TR3 Rack and Pinion Conversion, uneven lock.

[TRier]

Looking for some help here from people with long memories and histories with TR3s :-). I bought my 3 as a largely completed restoration, well I say largely completed, I'd probably correct that now based on recent experiences to "partially completed". 

The PO did a steering rack conversion, approximately back in 2011 but never tested it. The conversion raises a number of issues which I'll look into but the basic one I'd like some help on right now is the lock, the lock is uneven in that it locks probably a half a steering wheel turn less to one side than the other, the track rods are more or less even and neither of the wheels are coming up against any stop or restriction on the short lock side/rotation. Well no visible stop or restriction outside of the rack, its like the pinion simply comes to the end of the rack before the wheels are fully turned (in that direction). As if the pinion was inserted into the rack when the rack wasnt centered, it could well be as simple as that and perhaps one can just withdraw the pinion, centre the rack and then re insert it, I haven't tried yet and was just hoping that someone might advise me if thats feasible or not. I did read somewhere that back in the day there was a batch of steering rack conversions that did have this problem or one like it, the kit was purchased back then from the TR Shop not that they made the kit of course.

[stuart]

Sounds as if you need to remove the lower knuckle from the rack, centre the rack and then refit the knuckle. A lot rack conversions dont give quite as much from lock to lock as original anyway.

Stuart.

[TRier]

14 minutes ago, stuart said:

Sounds as if you need to remove the lower knuckle from the rack, centre the rack and then refit the knuckle. A lot rack conversions dont give quite as much from lock to lock as original anyway.

Stuart.

Thanks for the reply Stuart. So am I interpretting this correctly, it should be possible to remove the pinion (pinion and lower knuckle all one piece?) and then re insert it in the centre of the rack travel?

[BlueTR3A-5EKT]

 

Have you got lock stops on the trunnions.?  Are they restricting movements?

 

 

 

[TRier]

36 minutes ago, BlueTR3A-5EKT said:

 

Have you got lock stops on the trunnions.?  Are they restricting movements?

 

 

 

Hi Peter, no there is no contact whatsoever stopping the movement outside of the rack itself.

 

Niall

[RobH]

2 hours ago, TRier said:

As if the pinion was inserted into the rack when the rack wasnt centered, it could well be as simple as that and perhaps one can just withdraw the pinion, centre the rack and then re insert it,

Now maybe I am being a bit thick here  (quiet at the back !) but I really can't see how doing that will help.

Isn't this down to the position of the whole housing in the chassis?  The position of the pinion is fixed by the housing so that will achieve nothing more than would turning the steering wheel a bit.  

Disengaging the pinion and centreing the internal rack alone, without adjusting the track-rods, will just move the wheels from the straight ahead position,  so as soon as you straighten up it will be back where it was before and the steering wheel will be misaligned.  Surely you need to move the whole housing over a bit and then re-adjust the track-rods?

 

[TRier]

50 minutes ago, RobH said:

Now maybe I am being a bit thick here  (quiet at the back !) but I really can't see how doing that will help.

Isn't this down to the position of the whole housing in the chassis?  The position of the pinion is fixed by the housing so that will achieve nothing more than would turning the steering wheel a bit.  

Disengaging the pinion and centreing the internal rack alone, without adjusting the track-rods, will just move the wheels from the straight ahead position,  so as soon as you straighten up it will be back where it was before and the steering wheel will be misaligned.  Surely you need to move the whole housing over a bit and then re-adjust the track-rods?

 

Hi Rob, thanks for the input. I cant say I'm certain which is why I asked but no I dont agree that it would be the same as just moving the steering wheel. The flat gear internal to the rack will have a fixed distance it can travel, its driven over that distance by the pinion, if with the wheels in the straight ahead position the pinion is already 2,4, 6 teeth in the left direction on the flat gear then it will be able to move the racks internal flat gear less until it comes to the end of its travel. Whereas in  the right direction the pinion would be able to keep rotating for a greater rack distance (2,4.6 or whatever teeth) until it came to the end of the travel and the car would have a much greater lock clockwise, which it does. Thats how I visualise it anyway, I agree with you in that even if it is possible to centre the pinion on the rack/flat gear then one would still have to then adjust the track rods and remove the steering wheel and centre that, its a fruit of the poison tree situation. everything has been aligned now with only 70% travel on one side. I would say the process now (if its possible with the rack) is to disconnect the track rods, measure the full unimpeded  rack travel left to right, remove the pinion, move the rack's internal flat gear(using the track rods) so that its in the middle of the linear travel distance left to right then reinsert the pinion, the pinion rotation should then generate the same left to right travel. From that basic position re align the tracking etc. 

I dont know if its possible to remove the pinion, thats my query really, I've never done it before. looked at doing it once to disassemble for overhaul a Landcruiser rack but it couldnt be done without specialist OEM tools in that case. 

The rack position in the chassis is irrelevant, the flat gear/rack output is greater to one side than the other, thats incorrect no matter where the rack is in the chassis, yes moving it would improve the lock on the poor side but equally re position it on the "good" side to where the wheels started fouling the body, not to mind the impossibilty of coupling up the steering column rod in the new rack position.

 

Niall

[Lebro]

I'm with Rob on this one. if the track rod's are equal lengths, but the lock is uneven left to right, then the rack it's self is not central to the car.

If the rack cannot be moved left or right on it's mountings, then the solution is to make the track rods unequal in length until the lock is even on both sides ( with correct tracking of course), then re-position the steering wheel so it is where you want it.

Bob

[TRier]

1 hour ago, Lebro said:

I'm with Rob on this one. if the track rod's are equal lengths, but the lock is uneven left to right, then the rack it's self is not central to the car.

If the rack cannot be moved left or right on it's mountings, then the solution is to make the track rods unequal in length until the lock is even on both sides ( with correct tracking of course), then re-position the steering wheel so it is where you want it.

Bob

Hi Bob, thanks for helping but..... I dont think so. The rack is where it is in the chassis, the wheels are pointing more or less in the correct direction as is, making one track rod longer than the other without altering the tracking is by definition impossible and it would only change their positions relative to each other, it wont change the fact that both ends of the rack (the track rods, rod ends whatever) move further in one direction than the other, regardless of where they start from and relative to each other. With the current rack set up they will always each move further in one direction that the other. Moving the track rod ends would only impact the amount of lock if the limitation in travel was being imposed by wheel travel and as originally outlined there is nothing visible restricting movement external to the rack, not lock stops on the trunnions, no wheel foul, nothing outside of the rack is reaching any visible limit.

Edited July 25, 2023 by TRier

[RobH]

9 hours ago, TRier said:

making one track rod longer than the other without altering the tracking is by definition impossible and it would only change their positions relative to each other,

Sorry Niall but you are just plain wrong.  Shortening one track trod and lengthening the other by the same amount does not change the tracking, but what it does do is move the geared rack across within the rack housing.  That is the only way to correct the asymmetric lock If you cannot move the housing itself. 

 

 

 

Edited July 26, 2023 by RobH
typo

[TRier]

7 hours ago, RobH said:

Sorry Niall but you are just plain wrong.  Shortening one track trod and lengthening the other by the same amount does not change the tracking, but what it does do is move the geared rack across within the rack housing.  That is the only way to correct the assymetric lock If you cannot move the housing itself. 

Hi 

Hi Rob and thanks for the great sketch, I hope I’m wrong but will just have to make a few specific measurements and come back to you guys, I’ve been wrong plenty of times! Of course if I change both track rods it won’t change the tracking and it would as you have shown effectively re centre the pinion on the rack gear, however in this instance, the track rods are more or less even and the tracking looks more or less correct, so there would be one would imagine perhaps 1/4” adjustment both sides before one would start to say hold on something not right here. 1/2” which would leave each side a full inch different to to the other, one rod effectively at the end of its travel and the other close to or out of the rack would definitely be ridiculous, I haven’t measured the linear distance but the two locks are one full half turn of the steering wheel different!  So I just can’t see that much being made up with a tracking adjustment and if it could it would leave both sides at completely different extremes of their adjustments, something is really wrong here, I think.

I appreciate the help so I’ll make some measurements and take a few photos with the adjustments and come back to you. As a parting thought is there any chance that TR3s have left and right hand track rods of different lengths and they were supplied incorrectly back in the day with the kit when the conversion was done?

 

Niall

[Ralph Whitaker]

Some of the kits use Mini steering racks are were noted for the reduced turning circle. The better kits use TR7 racks which mine has, and there is no loss of turning circle.

Both track rods should ideally be the same length when the wheels are straight ahead otherwise you would get an uneven bump steer. Are both steering arms on the front uprights OK? and the track rod ends both the same distance from the brake disc. 

Have you removed the steering rack gaiters to take your measurements or are you measuring from the gaiter to the frack rod end.

Ralph

[RobH]

That is a very good point Ralph.  It may be that the rods are at present unequal, but if you measure from the end of the gaiter it looks correct.   The whole problem may just be incorrect track-rod adjustment.

 

 

 

Edited July 26, 2023 by RobH

[Trumpy3]

The problem here is we do not know where the rack came from nor its specifications. If I read it correct, the rack does not seem to be central to the car. To centralize the pinion is a simple task of turning the steering wheel until the pinion is central to the rack,ie same number of turns left to right. If the track rods are equal, the uprights are not being stopped by the inbuilt adjustable stops, no other hardware is preventing movement, then the rack is not central to the car. The front engine plate is the prime restriction to the freedom of selecting a suitable rack and could be the problem. Its not compatible and was located incorrectly.

WE tend to use the Mk2 Escort rack (fast and standard).

 

[Lebro]

+1

Bob

[TR NIALL]

Niall I may have a MK2 Escort Rack if you need,you know where to find me if needed.

[stuart]

I think your all going round in circles here so to speak. You need to centre the rack by going all the way from one lock to the other then halving the number of turns. You will then find your steering wheel is out. Take it off and find the correct point where it sits straight. Then remove the outer rod ends completely and take the gaiters off so you can have a look at the amount of thread showing on each inner rod end and check they are the same as some of the racks supplied years ago had too long inner rods which required threading further inboard and then the excess cutting off to allow proper tracking so it maybe this hasnt been done correctly. Also different outer rod ends are around that dont have the same amount of internal threading. Then you will know whats not correct.

Stuart.

[TRier]

47 minutes ago, stuart said:

I think your all going round in circles here so to speak. You need to centre the rack by going all the way from one lock to the other then halving the number of turns. You will then find your steering wheel is out. Take it off and find the correct point where it sits straight. Then remove the outer rod ends completely and take the gaiters off so you can have a look at the amount of thread showing on each inner rod end and check they are the same as some of the racks supplied years ago had too long inner rods which required threading further inboard and then the excess cutting off to allow proper tracking so it maybe this hasnt been done correctly. Also different outer rod ends are around that dont have the same amount of internal threading. Then you will know whats not correct.

Stuart.

Ok now we're getting to the nub of it. There were racks out there back in the day that had an internal issue that needed modification. That's what I feared here and if I were a betting man I'll bet is the case. Like I said I'll do the tests and measurements now and report back to everyone. 

Incidentally it does have awful bump steer too but that's another story for another day!

Thanks all for helping. 

[stuart]

44 minutes ago, TRier said:

Ok now we're getting to the nub of it. There were racks out there back in the day that had an internal issue that needed modification. That's what I feared here and if I were a betting man I'll bet is the case. Like I said I'll do the tests and measurements now and report back to everyone. 

Incidentally it does have awful bump steer too but that's another story for another day!

Thanks all for helping. 

I think theyre a TR7 rack which are the ones that need the inner rod ends cutting down. and rethreading further in. The bump steer is often actually caused by the location of the rack and also failure to swap the steering arms side to side to allow the outer rod end to be as close the the back of the front brake discs as possible.

Stuart.

[Lebro]

Also the height of the rack has an enormous effect on bump steer. A change of a few millimeters makes a surprising difference.

Bob

[TRier]

Thanks guys, I haven't really put any thought into it yet (there were too many other issues) but from the cursory look I did have I'm fairly sure that the height of the rack is far too high for optimal geometry. Probably a bigger issue to resolve and I want to keep the car on the road so I thought I'll sort the basic and most pressing problem first hence the lock query. Good to know you guys are out there for the bump steer too, right now I couldn't enjoy the full performance of the car on any kind of bumpy road that's for sure,  very twitchy might be an understatement.

Edited July 26, 2023 by TRier
Typo.

[TRier]

3 hours ago, TR NIALL said:

Niall I may have a MK2 Escort Rack if you need,you know where to find me if needed.

Thanks Niall,  generous as always.

[roy53]

5 hours ago, stuart said:

I think your all going round in circles here so to speak. You need to centre the rack by going all the way from one lock to the other then halving the number of turns. You will then find your steering wheel is out. Take it off and find the correct point where it sits straight. Then remove the outer rod ends completely and take the gaiters off so you can have a look at the amount of thread showing on each inner rod end and check they are the same as some of the racks supplied years ago had too long inner rods which required threading further inboard and then the excess cutting off to allow proper tracking so it maybe this hasnt been done correctly. Also different outer rod ends are around that dont have the same amount of internal threading. Then you will know whats not correct.

Stuart.

Almost word for word what i was typing at the time.

If they then measure the same and the track rod ends are the same it points to the steering arms which on some like the mini rack need to be swapped LH to RH .

These can bend so check measurements from the disc.

Roy

[Ralph Whitaker]

18 hours ago, stuart said:

I think theyre a TR7 rack which are the ones that need the inner rod ends cutting down. and rethreading further in. The bump steer is often actually caused by the location of the rack and also failure to swap the steering arms side to side to allow the outer rod end to be as close the the back of the front brake discs as possible.

Stuart.

Correct Stuart, I had to shorten and re thread the TR7 track rods by about 3 inches each side. I think I am right in saying Revington`s conversion uses a TR7 rack. As an aside, I wonder why the TR4 rack was not utilised in any conversion.

Ralph

[Drewmotty]

59 minutes ago, Ralph Whitaker said:

I wonder why the TR4 rack was not utilised in any conversion.

 

The critical dimension when choosing a donor rack is the dimension between the two inner ball joints where the track rods connect to the rack. The TR7 rack is only about 3mm out from ideal.