Steering Rack Rebuild

[Sam280Z]

I have a 78 280z and have completely disassembled the steering rack (actually rebuilding 3 racks). I have attempted to obtain the parts required for a rebuild:

1) 2 angular contact bearings (15mm ID x 35mm OD x 12mm thick)

2) 1 oil seal (15mm ID x 28mm OD x 8mm thick TC5 style)

3) left and right rack bushings

4) left and right inner and outer tie-rod ends.

 

I ordered the above from Courtesy Nissan, but only the rack bushings and tie-rod ends were available.

 

I could only find angular contact bearings that were 11mm thick, so I turned 1mm spacers on my lathe out of stainless steel. This seems to work well.

 

The rack bushings that are available are evidently for a 240Z and the rack will not fit through them. I intend to machine some SAE 660 bronze bushings.

 

The oil seal is NLA from Nissan. I am attempting to source it now. Any suggestions on where to find this seal in small quantities? If I can only source a large quantity, is anyone else interested in them?

 

Would anyone be interested in spacers for the pinion bearings or rack bushings? If there is interest, I might put together a kit.

 

Has anyone successfully completed a rack rebuild? If so, any advise?

 

Sam

[zcarnut]

...The oil seal is NLA from Nissan. I am attempting to source it now. Any suggestions on where to find this seal in small quantities? If I can only source a large quantity, is anyone else interested in them?

 

Hello Sam;

 

I rebuilt my the rack in my 260Z (which is the same as the 280Z rack) about eight months ago. I was able to a new oil seal from Nissan. However, I was also rebuilding a manual 280ZX rack (very similar to the 260/280 one) at the same time and I noticed that the 280ZX oil seal would probably work in the earlier rack although it had a different part number (48125-78500). You can see if this seal is still available. The ZX seal does not need the seal retainer piece (it's the collar held in place with two 8mm bolts), but you may want to use it anyway.

 

...I could only find angular contact bearings that were 11mm thick, so I turned 1mm spacers on my lathe out of stainless steel. This seems to work well...

 

Yeah, these are special bearings made by Koyo just for Nissan (I even telephoned a Koyo engineer to confirm this). I just used a standard 11mm thick bearing with a Nissan valve spring shim. It’s 1.0mm thick and has the correct dimensions. Worked perfectly.

 

...The rack bushings that are available are evidently for a 240Z and the rack will not fit through them. I intend to machine some SAE 660 bronze bushings...

 

Yes, this is a good solution. I had my machinist make me two sets of bronze bushings for my racks.

 

 

The biggest problem I had was finding a pinion shaft. New ones are NLA so I disassembled several used racks (Thank you, Z Barn) until I found one with minimal wear. I thought about rotating the pinion shaft 180 degrees so that at the “straight ahead position” the pinion shaft would have a different sequence of gear teeth in contact with the rack. Most of the pinion wear occurs in the “straight ahead position.” However, the indexing groove on the pinion shaft would be in a different position and might cause a problem when the steering shaft is mated to the rack.

 

I would love to see someone make new pinion shafts. I wonder how the aftermarket re-builders solve this problem?

[Sam280Z]

Thanks Steve. This is excellent information. Especially the valve spring shim idea. How did you come up with that?

 

I do have a question about the 280ZX seal though.

Just by looking at the drawings in the microfiche, it appears that the 280ZX rack bearing preload is set with different thickness snap rings. The 280Z rack bearing preload is set with shims under the retainer. The 280ZX and 280Z racks both use the same part (48018-E8700 NLA) bearing. Since the bearing has to fit in the rack, the hole is slightly over 35mm. It appears from the drawing that the 280ZX rack seal rides in this same hole (no retainer). The 280Z seal rides in the retainer and has an OD of 28mm. From the drawings, it looks like the 280ZX seal would have to have an OD of 35mm. Am I interpreting the drawings correctly?

 

I guess I'm lucky with the pinion gears. None seem to have appreciable wear. They are shiny where they ride on the rack, but I can still see the tool marks from when they were originally made...

 

Thanks again for all your help...

 

Sam

[zcarnut]

...Since the bearing has to fit in the rack, the hole is slightly over 35mm. It appears from the drawing that the 280ZX rack seal rides in this same hole (no retainer). The 280Z seal rides in the retainer and has an OD of 28mm. From the drawings, it looks like the 280ZX seal would have to have an OD of 35mm. Am I interpreting the drawings correctly?

 

Yes, the ZX seal fits into a 35mm opening but it has a thin lip on one end that has an OD of 43mm. This lip positions the seal.

 

...The 280ZX and 280Z racks both use the same part (48018-E8700 NLA) bearing...

 

I think you’re mis-interpreting the bearing numbers in the fiche, Sam.

 

48018-E8700 is the bearing used in the ZX rack (and also the 240Z rack) and it is a “standard” bearing, readily available at your local bearing retailer.

 

48018-N3400 is the special bearing (NLA) used in the 280/260Z rack.

 

Also,

 

48125-N3400 is the 280Z seal, and 48125-78500 is the ZX seal.

[Sam280Z]

Thanks again. You are right, I had misread the fiche.

I don't think the 280ZX seal will fit if it is 35mm OD unless I machine out the bearing retainer and find some way to preload the bearing.

 

Did you have to modify your valve spring shim to fit in the rack? I pulled a shim from a box of parts I have and it is considerably larger than 35mm. The valve spring itself is nearly 35mm. I'm wondering if I got a head that had been reworked with aftermarket shims or something?

 

Thanks again,

Sam

[ecp48]

There is a thread on the IZCC site on rebuilding the 280Z rack. The writer, John Downing, talks about honing the bushing to a snug/interference fit with a brake hone. The idea being the rack wears at the point of contact with the bushing and has created through wear a smaller outer diameter at that point than at the ends (due to lack of point lubrication, no zerk fitting, like the 240 has). It is my understanding that this is the reason, the book says the 260/280 rack must be professionally rebuilt.

 

If you are going to machine the bronze bushings, better check the diameter of the rack at the ends and at the wear area (normally centered and and every .5 inch for several inches each direction probably 4 inches total.

[Sam280Z]

I found the zhome article: http://zhome.com/ZCMnL/tech/StrRack.htm

 

I'm not sure if the rack bushings are supposed to be enlarged. I'm pretty sure they are for a 240 which supposedly has a smaller diameter rack. The 280Z microfiche shows the bushings on the exploded diagram, but they are not called out on the diagram with a key number (http://carfiche.com/fiche009/s30/?6:b:11).

 

The bushings consist of a steel shell with a copper lining. A hone (stone) will not do a good job of enlarging them (the stone will fill with copper and stop cutting. Sand paper wrapped around it would work, but there appears to be quite a bit of material to remove). An adjustable ream would work if there is enough thickness of the copper before you get into the steel. I will check this out and post what I find. I could turn a holder that is the same ID as the rack housing and press the bushing in and turn the inside on my lathe. Again, the issue is having enough copper bearing material thickness.

 

I see very little wear on the rack itself. I can still see the tool marks from where it was machined, but I will machine the new bushings to be the tightest sliding fit I can manage...

 

I still have not sourced an oil seal.

Also, could someone measure the outside dimension of a valve-spring shim and see if it is 35mm?

 

Thanks,

Sam

[zcarnut]

...I still have not sourced an oil seal...

 

Sam;

 

How about trying a 15mm x 28mm x 7mm CR seal? (Available from SKF.)

 

[Sam280Z]

It looks like that I will have to do that. The TC5 style seal is just not available. I did find out that is is relatively cheap to get a seal made (on the order of $1.00 per seal). But you have to get a lot made.

 

I will look into getting a standard bearing.

 

For a bunch of info on seals, I found this:

http://www.rlhudson.com/Shaft%20Seal%20Book/index.html

 

Thanks,

Sam

[Sam280Z]

Worked on it again this weekend.

The rack bushings from Nissan have plenty of material to machine them out. I made a holder that is the same ID of the rack, pressed the bushing in, turned them on my lathe until they were a nice fit on the rack. It did take a little cleanup with 320 grit sandpaper wrapped around a piece of foam sponge and spun with a hand held drill.

 

I re-used the original seals. After cleaning them up, they looked brand new.

 

One rack is worn out. This can be determined by engaging the pinion with the rack and trying to rock the pinion. all of the rack is real tight - the pinion doesn't rock - except for the part where the pinion rides when the wheels are straight ahead.

 

Sam

[iflyfast1]

Sam

I've been watching this thread with a lot of interest. My biggest complaint with my Z right now is the sloppy steering. I didn't address it when I was rebuilding the suspension because I figured I would change the rack out for a WRX unit. It doesn't look like anybody has come up with a good solution though especially for the guys running an LS1.

 

Are you still looking at possibly putting together a kit? I would be interested. Also, if your still looking at a group buy for the seals, count me in.

[Sam280Z]

I managed to re-use the seal. I cleaned it up and saw no problems.

 

Your sloppy steering is either from the rack bushings, pinion/rack wear, inner tierod end wear, and/or outer tierod end wear. Ball joints and strut bearings may also contribute. You said that you had rebuilt the suspension. Did you replace everything but the rack components? You should be able to take the rack out and judge the wear w/o disassmbly by trying to rock the various components.

 

I don't see a kit as viable right now.

 

Sam

[iflyfast1]

I have replaced everything that can wear except the inner tie rod ends (poly bushings, wheel bearings, ball joints, outer tie rods, shocks, springs, brakes etc., etc., etc.). I didn't touch the steering rack at all since I had hoped to replace the rack with a new WRX unit. I was told when I got an alignment that the inner tie rods are worn. I think I'll just buy the inner tie rod ends and 240Z rack bushings. I'll have the bushings turned down at a local machine shop. I'm hoping the rest of the rack is in good shape since the car had pretty low miles when I bought it. If not, I may just replace it with a 240Z rack since parts are still available. Good information on this post though.

[Sam280Z]

The rack bushings are split. You will need to have the machine shop bore a piece of stock to the same size as the rack housing ID. Then press in the bushing. Have them bore it to 25mm (that is the rack diameter). You can then use 320 sandpaper wrapped around foam sponge to take off just enough for the rack to slide through easily. Use a bolt and nut as a mandrel for the foam and spin it with a hand drill.