MTFCA Forum

I recently rebuilt the whole front axle and steering parts on my Runabout. It was prone to a severe wobble at around 12-14 mph. I replaced the steering gearbox, gears, steering column shaft, pitman arm, steering bracket bushing, wood block behind the bracket, Anco adjustable drag link caps with solid, shackles, every bolt on the axle, wheel bearings, spindle- and spindle-arm bushings and a few other odd items I can't think of at the moment. There is no looseness in the assembly now. We took a short drive yesterday (about 15 miles) and we still had a severe wobble at low speeds whenever we hit a bump of any size. I would slow to a crawl to make it stop but it would return at the next bump. It was fine after we were on fresh smooth asphalt for the last 6 miles home but the wobble returned in my driveway.

I know that my left spring perch is not properly aligned with the spring. It's rotated slightly and the shackle is binding. That makes the axle assembly shift to the left when hitting a bump and initiating the wobble. That condition was not present with worn out shackle bolts. I need to get a hydraulic press to loosen the perch. It took weeks of fire, hand sledge and penetrant to remove the right perch. I was replacing that one and didn't care about damaging it. I don't want to do the same since I want to save the left perch.

Upon further study, I discovered that my right front wheel has 1 1/2" NEGATIVE camber. It's tipped in at the top and I did not notice that until now. I suspect that could also contribute to the problem of wobble. I want to straighten this axle if possible since I've put a lot into it, including Dan Hatch's repair inserts. Do you think the axle can be straightened with a press?
You can see a dip between the perch hole and yoke in this photo. I had not noticed that before. I'm having difficulty visualizing how I could support the axle in a press and get enough force to straighten it. Any thoughts you may have would be appreciated.

The dip may be an original flaw. The axle is more likely bent between the spring perch holes. Regardless, it can probably be straightened by working on the area between the perches, rather than the very strong short section between the spring perch hole and the end of the axle. Also, be sure your wheels/tires are in good shape.

I think it would be very difficult to straighten the front axle so that the perch hole and fork are in the proper position. Add to that these axles are very hard to straighten on a press. I tried to straighten a slight twist in one a few years back and couldn't do it. I think starting over with another axle is the only practical solution.

Exactly where the axle is distorted would need to be determined by measurement. The car won't handle right unless all steering angles are correct. The spring perch holes in the axle must not be worn or distorted, and the radius rod assembly must be straight. The motor mounts also play a role in steering stability, and they need to be in good shape with all parts present and the bolts tightened as per spec. Rusty, stiff springs will degrade ride quality and can affect steering stability.

First thing you need is a set of alignment rods to install in the perch holes and king pin holes. This will tell you where the problem is if you have one.
Than you can straighten the axle from there. With out a set of pins you are shooting in the dark. Dan

To answer your question : Yes a Model T axle can be cold straightened with a 20 ton press. Use all the above advice first in your preparation

I agree with Dan Hatch. You must first determine whether the holes in the axle are aligned, then you can decide where the axle is bent. There is also a right and a left perch. They must be in the correct position so that you get positive castor on both wheels. Even a sagging frame on one side can cause the ball joint in the radius rod to shift to one side or the other. which will cause the wheels to pull to one side. See your owner's manual to determine the proper specifications.
Norm

If you can find a truck shop that will work on your T, most have equipment to cold bend straight axles. The little axle in your T should be easy for them.

I don’t think the springs are stiff. They are clean and have some sort of antifriction layer between leaves. I had not considered motor mount and radius rod connections to the engine as contributors to wobble. I installed wood blocks in motor mounts and I welded and ground the wishbone’s ball back to size. The socket and cap at the wishbone are in good shape. The cap is new and fits nicely.

I have another axle that is still attached to springs, radius rod, spindles, etc. I will strip that one down and compare it to what’s on the car. That could quickly highlight any bent areas before removing the axle from the car. If that spare looks better, I will start checking that one for straightness. I already know the spindles are showing positive camber. At least that is a start.

The problem with a sagging frame is that it usually sags on one side. Several indicators could be a hood which is crooked because the top of the radiator is on a different angle from the firewall. Or doors which do not fit properly. However, sometimes the body is shimmed up or the radiator has been raised on one side to compensate. The sag will cause the ball joint to go to one side or the other and so will pull the axle back on one side or forward on the other side. An indicator would be steering which pulls to one side and you need to pull the steering wheel a bit to one side to compensate.
I would not try to bend the axle until I was sure it was bent and where the bend was and also which way it is bent.
Norm

A lot of good info on checking axle straightness in old posts. This one implies you would need a 75 Ton press to fix a bend between the perch and spindle. http://www.mtfca.com/discus/messages/17 ... 1323764885

Mark,

Although it's a good idea to get the axle geometry set as good as possible I suggest that this is probably not the primary source of your wobble.

In my experience wobble, such as you describe, is more likely to be due to play in the steering/suspension system, often coupled with buckled and/or out-of-balance wheels. This is exacerbated at low speed when you have large-diameter wheels with some mass.

It doesn't take a lot of play to permit or encourage this issue. If it were me I would, first, go through every component of the wheel and steering system and reduce the play to an absolute minimum. This includes wheel bearings, rod ends, steering arm etc. In the interests of diagnosing the issue I'd be happy to initially slightly overtighten some of these items as necessary in order to completely remove play and determine if this affects or resolves the issue. For instance where you might usually tighten wheel bearings, then back off 'till there's just a little movement, I'd just tighten to a point of no play but still leaving the wheel reasonably free to spin.

This may be sufficient and is worth testing. However, as part of the above, I'd also consider balancing the wheels after first determining that they are not bent or buckled. There are various ways of balancing but a simple static balance is quite adequate in my view. I see people here describing the use of 'balance beads', which I've no experience of, however they may also assist.

BTW, I realise you've said that you have extensively overhauled various components, however it may be that some still have a little play...

Luke.

The camber in the front wheel can be corrected in the car with no dis-assembly. I would correct it first before looking at any re building.
You need a body, suspension shop which an tie a car down. This may be more in the league of a truck repair shop where they are used to working on beam axles. If the axle is chained down outboard of the spring perch, and jacking force is applied inboard of the perch, the axle will bend upwards at the jack point, resulting in the spindle bolt being laid out at the top. You should be aiming for a difference of 1.5' between the wheel top to bottom.

If the problem persists, and everything else is up to snuff, then it may mean a replacement axle. Given the apparent sharp bend in such a short section of the axle, it may be easier to replace the axle than try any further correction to the one you have.

Hope this helps.
Allan from down under.

First, determine by careful measurement exactly where and to what degree the axle is bent. Also make sure the spindle/knuckle is not bent. The T axles were never completely uniform in shape, and what does indeed look like a bend may not be. FWIW, I've driven cars with lots of slack in suspension/steering parts and gross misalignment. They'd skin the tread off the front tires, but they did not shimmy or wobble unless a wheel was bent or a tire way out of balance or out of round.

Did your car drive straight and steer properly before? If so, leave it alone. I assume it did, because you said you never noticed the bend before. If you attempt to straighten it with the bend so close to the spindle and twist the spindles out of alignment, it may be damaged beyond repair. Jim Patrick

The last drive is the 5th time i've had it on the road in over 3 years of owning it. Several trips on my long driveway always end up with the death wobble. When my uncle owned it he never went into high gear. He just drove in parades. The car is just worn out.

Mark, once you look the axle over with a set of alignment bars, I think you'll find the fix to be relatively easy. The likelihood of the axle being bent between the spindle and perch is almost nil (despite the appearance of the deviation on the axle). If it IS bent there, it would have taken a blow that would all but take the axle out of the car.

Scott, I used a 50" woodworking square to eyeball the angle of the spindle bolts relative to the perch mounting surfaces. I know, it's not alignment bars but fairly accurate and easy to use on the car. The left side spindle bolt is perpendicular to the axle, which it should be. The right spindle bolt is angled inward at the top noticeably. I don't need alignment bars to confirm. I have another axle that I will strip down and evaluate for suitability.

Mark

I haved no doubt that the one spindle pin is bent "in". What I doubt is that all of the bend is confined to the small area between the perch mount and the yoke. I highly suspect that if you put bars in, you would find that if there is a bend, both the yoke and the perch are in fact parallel and the bend is somewhere inboard toward the center of the axle.

Now, if the axle was horrendously worn at the top, and the Stevens Tool constantly sought out that wear and was not compensated for during the reaming process, then I could believe that the Stevens bushing is in fact offset, giving the negative camber. I love my Stevens tool, but that is the one weakness that I can see with it and in fact have had one axle that simply had to be fixtured in my mill as it was clear that the Stevens tool was not going to put the bushing in the proper place. This may be what happened to you, as well.

In any event, you are going to really appreciate having a good stable platform under you once you get this sorted out. Good luck

Rather good earlier post on finding problems with bent front axles, good info.


http://www.mtfca.com/discus/messages/17 ... 1323764885

A few months ago I took my unrepaired axle to my local club meeting. (A club member, and forum member known by many, offered to use his Stevens tool to repair it.) One person at the meeting commented that he felt the axle had a lot more sway in the middle than he was used to seeing. I should have taken that as a warning that something was wrong.

It's possible your axle is bent between the spring perch holes, which usually can be corrected.

which further leads to my opinion that it is not bent at the end, but the middle toward the offending yoke, and unfortunately, the only way to fix is to pull the perches and put in 4 alignment rods. You could probably cheat and just use two, but that will not detect fore/aft bends and there is an excellent chance that the car has been unceremoniously yanked and pulled by another car sometime in it's life. The good news is that it is very fix-able. Nearly every T on the road has a tweaked front axle unless it was found and fixed before things went south. It's just the nature of the beast.

How is the camber set with the axle of of the car?

Allan from down under.

Camber is both defined by and set by the spindles under the assumption that the axle is square/true and undamaged. The kingpins in the axle should be parallel to each other and perpendicular to the ground when viewed from the front or rear. Spindles on '26-27 cars have about 1.5 degrees of camber and earlier spindles have about 3 degrees of camber built into them, meaning that the bushed trunnion is not square to the stub axle...the stub axle is biased downward toward the end in order to set the wheel's camber. A bent or bowed axle (either up or down) can throw off camber by tilting the kingpins one way or another irrespective of the caster built into the wishbone.

Now for some trivia: everything from Ford literature showing a cutaway of the front hub and kingpin, to Martin Vowell's superb drawing both show the kingpin inclined inboard and the stub axle parallel to the ground. Don't believe them for a second. In both instances they are skillful artist renderings but are not mechanical drawings and are as accurate as Ford's beautiful advertising brochure of a two-lever, 3 pedal car.

I have earlier spindles. They were in such great shape when I disassembled the front end that I didn't look for '26 replacements. I would really be screwed if I had later spindles at 1.5 degrees camber.

Scott, so working with a set of rods and cones, the rods should all be in the same plane when viewed from the end of the axle, and should all be vertical and parallel when looking from the front. That's how I set the front axle in my last restoration, but it still needed some in-car tweaking with jack and chains to set the camber to specs. I guess the kingpins could still be parallel but both be canted to the side a little off vertical. Then the camber on one side wold be more than required, and the other less than required. We did have to 'adjust' both, more on one side and less on the other.

Allan from down under.

A Model T with steering in good shape and good alignment and true-running, balanced wheels and tires will handle safely and predictably at speeds of 50 MPH on secondary roads. Cross winds over 15 MPH and up to around 25 to 28 MPH will require some steering correction, but are not a serious problem. Most 2 lane secondary roads around here are in need of repair, with waves, dips, and troughs. A well-designed 2 lane roadway in good condition makes driving a real pleasure. (26-27 open car with Ford wire wheels)

After using heat and a press I was able to reduce the negative camber from 3.5 to 2 degrees. That was the limit of what I could do with my equipment. I decided to disassemble a spare front assembly. The distance between spring perches from what I removed and the spare is almost 1/4". I've never seen an axle drilled this far off. I will do a test fit on the car to see if this will be a problem. Wear in the perches and shackles is normal. I assume it's ok until proven wrong.

Mark, you may in fact have found two parts made different than each other, or you have just shown the result of a bent axle compared to a straight one. Impossible to tell without alignment rods.

Scott, you can see that the perch hole in the rusty axle is drilled off center.

I presume the perch holes and the king pin holes were drilled at the same time when the axle forgings were machined. Having the perch hole off centre as shown is not necessarily a problem if all the other holes are in alignment. It just means that that particular forging was mounted for machining a little bit off optimal position.
I could be wrong.
Allan from down under.

Is it drilled off center or is it worn from running a loose perch?

Rather doubt that perch hole was drilled off center, print shows parallel of both perch and spindle holes in the axle.

Pat, the hole is not worn. It took heat and my press to remove the perch. I inspected the hole and it was drilled off center. I will get dimensions today. I compared the kingpin to kingpin distance of these two axles and they are the same.

Mark, how is the other end perch hole. Is it off centre as well?
Anyone, is there factory information on how the axle forgings were machined?
Allan from down under.

I'd think they'd have used some kind of gang drill arrangement. Ford invested in a lot of specialized equipment. Maybe a bit broke or spun in the chuck, and this axle was rejected and diverted to a repair station where it was hand drilled or put in a drill press, then put back on the line or sold as a replacement part.

Allan wrote: ↑

Fri Sep 03, 2021 7:04 pm

Mark, how is the other end perch hole. Is it off centre as well?

Allan, yes but not as much. The black axle has perch holes 36 1/2" appart and the rusty one is 36 11/16". Kingpin spacing is the same between the two.

Edit: I mistakenly typed 36 11/32" rather than 36 11/16". The difference is 3/16".

TXGOAT2 wrote: ↑

Fri Sep 03, 2021 7:11 pm

I'd think they'd have used some kind of gang drill arrangement. Ford invested in a lot of specialized equipment. Maybe a bit broke or spun in the chuck, and this axle was rejected and diverted to a repair station where it was hand drilled or put in a drill press, then put back on the line or sold as a replacement part.

Yes, automated process to control drill hole locations on the axle for the perch and spindle holes. Tight tolerances. Holes were drilled rough then reamed to precision size. Would be very odd to have an axle drilled poorly. This is from 1915, so you know better machines were later in place.


If the bore of those perches holes are off that much, I wouldn't use that axle.


I have an 'un-drilled' axle forging, taken I think off the line for QA, as it has a square cut out section on the channel rib, guess for metal checks.

Nice and NOS, but no way to use it

Thanks Dan. I suspected as much. That is the best way to keep all the holes aligned and positioned relative to each other. So if one perch hole is out a bit, I figured the other may be as well. It just means that that particular forging may not have been mounted in the optimal position for the machining operation. It should not detract from its functionality. It would be interesting to see the relative positions of the king pin holes in the end yokes as well.
I did not expect the 5/32" variation in the spacing of the perch holes between the two axles, but it is not a lot in the scheme of things.
Allan from down under.

Allan, I mistyped my dimensions in an earlier post. I corrected that. The difference is 3/16", not 5/32".

I put the odd axle in the car and put weight on it. Everything looks like it will work OK. That axle has been used for many miles. It was repaired at some point with Steven's inserts and it is tight and straight. I plan to use it since the old one is unsafe. The old has 2 degrees negative camber on one end and 3.5 degrees on the other. That explains why I spent hours bending spindle arms to eliminate binding. I have other arms to use if I need them.

Mark, it is much easier and more controllable to adjust camber by bending the axle than trying to do the same on the short spindles. You do need to be able to tie the axle down when jacking it. Most body shops have that facility.

Allan from down under.

Allan, I bent spindle arms, not spindles. I was able to bend my axle from 3.5 to 2 degrees negative camber with a 20 ton press and heat. The bent end is too short to get good leverage to bend further with my tools.