strip and rebuild a steering rack

[OnlyMe]

hi, i posted in the forum as there was no general forum. Sorry if its on thr wrong forum.

Q. Im after a guide on how to strip and rebuild a steering rack. I dont mind what car its for?

thanks

 

[71tr]

I recently did this for my TR6 and was very pleased with the outcome and the nondifficulty level. Review your Bently guide etc. for the exact procedure. Removing the lock nuts from the inner tie-rods can be a little cumbersome but once accomplished the unit disasembles easily. Really just a question of cleaning the unit, regreasing and reassembly with a couple of measurements to set tolerances.

 

[OnlyMe]

thanks mate, is a Bently guide an alternative to a haynes manual? Ive checked in a few of haynes manual and no info at all. It doesnt even mention who to remove it.

 

[Andrew Mace]

The Bentley manual is basically an exact reprint of the Factory Workshop Manual as well as the Owners Manual (and, I think, the Competition Preparation Manual?). Haynes are ok for many things, but little beats factory information.

 

[tdskip]

Any specific tips or techniques to share?

 

[71tr]

You know, I just did this a few months back and can't offer any particular tips. Just tear into it as the disassembly and reassembly are pretty intuitive.

 

[Alan_Myers]

Hi,

It really does make some difference which car the rack is out of.

I'll refer to Moss' online illustration for TR4/4A for item numbers, but you might need to look for different parts for your particular car.

Rebuilding my TR4's R&P about five years ago, I had trouble locating some parts. Other than that, the job wasn't difficult, but took some time and needs to be done right since it's an important safety issue.

At that time, I was able to get a new rack (#60), but not a new pinion (#43). One of the pinion bushings was NLA, too (#45 or 41).

The new ball joint sockets (#69) I bought were made of white nylon, rather than metal like the originals. I ended up re-using the originals, since they were in good shape.

TR4 through TR6 (I'm pretty sure), maybe others, have a bushing in the RH side of the rack tube (#58, LH steering/US spec car) that usually wears badly and nearly always needs to be pressed out and replaced. If worn, this is a major source of sloppy steering. I had no trouble replacing it myself.

There are some tab washers (#66) that lock the ball joint caps in place. I suggest always replacing these. Probably also a good idea to replace any and all springs (#54) that might have softened over the years, along with the plunger (#55)that rides on the rack, as a matter of course.

There is some adjustment, outlined in the factory manual, using shims (#52) under the top cap of the steering box.

While the rack is out is a good time to replace rack mounts, too, if needed. Depends on which car, but TR4A and later have rubber mounts (#98) that some prefer to replace with aluminum or urethane. My car has solid mounts, so no replacement was needed. If using the original rubber type, they need to be pre-loaded when the rack is reinstalled, refer to the manual.

It was a good learning experience. But honestly, considering time and parts I'd be tempted to just buy an already re-built rack assembly, if at all possible. (I couldn't find one for my TR4 at the time. I think TRF has them now.)

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[Paul Johnson]

You do not mention what type car. If the rack is power assisted, it will be a bit more tricky. There are some seals that must go over the rack that are very tight, but cannot be scored by the rack teeth. If you have one of those, cover the teeth with thin tape before installing the seals. Otherwise, it's about the same as a manual rack.

 

[DNK]

Is it possible to replace the parts needed to quicken up the ratio?

 

[Paul Johnson]

The steering ratio is a function of the number of teeth on the rack vs the number on the pinion. Not something one changes. It can, of course, be done, by having a machinist build you one or the other of the pieces. Many years ago, I needed a wheel bearing to fit a Cooper formula 500 car spindle, and a Sprite hub. Bearing company could build me the two I needed at $300 for the first one and $5 for the second.

 

[DNK]

They sell a quick fratio for the 6 and I was wondering if it was possible to sourse out the parts.

 

[SpannerMan]

[ QUOTE ]
It was a good learning experience. But honestly, considering time and parts I'd be tempted to just buy an already re-built rack assembly, if at all possible. (I couldn't find one for my TR4 at the time. I think TRF has them now.)

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[/ QUOTE ]

I tend to second that. I went through the rack on my TR6 when I first had it. I couldn't totally eliminate the slop between the rack and the rack housing at the far end from the pinion (passenger side). I put in a new bushing but too much wear on the rack itself - there was still transverse motion possible. Eventually I replaced with a rebuilt rack from Rimmer Bros. The funny thing about that one was that it was set up way too tight (binding)- the s-wheel wouldn't self center at all! Wear-in has helped, but not as much as adjusting the pinion plunger nut out (I have it wired rather than torqued/shimmed now). Most likely another rebuilt rack will be fine and you'll be very happy. Quick rack might be good to try, how about a smaller steering wheel to start? Pete

 

[OnlyMe]

when rebuilding the rack, does it have to be set to some setting? what setting is this?

 

[Alan_Myers]

[ QUOTE ]
when rebuilding the rack, does it have to be set to some setting? what setting is this?

[/ QUOTE ]

Hi,

There are a number of settings in the rack. The inner tie rod ends must be within a certain range of play. There is only so much allowable play in the bushings the pinion rides in. There is pinion end play to be adjusted with shims. And, as already mentioned, there is the bushing in the RH side (on a LHD car, it would be the opposite on a RHD car) that wears heavily itself and to the rack.

Finally, there is the tension between the rack and pinion themselves, which are adjusted by shims under the cap, that increase or decrease pressure from a plunger and spring arrangement inside. This is tested for accuaracy by how much weight it takes to turn the steering wheel. I would have to look it up in the service manual, but a test device is attached to the steering box and then weighted to see how much "effort" is required. Then, shims are removed or installed to adjust it.

All in all, I'd call it somewhat of an art, rebuilding a R&P unit. The more experience a rebuilder has with the process, the faster and better they will be at doing it.
The occasional home rebuilder is at a bit of a disadvantage.

This is especially true when some new parts are unavailable, you have to make do with used items. It can be tough to tell just by looking or "feeling" if something is reusable, or should be scrapped due to wear. It's not much fun assembling the best parts you can find, then testing it to see how it works, only to have to tear it all apart to swap something out.

Because of this, I still would generally recommend just buying a rebuilt R&P unit, hopefully complete with a warranty!

Some examples: The Roadster Factory offers rebuilt TR4A (actually TR4 from CT20063) through TR6, TR7, & Spitfire rebuilds. I think occasionally they have TR4 and GT6, as well. Their price range is aroung $250 on these rebuilds. ($200 for TR4A at Moss). Looks like Rimmer's price is $140, plus $170 core charge for standard ratio R& P for both the early TR4 and TR4A-TR6 versions. (Rimmer does offer a higher ratio version of the latter unit, for a bit over $200.)

I think you'd have a hard time gathering all the parts to do your own rebuild for less $ than the above.

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[OnlyMe]

thanks, what are the actual settings for any steering rack? just need it as a guide.

 

[Alan_Myers]

[ QUOTE ]
thanks, what are the actual settings for any steering rack? just need it as a guide.

[/ QUOTE ]

Here's what I can glean from the factory service manual for TR4/4A (which may or may not apply to other models):

- Pinion end float "use a dial gauge to determine shim pack that will gives minimum end play, yet allows free rotation". This appears to be checked without the rack installed.

- Pinion lateral movement in bushings - no comment in service manual. I can only assume a greased pinion should turn freely with no lateral play in either its upper or lower bushing.

- Pinion pressure pad (which holds the pinion against the rack) - Tighten to eliminate all end float, then add .004". Use a feeler gauge under the cap to determine shim pack thickness, then install shim pack and tighten cap. Check adjustment: When correct "a force of 2 lbs. at 8" radius will be required to rotate the pinion shaft".

Rack bushing - no comment in service manual. I have to assume a greased rack should move freely through the bushing without any noticible lateral play.

Inner tie rod ends - adjust shim pack to achieve ".002 inch ball lift".

In addition, an illustration in the service manual shows seven dimensions to check on TR4 and two to check on TR4A rack & pinion assemblies. I don't have any way to scan and post that illustration here. Perhaps someone else does. It's Figure 19, Section 2, Group 4 of TR4/4A Workshop Manual, Second Edition (Brooklands Books Ltd), Part No. 510322.