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Tdci castor angle - possible difference?


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Hey all,

I have come across a difference in the front ends of Tdci to at least the Tdi Defenders. There is a larger clearance between the track rod and bottom of radius arms on the Tdci versions.

I have checked and the radius arms are the same depth at the point where the TR passes under them. 
 

So I’m wondering if there was either a pinion or castor change (or both). I was thinking maybe pinion change due to the different drive line angles of the Tdci. 
 

The difference is approximately 8-10mm which would equate to at least a 2.5 degree castor change (more) 

 

thoughts?

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12 hours ago, miketomcat said:

At somepoint they started fitting swivel pin housing's that were both LHD and RHD, so it's possible the casting/swivel pin locations got altered at the same time.

Mike

 

Possible for sure. I’d love to know the castor and pinion angles of a stock Tdci.  That would provide more information. 
 

Given that LR were stripping out by way of cost cutting many bits on the Tdci, I’d be surprised if they made whole new castings for the swivel housings (maybe it was just a change in machining, but why would the keep the castor, pinion and housing the same and just clock the swivel housing?) 

Having the RA brackets clocked around a few degrees would not cost much other than the initial change to design cad and this would provide a pinion angle change, and as a by product, castor change.

 

a lot of guessing though…

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My Thoughts: - I find it hard to believe that LR would do something like change the castor angle - its not unheard of - but its just a weird quite fundamental thing to change.

Have you looked at the ball joints? I've never really thought about it but do their dimensions change much?

Also - what era is the Tdi you're talking about? - as from ~94 onwards LR started fitting the taper roller baring type swivel pin/housings compared to the Raliko bearing type - there is quite a difference in design of swivel housings between the two... I could see it being a slight different position between the two.

As far as I am aware LR carried on using the same swivel housings right from the start of the 300tdi era vehicle's to the end of tdci production.

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45 minutes ago, Maverik said:

My Thoughts: - I find it hard to believe that LR would do something like change the castor angle - its not unheard of - but its just a weird quite fundamental thing to change.

Have you looked at the ball joints? I've never really thought about it but do their dimensions change much?

Also - what era is the Tdi you're talking about? - as from ~94 onwards LR started fitting the taper roller baring type swivel pin/housings compared to the Raliko bearing type - there is quite a difference in design of swivel housings between the two... I could see it being a slight different position between the two.

As far as I am aware LR carried on using the same swivel housings right from the start of the 300tdi era vehicle's to the end of tdci production.


I have compared my 1998 Tdi Defender and Disco 1 96-98? Swivels, both TRB of course. I have been given TR to RA clearance measurements from two more 300Tdi Defenders. All are the same.

I noted the difference visually (no tape measure unfortunately) on three separate Tdci’s (130 & 2x 90s) whilst looking at a display at the local LR dealer. 
 

I had that confirmed by a Tdci owner with measurements. 
 

Conditions were - must have stock radius arms, no slotted swivels or offset bushes. On flat ground, steering in the straight ahead position and no articulation.

 

There is definitely something going on. Castor change may just be a byproduct of pinion rotation….

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13 minutes ago, uninformed said:


I have compared my 1998 Tdi Defender and Disco 1 96-98? Swivels, both TRB of course. I have been given TR to RA clearance measurements from two more 300Tdi Defenders. All are the same.

I noted the difference visually (no tape measure unfortunately) on three separate Tdci’s (130 & 2x 90s) whilst looking at a display at the local LR dealer. 
 

I had that confirmed by a Tdci owner with measurements. 
 

Conditions were - must have stock radius arms, no slotted swivels or offset bushes. On flat ground, steering in the straight ahead position and no articulation.

 

There is definitely something going on. Castor change may just be a byproduct of pinion rotation….

I guess you should look at diff input angle from horizontal or some similarly defined datum - that sounds the most likely reason as you've outlined then compare old stuff to the tdci.

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The rules used to be that you kept the same part number if the part was interchangeable both new for old and old for new, but if not, you had to use a different part number, otherwise stock control is impossible. So by comparing part numbers you could see if a part had changed, though sometimes they seem to change numbers for the hell of it, and sometimes don't bother when they should so it isn't 100%. But it may give a clue.

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The axle tubes, radius arms, swivel housings and so on are all the same dimensions (ignoring the change in thickness of radius arms).

The actual castor angle will vary with spring length, so use of RR/Discovery springs on a 110 with a winch would change the ride height and thus the castor angle as the castor angle rotates around the rear end of the radius arms.  They are all nominally three degrees, but realistically, I’d expect a Discovery or RR to have a slightly greater castor angle than a correctly sitting Defender, and vehicles given cheap lifts will lose a considerable amount of castor, which is why proper lift kits come with revised arms or at least with corrective bushes.  Even fitting softer or harder standard spring would alter ride height and thus castor under the vehicle’s weight.

There are many reasons you may see a different void between the track rod and the radius arms.  Unintentional variations in the siting of the axle brackets, the use of castor correction bushes, worn bushes and variations of the height of different brands of steering rod ends are all obvious examples, in addition to the possibility of changes to the outer swivel casing details such as arm angles or depth of reaming of their steering rod end taper holes.

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10 hours ago, cackshifter said:

The rules used to be that you kept the same part number if the part was interchangeable both new for old and old for new, but if not, you had to use a different part number, otherwise stock control is impossible. So by comparing part numbers you could see if a part had changed, though sometimes they seem to change numbers for the hell of it, and sometimes don't bother when they should so it isn't 100%. But it may give a clue.

Yes when I get a chance I’ll do some part number trolling, but as you say, number superseding and random changes could be a problem. 
 

I would suspect a possible number change regarding swivel housing (maybe) when they went from Tdi to Td5 with ABS as the ABS sensor passes down through the top swivel pin. Whether it’s just a change in the pin, swivel ball , housing or all 3 I don’t know….

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4 hours ago, Snagger said:

The axle tubes, radius arms, swivel housings and so on are all the same dimensions (ignoring the change in thickness of radius arms).

The actual castor angle will vary with spring length, so use of RR/Discovery springs on a 110 with a winch would change the ride height and thus the castor angle as the castor angle rotates around the rear end of the radius arms.  They are all nominally three degrees, but realistically, I’d expect a Discovery or RR to have a slightly greater castor angle than a correctly sitting Defender, and vehicles given cheap lifts will lose a considerable amount of castor, which is why proper lift kits come with revised arms or at least with corrective bushes.  Even fitting softer or harder standard spring would alter ride height and thus castor under the vehicle’s weight.

There are many reasons you may see a different void between the track rod and the radius arms.  Unintentional variations in the siting of the axle brackets, the use of castor correction bushes, worn bushes and variations of the height of different brands of steering rod ends are all obvious examples, in addition to the possibility of changes to the outer swivel casing details such as arm angles or depth of reaming of their steering rod end taper holes.

I figured the relationship between spring height and castor change was a given…. But there are factory specs and I thought maybe someone new the specs for the Tdci. 

The 3 as new Tdci at the dealer, all in stock form, showed the same gap between TR and RA regardless  of the bump stop gap/spring height. (130 being approximately 100mm and the 90s being closer to 75mm)

The fully restored RRC definitely had a closer gap, (by the ~10mm) as with the restored 1997 camel trophy 110.

 

As I stated, I have, and  are trying to eliminate the variables. Track rod dia has been accounted for with data collection. Again I have specified stock radius arms, no offset bushes or slotted/rotated swivel balls.

 

For the RA bushes to be worn out enough for the TR to RA gap to reduce  by ~10mm on a Tdi, the vehicle would be undriveable.  And across multiple vehicles seems unlikely…..

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Then I’d imagine the tolerances of bracket positions on the axle case and variations in the internal taper diameter of the swivel arm bores and the different suppliers of rod ends to be the main causes.  LR tolerances are huge, and I have seen very different lengths of tapered stud and depth of socket between brands of rod end, significantly changing the position of the rod.

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