I lied when I said I'm out of here. You have me sucked in. Tom, you are wrong. If the taper of the shaft and pinion are both good and not damaged the pinion will seat on the taper by hand. It takes very little force to keep it there. 70 Foot pounds is more than enough to keep it there. The photo in the Ford shop manual, page 149 shows a nut being tightened with a Ford tool with two handles. Neither handle appears to be more than a foot long. How could you torque to 150 pounds with that tool? Most torque wrenches are near twice that long. You can torque to what ever you want but I see no need to change the manual on opinion when hundreds of rear axles have been assembled this way with no problems. It is curious why Tom has seen a lot of failures in Washington and we have not in California. That tells me that there must be a lot of poor mechanics in Washington.
The Ford spec for tightening the drive shaft nut is: Install the pinion. "The pinion is then drawn tightly on tapered end of shaft, by running on the drive shaft nut and drawing it tightly against pinion. The nut is then locked with a cotter key" That is exactly what we do in the manual except we have added 70 Foot Pounds. The nut has to be drawn down very tightly to achieve 70 Foot Pounds so we are doing exactly what Ford said and more. As Mark noted above this is not a grade 8 nut or shaft so the specs above do not apply. And the nut is not a full nut it is a short half size nut and at least half of that is castellated so there are few threads to torque. Your torque specs do not apply to this nut. Sorry Tom about the pun about Washington mechanics but I couldn't resist. I'm BAD.
There are two different styles of genuine Ford D.S. Pinion Nuts too, early and late.
Larry, Thanks for your support. Us old timers know what works.
Ok, I went and tightened a drive shaft nut against a pinion gear as tight as I could with a 1 foot bar. I was able to get 80 Foot Pounds, When I did the same thing for writing the book I only got 70 Foot Pounds. But that is no where close to 150 Foot Pounds. To get 150 Pounds you would have to use at least a two foot long bar and beat on it with a mallet like Stan Howe.
Stan Howe is a mallett?
Let me clarify what I do. Or did. I don't do any Ruckstell work for anybody but myself these days. There is no money in it. It is too much work, parts are too expensive and the supply of them in Montana has dried up. If I can ever get time to list them I'll be selling off all my extra stuff like parts and junk related to them. .
However, I do not tighten the nut super tight. Tight but not super tight. You define what super tight is, I know what I do. I stand the driveshaft on the square end on block of wood. I install the key and the gear. I install the nut loosely. Standing on a stool, I place a large, heavy impact socket over the nut. I give it a hell of a whack on the end of the socket. With a BFH. Then I give it a couple more for good measure. Then I tighten the nut. I use the same breaker bar to do it I have been using for probably 50 years with a short socket on it. It is about 15 inches long. I clamp the driveshaft in the vice, just back of the jaws I put an 18 inch pipe wrench to keep it from turning. Then I put the breaker bar on the nut and lean on it pretty hard. That tightens it until just before it strips. If the hole lines up I put a cotter pin in it. If it doesn't like up I drill another hole. Then I put the cotter pin in.
Smacking it with the BFH seats the taper. If it won't do that it isn't going to hold no matter how much you tighten the nut.
Contrary to what a friend of mine does, I do not use an impact wrench, only the socket to smack it with. I do not use a torque wrench. I do not know what the torque is and I don't care. That sucker is tight when I get done.
I once worked with a German installing a short cycle flooring press and he had two torque values:
1. Strong tight
2. Very strong tight
Stan , I'm with you I don't care what the torque is I just tighten it until it is good and tight and that is good enough. It is just a coincidence that that is 70-80 pounds.
Stan, I put the square end of the drive shaft in a bench vise then tighten the nut as tight as I can get it with a breaker bar about 1.5 feet long. that gives me plenty of leverage to get it tight. It ain't moving or going to break a pinion. Never has and I don't expect it ever will. never had a problem.
I would bet a nickel that what Stan and Glen just described is well over 70 ft. lbs.
Hence the "at least 70 ft. lbs." wording in the rear axle books....
"Well over 70 lbs" is not the same thing as "at least 70 lbs."
Tightening the nut with a wrench with a foot long handle like Ford did nets 70-80 Foot Pounds. I find nothing wrong with using 70-100 Foot Pounds. That is really tight. But 150 Pounds is overkill and way too much.
Mark, 70 Pounds is really tight and works well. The nut is not going to come loose especially with a cotter pin. More torque is ok but not necessary. As I Said before 150 pounds is absurd.
If a quart of agent orange with kill an entire forest then a 55 gallon drum will really do the job
Ok, I have two of the original Ford tools for tightening the Drive Shaft nut. The torque you get depends on how strong you are. The wrench handles are 7 inches long, not 12. . I am a strong 80 years old. I was able to get 100 Foot pounds with the wrench but I really had to lay into it. I still believe that anything between 70 and 100 is good. Our original recommendation of 70 Foot Pounds, minimum was based on one test. If it makes you happy I can amend the book to recommend 70-100 but not 150.
THE AGENT ORANGE MUST HAVE KILLED THE HORSE.
Just finished a Fordor sedan this year. I followed the Ford instructions and with a 12" breaker bar got the nut to what I felt vas "very tight." New 12 tooth pinyon and good appearing taper. Out for a test drive I misjudged a traffic light and had to stand on the brakes. The result was a loud bang and I coasted through the light with no brakes. On tear down I found the woodruf key had sheared in two. A new key in place the nut was tightened with an 18" breaker bar. On the Annual tour to Cochrane I had to lockup the rear wheels on a steep hill at Lake Louise, still holding just fine. I have rebuilt several axles using the "very tight" method without problem. Maybe this once was because of a too large Woodruf key or just one of those things, but I suggest a spare pair of shorts whenever you are out in a T!
I believe that the original keys are tempered or at least better then the ones that are available.
If your key shears that means that the pinion was driving on the key rather than the taper, which means that your nut was not tight enough.
*disclaimer* I'm not saying one should use a soft key or leave the key out.