I've replaced front kingpins and/or bottom trunnions on two Morris Minors, and both times I've noticed that the new trunnions have considerable end float in the horizontal swivel pin, even when bolted together tightly. See position of the feeler gauge in the attached photo - in this case it's about 0.8 mm.
This play causes a bad rattle in the front suspension, especially on small bumps. The castor angle means that the trunnion usually sits against the washer at the front end of the pin, but under braking or small bumps it moves back and forth. The rattle is quite obvious as a "clunk-clunk" when dabbing and releasing the brake pedal.
I note that in a very low mileage minor that I had for a while (which still had original suspension in very good condition), there seemed to be no play in these pins.
Question: Are the swivel pins supposed to have any end play? Were they factory fitted or matched to achieve this?
I could fix it by turning down the shoulder on the pin a bit to exactly match the length of the bush in the trunnion.... but I don't have a lathe. The easier option would be packing out the gap with some shim washers. I was thinking that a washer made of the right grade of industrial plastic might work, as it could be fractionally oversize so that it packed the gap tightly. I'd put it at the back end so that it wasn't taking the normal loading, although it would still be subjected to force under braking.
Anyone have any thoughts / knowledge / experience on this issue?
You can only get an accurate measurement of the clearance if the two trust washers are held tightly against the shoulders of the trunnion pin. Your photo does not show that. That upper nut needs to be done up tight before measuring.
I have just checked the for and aft clearance between a NOS bottom trunnion and NOS trunnion pin/thrust washers with the nuts done up (you have to use some packing between nut and thrust washer otherwise you will run out of thread) and there is no discernable play.
Only if the bottom trunnion is worn on the thrust faces will you experience fore and aft movement.
The thrust washers are hardened so the trunnion being forged steel and softer will wear first.
The only play required is that sufficient for the trunnion pin to turn freely in the trunnion. They were not matched at the factory.
There are two bushes in the trunnion and the overall length of the bushes should not be considered as they are slightly recessed into the trunnion and are below the trunnion thrust faces. You could end up with a trunnion pin that is then too short.
A shim in either plastic or steel should not be used in this application - it would not last very long.
I would suggest that you measure the distance between the trunnion pin shoulders and the distance between the thrust faces of the trunnion and report back on here with those measurements and further comment will be given.
As regards trunnion pin quality - I always recommend using the trunnion pins from the Morris Marina/Ital range as they are of a much better quality and will fit with no modification or additional work.
Phil
i have replacement pins in good original trunnions and have the same problem it's not enough to warrant a suspension strip but at some point i will have to face a bit of the pins to cure the play , i guess another case of a copy part copied wrong
I have in my collection 2 x brand new pins, 2 x old used pins, and 3 x old lower trunnions. Here are my measurements with calipers, probably accurate to 0.02 mm:
New Pins:
51.00
51.00
Old Pins:
50.30
49.98
Old Trunnions:
50.58
50.26
49.82
So quite a bit of variation. The trunnions are all a bit worn so they may have lost some width.
The red trunnion in the photo was the one which measured 49.82 so probably closer to 1 mm play with the new pins (I didn't actually measure it carefully before). Also, it seems that in some combos, the pins would be too short!
I'm not going to use any of these parts anyway, but I did notice that the (brand new) lower trunnions and pins which are now on the car had noticeable play when assembled (I never measured it, though) and they also have an annoying loud rattle. It seems unlikely that they were supposed to rattle like that from the factory, but I don't know!
I think 0.4 mm play would still be too big and would rattle... I'd like 0.1 mm or less. So it sounds like I'd need to get the pins turned down a bit to match the trunnions?
I would suggest that if you do not remove any metal from the trunnion pins until you have fully assembled and measured. There can be considerable differences between disassembled and assembled clearances.
You may find that the trunnion pins are surface hardened so you will not be able to machine any metal from the pin.
I would consider that 0.1mm or less to be an insufficient working clearance for this application when assembled.
My pins and trunnions were measured with a digital caliper which had been checked for accuracy against a Moore and Wright test piece.
So at 0.3 mm - 0.4 mm end play, do you notice any rattles?
I have a new set of kingpins and trunnions on order, and when I fit them, I'd like to eliminate the rattle.
I should say that they don't rattle on good roads, even on big bumps... it's only small sharp bumps like pot holes. But the last couple of miles to my house is a rough gravel road and it causes a lot of rattling!
I have never noticed any rattles when the trunnion and pins are fully assembled and correctly torqued.
Have you made sure that the rattle you hear is not from the front of the tie bar, the end of the steering rack, loose damper mounting bolts, the eye bolt pin or the swivel to trunnion clearance.
You may have to be selective of your trunnion pin length to get rid of any play.
Yeah I'm pretty sure I've eliminated everything else; there are new rubbers in the tie bars and the Armstrongs were recently reconditioned and are definitely well bolted down. I can't feel any play in the rack ends (ie jacking up and wiggling the wheels).
Just got the new kingpins and trunnions. With the nuts tightened lightly they have about 0.35 mm end play on both so I suppose that's specification. Would probably be slightly smaller once assembled and fully tightened.
Next time you drive, maybe you could try my test... i.e. with the car stopped and in 1st gear, right foot hard on the brake, gently let the clutch out a bit (without stalling). I hear a sharp "clunk" from both sides, and then another clunk when I put the clutch back in and the load comes off...
What you have described above I would not attribute to the miniscule amount of play between trunnion and trunnion thrust washers.
I would suggest that the problem could lie with the tie bar bushes.
The original BMC tie bar bushes had a raised centre boss of approx. 1.5mm height which fitted into the centre of the tie bar bracket hole and isolated the tie bar rod from the tie bar bracket.
The nut on the tie bar should be done up tight so that the front large washer butts up against the tie bar boss.
A common mistake is to tighten the nut on the tie bar until the bushes are just nipped which is wrong, they must be held tight.
A poly bush on the front for braking and a rubber bush on the rear for articulation.
Later after-market bushes do not have the centre boss and therefore the tie bar is not isolated from the tie bar bracket and subsequently knocks.
If as you say you have checked everything and there is no discernable play anywhere I have no further suggestions to make other than put it all back together and enjoy.
Thanks for the info... I hadn't got around to looking at it again due to trying to fix carb issues.
So I had a look at the tie rods. They were in fact pretty loose due to the rubbers being a bit old. I packed things out with a couple of washers to tighten them up (will need to order some more rubbers), and now they are nice and tight... but it made no difference at all to the rattles.
I am waiting with baited breath for a successful outcome to this issue.
The thing is, on my Traveller everything on the front suspension is brand new, but I am still getting the same clunk that you have on the drivers side. Normal roads are no problem, but pot holes or sunken drain covers or raised rumble lines when approaching roundabouts is a different story.
Please fix yours soon so I can have a look at getting mine sorted by the same method.
Sorry for the long overdue update to this issue, but I have finally got back to working on the front suspension. Hopefully the info will be useful.
I decided that it needed new kingpins and trunions anyway, so I have replaced them along with various other work. Here is what I did, and my findings. Note I had previously had the armstrong dampers rebuilt and made sure they were well tightened so I don't think they were the problem.
* Overhauled the steering rack: I basically used the best bits from three racks as the pinion and rack teeth were pretty worn in the middle of mine. I can see how this could cause rattles, but I don't think it was the problem. The rack end ball joints and spring loaded dampers on the old rack seemed to be fine (nothing obviously loose there).
* New polyerothane bushes throughout: The only really dubious ones I found were the inner end of bottom arm, but I don't think they were rattling as there was still rubber there and also they are always under pressure outwards, except when cornering. The front end of the tie bar would be a possible rattle source, but I had already replaced the bushes there and made sure it was nice and snug. Note I used rubber bushes rather than poly on the front end of the tie bar, because I think the poly ones are too stiff and threaten to cause the tie bar to flex instead (bad).
* New kingpins and trunions: The bottom trunion on one side was a bit loose, but I don't think it was rattling, as it is always under tension. HOWEVER, I discovered that both TOP trunions had quite a lot of play, especially when "rocked".
After putting everything back together, I have now eliminated pretty much all rattles from the suspension, and it also feels really nice to drive. So I think the noise was actually coming from the top trunions. I think that there is normally a small rearward force on the top trunion due to the castor angle; however, under braking or when the wheel passes over a sharp bump, this switches to a forward force due to the torque acting about the wheel hub. This caused the trunion to rock from one end of the availlable play to the other with a metallic clunk. I already had poly bushes in the top joint, so the rattle was transferring quite strongly through the dampers into the firewall.
I now think that Phil is quite correct in comments above - the factory end play of ~.2 to .3 mm in the horizontal pin on the lower trunion is not enough to make any rattle. The new trunions are the same in that respect.
I can see how such rattles are very difficult to diagnose: Basically, you have the steering rack and dampers bolted to the firewall quite close together, and the lower suspension arm and tie rod not far away. Anything that rattles is going to sound quite loud and many potential rattles will sound much the same!
For anyone trying to diagnose, I'd say start with the easiest things:
* Tie rod rubbers are tight and the tie rod isn't rattling around where it goes through the chassis. Nb: If it is, that's bad. I've seen them with notches worn in them, which could be quite dangerous.
* Damper bolts and steering rack bolts are tight
* Steering ball joints are not worn - inner and outer
* Rubbers at the top of the kingpin and inner end of bottom arm are good
* Trunion joints are not worn (top and bottom!) - unfortunately the suspension has to be dismantled to really check as there is always weight on the bottom trunion). Worn trunions are dangerous and should be replaced anyway, rattles or not.
* Steering rack is not too worn (especially the spring-loaded friction dampers at the ends, which should stop the rack from rattling inside the housing).
Hope this is useful info to anyone who finds this thread!
The original BMC rubber tie bar bushes had a raised centre that fitted inside the tie bar bracket and helped to keep the tie bar and bracket apart.
If you can find original NOS bushes they are the best rubber type to use.
As regards the fit and material of the bushes - it is best if a rubber bush is fitted to the rear of the bracket (helps articulation) and a poly bush is fitted to the front of the bracket (helps resist braking forces).
The problem with the bushes at the front of the tie bar is that with the tie bar being fixed at its rear end and which moves in an arc with the lower suspension arm - unfortunately with the way the tie bar moves it produces two different arcs of movement front and back and as they are not the same you have a conflict of forces which will wear the tie bar bushes more quickly than expected.
I have overcome the tie bar bush problem by adapting a Mini tie bar rose joint kit to fit the Minor tie bar which allows full articulation of the tie bar even though it is fixed at its rear end to the lower suspension arm. I would not recommend the rose joint kit for general use road use as it can put excessive loading on the tie bar bracket if not set up correctly.
It's not nearly as bad as it was, and sounds like it's only on the left side. I am sticking by my theory (above) that it's the top trunnion rocking on its thread as the wheel passes over small bumps.
I suspect dubious quality of the machining on the new trunions / uprights. I think the top left one only felt tight due to irregularities in the cutting, and as soon as it wore in a bit, it came loose again. However, I haven't dismantled yet. I plan to dismantle and check it all again soon anyway as I want to adjust the ride height and also it had a huge workout while participating in the Targa Rally late last year.
I use my Morrie for long trips, gravel roading, dirt motorkhanas and autocrosses (all on rough surfaces). I have also had a niggling rattle from both front corners, most noticeable when passing over cats eyes, road corrugations, etc. It started just 100mi after installing a brand new set of trunnions. No amount of greasing, disassembly, checking, measuring or levering revealed any play or looseness in any of the steering/suspension components. I have lived with the rattle until just last week, when I decided to jack up the car and smack the tyres with my most persuasive mallet.
When hitting the tyres front to back, then back to front, I was able to replicate the noise exactly. Upon closer inspection, I traced it to the above-mentioned lower trunnion pin which was 7 thou too long between the shoulders. I am currently in the process of machining these down. The goal is to have them 5 thou too short, then shim up from there. This should allow future adjustments to be made for wear on the lower trunnion faces. By having the shims firmly bolted between the pin and hardened outer washers, they should not be subject to wear in this (very) dirty area.
I would recommend that the Minor bottom trunnion pin is replaced with a bottom trunnion pin from a Marina or Ital.
The Marina/Ital bottom trunnion pin is of a much better quality and has a hardened surface.
Whist you cannot use a Marina/Ital bottom trunnion on a Minor you can use the bushes out of the trunnion, the thrust washers and the trunnion pin/thrust washer seals.
If the seals are in good condition and the trunnions well greased you should get nil dirt accessing the trunnion pin
I only use the Marina/Ital bottom trunnion pins for my Minor suspension.
Phil,
Do you have a source of just the Marina pins?
I have the same knock and have been chasing it for a long time to no avail. Exactly as mentioned above. I am really grateful for this thread.
Regards
Declan
Declan
The only Marina bottom trunnion pins I have been able to source are those that form part of a bottom trunnion repair kit.
There are quite a few repair kits on 'e' bay. I would go for the known brand ones or NOS if possible.
Phil
