Play in the diff?

D

DAV8

Member
Hi All, Can anyone advise the best way to check the amount of play in the diff'? my car is a 1971 V8 auto, I have owned the car since 1975 and I am fairly certain that it is the original, it has covered approx 180,000 miles, my main reason for enquiring is:- the type 35 auto box sometimes will change down a bit rough giving the diff a bit of a thump, I suspect the box may need some attention before too long and perhaps the diff, I was thinking if I lift the rear of the car with the wheel clear of the ground and then hand turn the wheel to see how much play there is at that point? does this make sense? or I am happy to listen to any advise. Thanks in advance
DAV8
Dave
 
In my experience (of a manual 4-cyl P6 so feel free to ignore me...), every time I think a problem is developing in the drive train it turns out to be a drive shaft universal joint. I might just be allergic to the things but I seem to be replacing at least one a year. The last one cleared up a clonk similar to what you describe, and even substantially reduced a judder that I was sure was coming from the clutch.
 
DAV8 said:
I was thinking if I lift the rear of the car with the wheel clear of the ground and then hand turn the wheel to see how much play there is at that point? does this make sense? or I am happy to listen to any advise. Thanks in advance
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With both wheels on the ground see how much you can turn the prop backwards and forwards. That should show how much play there is in the diff, and if there is play in any of the driveshaft UJs. If you move the prop at the gearbox flange you'll be able to see any play in the prop UJs as well. Check the diff bearer plate and mountings, and the pinion mounting as well.
 
@harveyp6 - how much do you expect the propshaft to rotate with the wheels on the ground on a 4 cyl manual car? I've just come back from a trip to Sicily and noticed that if travelling at around 50 mph or more and releasing the accelerator, a vibration can be felt and heard. I did not have the opportunity to go above 60 mph and most of my driving was at 30 - 40 mph since I was participating in a Sicilian car club event around Ragusa. Here in Malta I rarely have the opportunity to go above 50 mph and when I do its for a split second and will have to brake to slow down. When cruising or accelerating she's a dream.
 
Hi All, Okay, I have checked the prop shaft as Harvey has described it and there is little or no play anywhere in either the shaft or the uj's, the diff bearer plate etc are all okay, with everything at working temperature (i.e. the gearbox oil is hot) the quality of the shifts is sometimes a bit rough especially the down shifts, the engagement into forward or reverse from neutral will give a bit of a clonk, oil level in the box okay (although this does leak quite a bit especially when it has been stood for a while, nothing unusual here) could the box need some attention?
DAV8 Dave
 
DAV8 said:
the quality of the shifts is sometimes a bit rough especially the down shifts, the engagement into forward or reverse from neutral will give a bit of a clonk, oil level in the box okay (although this does leak quite a bit especially when it has been stood for a while, nothing unusual here) could the box need some attention?
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It sounds like the kickdown cable might need adjustment. The symptoms you describe are often the result of the pressures in the box being too high, so if you also have slightly late upshifts that would also indicate that the outer cable needs adjusting upwards in the bracket to reduce the line pressure. Do it a little at a time, roadtesting in between adjustments.
 
Thanks Harvey, I'll have a look at that, I have been out for a run today (lovely weather) and the changes all seemed okay except for the delays in the forward to reverse and vice versa, sounds a bit like "sods law"
DAV8
Dave
 
Hi Harvey, Had a look at the kickdown cable and there is very little play if any at all, that is to say that when I operate the throttle shaft, the clevis holding the cable moves almost at once which seems to be okay, what do you think?
Regards
DAV8
Dave
 
DAV8 said:
Hi Harvey, Had a look at the kickdown cable and there is very little play if any at all, that is to say that when I operate the throttle shaft, the clevis holding the cable moves almost at once which seems to be okay, what do you think?
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The clevis may (and should) move instantly the throttle is opened, but that doesn't mean that the cable isn't too tight, which would give the symptoms you described. Try roadtesting, moving the cable adjuster upwards in the bracket one turn at a time and see if there is an improvement. The cable shouldn't be so tight so as to hold the valve in the box open, but not so loose that there is free play in the cable. Go too far, and have too much freeplay (slack) and you'll lose the kickdown function.
 
Hi Harvey, Managed to have another look at the cable today, just to be sure I'll run through what I've done, please correct me if I'm getting it wrong, looking down onto bracket there is the inner cable (kickdown cable) then there is a small hexagon nut and underneath the bracket is the outer cable with the adjusting nut about 2" below the bracket (I can't see any "locking nut" underneath the bracket) looking directly down on the adjuster I have turned the nut "anticlockwise" about half a turn, I was surprised how easy this turned, the bracket seems to be there just to hold the cable in place.
Regards DAV8
Dave.
 
If by "anticlockwise" you mean you are screwing the outer cable upwards into the bracket then that will reduce the pressures and that should soften the changes.
There isn't a locknut under the bracket, the outer cable screws into the bracket itself, and is locked by the nut on the top.

You need to roadtest as you go, noting the shift speeds, and providing they don't occur at too low a speed, you won't have gone too far. Check this by making sure the kickdown still works.
 
Hi Harvey, Yes, thanks again, that is what is happening, I will carry on with that and road test as I go, or as the weather permits.
Regards DAV8
Dave
 
Hi Harvey, I've managed to get a few road tests in despite the weather, the changes you advised have certainly done the trick, the changes are much better now both up and down, to clarify for anyone else reading this, the "anticlockwise" as I said is correct, to make sure I held a normal right hand threaded bolt with the thread facing down, turned the nut anticlockwise and the nut travels upward, similar, if you hold the bolt the other way up (thread upwards) and again turn the nut anticlockwise it travels upwards as required.
Many thanks for your help and advice, happy days!!
DAV8
Dave
 
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