Steering Rack In/Out Play

[Rupunzell]

I agree with each of these points. The pinch bolt maybe if worn or forced enough might be able to be off but I remember it sliding home easily enough when I matched up the splines correctly.

The only thing I could see causing the pinion movement other than the rack itself at fault would be the rack mount bolts loose or firewall flex but I checked the bolts and certainly not enough force to flex the sheet metal.

The pinch bolts on the steering wheel axle to steering rack pinion will not engage the nut if the splined ends are not properly fitted. The splined shafts are grooved for the M8 bolt, long as stock length bolt and prevailing torque lock nut is used, improper assembly is not possible by design.

loose steering brakes are possible, but not common at all. There is a set of bushings used between the steering rack to bracket. These seldom create problems, and the hardware involved self loosening is not common.

~Check this.

Removal of the steering rack is not that difficult, regardless do all the previously mentioned checks to completely rule out those common issues.
Proper steering on the exxe should be like a good micrometer, tight, precise, direct and about zero slop.


Bernice

 

[Rupunzell]

View attachment 74976View attachment 74977
The gray TRW unit is the one I removed due to a vibration issue but a total overhaul so I honestly cannot remember what fixed it. The black installed unit is the MWB rebuild. This looks to be inverse of Mike's experience.

Not common to have a problem with the steering rack gears, they hold up pretty good.
~The pinion gear is held on with a threaded adjuster and staked in.. If you try to simply un-screw the pinion gear retaining nut the threads will be destroyed and you'll never get it back together again.. Proper way to deal with this is to cut out the staked areas on the threads on a milling machine before removal. If you do not have access to milling machine or help from a machine shop. Stop.. do not proceed.

The plate with the two M6 screws hold the spring and tensioner and shims for setting up the rack to pinion pre-load..

Not a lot to "rebuild" in these steering racks as the gears are very durable long as they are properly lubricated (early versions are gear oil, later versions are moly grease).

The pinion bearing holds up good. As previous mentioned, the most common problem is the plastic bushing on the end of the steering rack gear tube inside the cover boot.

Bernice

 

[Yves]

Three are a few places where excessive play in the steering can happen.

Most common is the plastic bushing for the rack gear inside the steering rack has come undone or died (most common failure, the three plastic tabs bust off). Idea replacement is to make a bushing from SAE bearing bronze or replace it with the stock FIAT plastic part. Making this bushing out of aluminum per the PBS "race" book is not good as aluminum is a horrid bearing material unless properly alloyed to be a bearing material.

Check the ball joints at the ends of the steering rack gear.

Check the ball joints at the end of the steering rack that connects to the front upright's steering arm.

Check the front wheel bearings for slop.

Check the lower ball joint for excessive slop (unlikely).

There is a needle bearing U-joint drive shaft between the steering column to steering rack's piñon gear, these can and do wear out.. and the splines on both ends must be proper and the M8 bolts clamping then together must be properly seated.


Bernice

Well come back Bernice we all miss you

 

[AKimball92]

I removed the rack looked it over. I was unable to "pull or push" the pinion in and out on the bench. However pushing and pulling the rack left to right definitely changed pinion location. I took measurements and saw a delta of 2.4mm stickout from far left to far right. You can see the witness marks in the pain here as well. Then looking closer i realized i can see threads for the larger diameter circle. I think the steaking didnt work on this rack and the whole top pinion cover is backing out. See photo #2. You can also tell the paint marker do not line up either from threaded cover to casted housing.

I think I could torque the down again. Close up that 2.4mm slip and either steak it back down or maybe fabricate a locking key similar to the rear engine cross member. The would allow for easy rebuild later.

 

[Ics19]

I think I could torque the down again.

Ouch - that would explain the movement While there may not be damage to the pinion / rack teeth, it might be worth a call to the vendor as it's had relatively low usage. You need to verify the thread of the ring nut and housing are undamaged too, as otherwise it may just come loose again if it's re-tightened.

In this thread https://xwebforums.com/forum/index.php?threads/steering-rack-part-3.15092/ @Rupunzell looks to have locked the ring nut with a screw that fits in a machined flat across the housing/nut - it would seem a much improved method than staking. Unfortunately the images have disappeared, but here's a snip from the archives:

Here's the part from the workshop manual if you do need to adjust yourself:

 

[Dr.Jeff]

I agree Andrew, if that nut has backed out it could explain what is going on. Although I would not necessarily be concerned about the "paint marks" for the position of the nut. Those marks were likely the ones from the factory when it was new, while a rebuilt unit would result in the nut being located differently when torqued. And the rebuilder may not have placed new paint marks on it. I'd check the torque of the nut as it sits to see if it has indeed backed out as you described.

 

[Ics19]

Those marks were likely the ones from the factory when it was new

I think the rack has been spray painted black as they're plain alloy from the factory - so likely from the rebuild?

 

[Rupunzell]

This is the steering rack in the 74' (needs a good home). taken apart, upgraded then put back together with modified solid mounts. The milled flats on the steering rack match the mounting flats on the mounting blocks to stop any rotation of the steering rack and positively locates the steering rack. The mounting blocks have been doweled pinned to locate the mounting holes and stop any mounting block movement.

Elimination of the rubber mounts improves steering feel and makes an absolute solid connection to the chassis. Aircraft spec hardware replaces all stock ISO metric hardware.
Yes, after the preload on the pinion bearing has been set, a flat was milled in place then a screw hole drilled/tapped for a screw (with loctite)

to hold it all in place instead of staking. This allows future take-apart without dealing with the staked pinion nut problem.

 

[Rupunzell]

Steering rack in the 74' (needs a home)

The plastic bushing, replaced with a bearing bronze bushing. This is the most common problem in these steering racks. The replacement bushing is a press fit into the housing. There can be no slop between the bearing and bushing or the steering will not be precise and the bushing must have some means of positive retention like roll pins or small screws or etc...

 

[Rupunzell]

I removed the rack looked it over. I was unable to "pull or push" the pinion in and out on the bench. However pushing and pulling the rack left to right definitely changed pinion location. I took measurements and saw a delta of 2.4mm stickout from far left to far right. You can see the witness marks in the pain here as well. Then looking closer i realized i can see threads for the larger diameter circle. I think the steaking didnt work on this rack and the whole top pinion cover is backing out. See photo #2. You can also tell the paint marker do not line up either from threaded cover to casted housing.

I think I could torque the down again. Close up that 2.4mm slip and either steak it back down or maybe fabricate a locking key similar to the rear engine cross member. The would allow for easy rebuild later.

If the pinion retaining nut has come loose, tighten the nut back to its original position using the stake marks as reference points. A loose pinion retaining nut would cause improper lash or gap between the pinion to rack gear..

Ideal way to prevent rotation of the pinion lock nut is to mill a flat spot once the pinion nut has been properly set, then drill-tap a hole to add a screw with washer to hold and locate the pinion nut in place.

 

[AKimball92]

I agree Andrew, if that nut has backed out it could explain what is going on. Although I would not necessarily be concerned about the "paint marks" for the position of the nut. Those marks were likely the ones from the factory when it was new, while a rebuilt unit would result in the nut being located differently when torqued. And the rebuilder may not have placed new paint marks on it. I'd check the torque of the nut as it sits to see if it has indeed backed out as you described.

I added the paint marks when I installed it to find center, at least center + the correct rotations on both sides. The blue line went from pinion all the way to housing.

I think the rack has been spray painted black as they're plain alloy from the factory - so likely from the rebuild?

I believe MWB paints them black when they clean and overhaul the racks.

 

[AKimball92]

Steering rack in the 74' (needs a home)

The plastic bushing, replaced with a bearing bronze bushing. This is the most common problem in these steering racks. The replacement bushing is a press fit into the housing. There can be no slop between the bearing and bushing or the steering will not be precise and the bushing must have some means of positive retention like roll pins or small screws or etc...

View attachment 75088

Hey Bernice, Thats a mighty fine looking steering rack. It looks like you milled out the threads to the pinion & housing. How do you set the bearing preload? purely with a press? Is the screw enough to keep it from backing out.

This is the steering rack in the 74' (needs a good home). taken apart, upgraded then put back together with modified solid mounts. The milled flats on the steering rack match the mounting flats on the mounting blocks to stop any rotation of the steering rack and positively locates the steering rack. The mounting blocks have been doweled pinned to locate the mounting holes and stop any mounting block movement.View attachment 75087

Yes, after the preload on the pinion bearing has been set, a flat was milled in place then a screw hole drilled/tapped for a screw (with loctite)View attachment 75084View attachment 75085 to hold it all in place instead of staking. This allows future take-apart without dealing with the staked pinion nut problem.

I have wanted to to do the bronze bushing upgrade and plan to in the future. Currently this one has no issues with that yet. My neighbor does have a small CNC lathe he is getting up and running. This would be the perfect starter project if I supply the stock.

Thanks for offering it but unfortunately I am not in the position to buy unnecessary parts at this time. I was laid off last week and currently job shopping in the Metro Detroit area. .

 

[Rupunzell]

Hey Bernice, Thats a mighty fine looking steering rack. It looks like you milled out the threads to the pinion & housing. How do you set the bearing preload? purely with a press? Is the screw enough to keep it from backing out.

Pinion bearing pre-load per spec in the FIAT service manual. Two details, the retaining nut is related to the pinion bearing, the shims on the other side are related to gear lash set up and pre-load. Don't lose the set up shims under that sheet metal cover if this is taken apart.

Yes, adding the 8-32 button head screw stops the pinion nut from backing out by the screw clamping down on the flat milled surface. The pinion nut would need to push the screw out to loosen.. This would require several hundred pounds which is not possible unless something went explode with the pinion gear to rack gear assembly. This only works if the seating surface for the retaining screw is machined flat and the screw thread are equally perpendicular to that milled surface. Loctite is a must for that retaining screw.

Moly grease (Redline CV-2) works good as a lubricant. Early steering racks were oil filled, later the switch over to moly grease was made as OEM.


Bernice