MTFCA Forum

Recently I've helped a number of our club's new Model T owners with assessing the mechanical condition of their purchases. One common problem we found were rear axles that needed replacement - most damaged by the axle nut not being tight enough. Cracks radiating from the key slot, worn slots, corrosion / damage on the taper, etc., were the most common reasons.

You want the rear axle nuts really tight - I torque them to the max setting on my torque wrench (75 Ft-lbs) then tighten the castle nut to the next slot using a breaker bar and socket. You'd think there was no way that wheel could ever loosen up but drive it a bit and it will. Put a wrench on it again and I guarantee the nut will move a lot easier than you would expect. Tighten it again to the next slot in the nut. Checking it periodically will save your axles. Be sure you put the wheel on the axle without lube - in fact, clean the mating surfaces with a solvent before assembly.

I've attached a photo taken at a friends business where he was getting ready to repair some Model T rear ends in an assembly-line manner. Five of those sets of axles come from cars I was helping on.

I rarely have a T come here for repair that has the rear hubs properly tight. Not coincidentally, most rear ends I take apart do not have axles I would use for something I would build for myself or put my name on for someone else. It is imperative you keep these things tight. 75lbs/ft at least. If you can’t get that kind of torque then the threads on the axles, nuts, or both have failed. Your safety is at stake here. If you don’t have to use a hub puller to get the wheels off, you are inviting trouble. It’s that simple. New axles are a hundred bucks and change, and they are nice products. They can be had with a little extra length to compensate for hubs worn by loose nuts, and also give a little more room for installation of accessory brakes, also a good idea.

I like around 100 pounds. Anymore than 125 is unnecessary and can probably strip the axle depending on the threads. No torque values were really given for any of the parts on these cars, judgement was what guided mechanics.

I'd say 9 out of 10 that I encounter @ our annual inspection/service events era loose.

I have found it necessary to re-tighten axle nuts a minimum of 3 times unless the hubs/axle tapers are lapped in.
Unlapped tapers have high spots that get worked down & loosen the fit.

& yes, very tight, high torque. The Ford Z tool is around 2' long. I use a 2' breaker bar with a 6 point socket & only use good original nuts, then add a 3' pipe to get to the next cotter pin hole. This assumes a good looking thread on the axle. Re-torque in 50-100 miles. I am much more conservative servicing a customer with shakey threads. That axle needs replacing.

"new" plated nuts are undersized compared to original nuts. Easier to strip a thread.

I will quote Dave Stroud in case he does not comment. "Tighten the nut as much as you can. Then tighten some more."

I think the main cause of the problem stems from many years of running too loose. Over time the axle and the inside of the hub become worn and also the keyway gets worn which causes even a tight axle to move a bit from quick starts and stops which eventually wears it down even more.
Norm

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If the axle, key, keyways, and hub bore are on spec and fully-seated, they will stay tight. I would expect new parts, or mixed older parts in good condition, to require several checks and re-tightenings before they become fully seated. It might be a good idea to heat the hub assembly to 200 F or so immediately before assembly and first tightening. I don't think an assembly with oil, rust, or dirt on the axle or hub bore can be expected to stay tight. A poorly-fitted key invites trouble.

A little more to the story.... our club has been having "T-Parties" where we gather at a members house to do some work on their car and "educate" them. Like I said, we have a number of guys brand new to Model T's. I went to demonstrate a hub puller on a newly-purchased roadster and the wheel came off while I was turning the puller on. The key slot was so wallowed out you could flick the key out with your finger. Rx - new axles. Makes me wonder if a pre-purchase inspection shouldn't involve jacking the rear wheels up and pulling the wheels? Of course, that only tells you about the axles and outer axle seals...nothing about the thrust washers, hyatts, etc.

After reading these threads I decided to get me some peace of mind, so this afternoon I went out and pulled the wire wheels off the rear (they been on about a year) and checked the nuts they were just as tight as when I installed them. Peace O mind attained. Jim

Years ago, when MTFCI did pre-tour vehicle inspections on their Annual Tour, and when I was involved in those inspections, the "A number 1" thing we found was loose rear hubs! Scary!

The other instance I recall, was noticing that a guy's steering gear box cover had fully unscrewed. I simply reached over, plucked off his steering wheel, handed it to him, and suggested he "tighten that up a bit." Yikes...

Oldav8tor wrote: ↑

Sun Aug 07, 2022 5:16 pm

A little more to the story.... our club has been having "T-Parties" where we gather at a members house to do some work on their car and "educate" them. Like I said, we have a number of guys brand new to Model T's. I went to demonstrate a hub puller on a newly-purchased roadster and the wheel came off while I was turning the puller on. The key slot was so wallowed out you could flick the key out with your finger. Rx - new axles. Makes me wonder if a pre-purchase inspection shouldn't involve jacking the rear wheels up and pulling the wheels? Of course, that only tells you about the axles and outer axle seals...nothing about the thrust washers, hyatts, etc.

Its safe to ASUME there will be an issue. But, if you are going to pay a premium price, yes have the seller consent.
Any thing over 6K for a 20's open car. Under 5k mechanical issues are expected.

I analyzed clamp load, stress, and torque associated with the rear axle nut using arithmetic and a slide rule My conclusion is that 140 ft lb torque is a safe level. This assumes the axle and nut threads and nut face are clean and dry. Lubrication greatly adds to the clamp load and consequently the stress at the axle thread.

I don't recommend turning the nut to the next key slot unless just a very little turn is necessary. Either select a washer or grind the face of the nut. From slot to slot, the nut location changes about .0095 inches.

Art Mirtes

speedytinc wrote: ↑

Sun Aug 07, 2022 6:16 pm

Oldav8tor wrote: ↑

Sun Aug 07, 2022 5:16 pm

A little more to the story.... our club has been having "T-Parties" where we gather at a members house to do some work on their car and "educate" them. Like I said, we have a number of guys brand new to Model T's. I went to demonstrate a hub puller on a newly-purchased roadster and the wheel came off while I was turning the puller on. The key slot was so wallowed out you could flick the key out with your finger. Rx - new axles. Makes me wonder if a pre-purchase inspection shouldn't involve jacking the rear wheels up and pulling the wheels? Of course, that only tells you about the axles and outer axle seals...nothing about the thrust washers, hyatts, etc.

Its safe to ASUME there will be an issue. But, if you are going to pay a premium price, yes have the seller consent.
Any thing over 6K for a 20's open car. Under 5k mechanical issues are expected.

Sure for us that have been around old cars, we know what to look for. People that have NEVER been around them or have not done much mechanical work, have no clue what they are looking at or for. So, it is not safe to assume anything, they would not know what to look for.

Note to Tim Juhl: Thank you for posting this important safety check reminder.
Yesterday after reading it, I went right to my workshop and checked my favorite T and sure enough, one needed 1/2 of a turn to reach 90 ft. lbs. and the other side was ok.

Thanks again, Tim

Keith

Thank You Tim.

Checked the Can Crusher TT today. Yep, BOTH were loose. RIght one about 5/8 turn and Left one about 3/8 turn.

Had you not posted, I would have never checked since I thought my late best friend would have torqued them properly. AND, never thought they would/could loosen.

Terry

Excellent reminder Tim! I need to check my own work from 4-5 yrs ago.

I just got back from a great time at the Michigan Jamboree. Prior to going I checked my axle nuts again and they were good this time and didn't require any additional tightening. This was after 600 miles on the MTFCI national tour. Nonetheless, I'll check them at least once a year just to be safe.

I started this thread because I was seeing axle damage on all the cars I worked on and was told by people I respect how this was a common problem on the cars they see. I am new to the hobby but have benefited from the knowledge and help of more experienced T'ers and felt it important to pass such knowledge on. There is so much that is unique to the Model T that we must share it with those new to the hobby and hope they will do the same. It also doesn't hurt to remind long-time T owners of such problems. This forum is a great example of how that sharing of knowledge takes place and I'm glad to do my part.

Cant help myself on this one, one of the issues with rear axle nuts coming loose is the threads are worn out. I found on a model A forum once where a guy had a axle nut come off on a tour. When he tried to tighten the nut he found it would not tighten up. The solution he came up with was to rethread the axle to 9/16 ( same # of threads per inch) and put a 9/16 nut on the new threads. I have found this to be a very good way to save axles that have poor threads but otherwise are good. I only have a couple of thousand miles on the ones I did so I will keep you posted on the results.
Craig.

Tim J said
" Cracks radiating from the key slot, worn slots, corrosion / damage on the taper, etc., were the most common reasons."

These things were most likely caused by loose hubs on the axle because the nuts weren't tightened properly in the first place. Once the cycles began, fractures and wear made the nut and hub more loose, and more looseness made the damage worse. From then, one begets the other.

We must remember that model Ts were produced at a time when most adults were raised in an era where such dependence and use of machinery was a new thing! They were not so familiar with "proper procedures" for mechanical assembly. That, coupled with poor roads and resulting lower speeds made the consequences of poor assembly practices less severe. So there was not so much pressure to learn to do thing right! The initial damage to many of our parts began before we were even born! We therefore need to be more vigilant in watching out for these issues.

Thank you Tim J especially, and all as well.

What an informative thread. I'm going to go check mine. The rear end was my next project anyway.

Well Jesus Take the wheel!!! I looked. No cotter pin and the nut was on finger tight. Good thing I only test drove the car!!!

Yes, informative thread that caused me to check my axle nuts prior to the famous Texas T Party next month. Took the right rear wire wheel off the Tudor and removed cotter pin. Thought I’d slip upon 90 torque pounds and set my torque wrench at 70. Moved one of the castellations over the cotter hole. Set at 80 and axle nut didn’t move. Set at 90 and the nut didn’t move. Question: Can I now back off to install cotter pin between original 2 castellations ?
Many thanks

I would advance the nut to the next slot. If you are in doubt as to the integrity of the threads, remove the nut and take about .005" off the face, or use a machine washer under the nut and face the washer if necessary.

Nut wouldn’t budge to the next slot. Researched old Forums and read Jerry Van O advised ‘face off’ nut on 320 wet/dry so I did. Only took 5-6 passes and nut lined up with cotter hole at 90 fp torque. Ford only used 18”-24” iron box end to tighten. No torque wrench. Read where some torque as little as 70; others torque 240.. wow!

Once read in a manual that you should tighten the nut sufficiently tight to prevent it from coming loose. What more info do you need.
Craig.

70 is recommended by wheelwrights looking to make new wheels to replace lost ones; 240 is recommended by mechanics who need the work.

an 18" breaker bar pulled tight and then to the next notch for the cotter pin is sufficient. Recheck in 20 miles and you're golden

I own one of the factory wrenches that tightened this nut in the factory...I'm not looking at it, but bet it isn't even 20" long, AND the box end is still in great shape.

The TT rear axle wrench is a beast but that is a whole different thread for another day

I said before and I say it again - 90 to 100 pounds is more than sufficient. Most problems happen when people don't check back on them after the hub settles on the taper.

Re: "Most problems happen when people don't check back on them after the hub settles on the taper."

This bears repeating.