Diagnosing the play acceleration drive line at low speed

[Andrew]

I am looking to drop the rear axle in the S3 to redo the leaf springs that are tired but I have another possible problem that should be addressed. I noticed when I was driving the car at low speed there seemed to be a lag in the drive train under load. Driving slow was irritating as to keep a load in the drive train to the back axle when moving forward axle seemed as if there was way too much play (not quite a clunk in the drive train but a lag). Is this the prop shaft, universal joint problem or a differential problem? Any ideas from anyone would be great or possible ways to diagnose the problem.

In the past I hear guys talking about taking the diff apart and replacing some bolts, is this the problem?

Any help would be great.

Andrew

 

[alpine_64]

Andrew, the bolts will be the ring gear bolts that the washer tabs squash and become loose.. They allow slack ans movement and wear out the diff.. The diff will whine badly and can get crunchy... You should remove and locktite them if you are pulling the diff... But doubt its the issue.

Id guess your uj's are worn.... Or potentially worn splines on wire wheels if you have.. But they will clunck.

 

[Mike O'D]

Andrew,

I just completed a refurbish of my S3 diff. I mentioned in another post that all 8 ring gear bolts were loose, and 1 was actually broken. The fit of the bolts to the ring gear carrier is pretty tight, so that probably isn't what you are feeling. I suppose if it was let go that way for some period of time, it could develop some slop though. The other thing I found was the lash between the pinion and ring gear was high. It's supposed to be .005" - .009" - mine was running above .012" This caused some extra movement, but again, not sure if you would feel it. My car was a non-runner when I got it (still is) so I don't know what it felt like before or if these fixes made any noticeable difference.

Mike

 

[Andrew]

I don't think there is a problem with the ring bolts but will be sure to check. Is it possible to just take each one out at a time, remove the washer/lock and then just use some red loctite and just torque each one down one at a time without taking everything apart. Then rebuilt with a new cover gasket.

This will be one of these new things that I have never done, so I am a little green here.

Thanks,
Andrew

 

[pruyter]

Hi Andrew,

Yes it is possible and also the best to do: one bolt at the time so that the crown wheel is not moving! I have done this job just some weeks ago.
And by all means use red Loctite and if I remember correctly it concerns Loctite 613.
Also very important is to use the right type of bolts, I used aerospace bolts with a W grade. The bolts must have a plain shank of 0.25 to 0.3 inch! The specified torque is 50 lbs. The bolts I used are NAS 1306-4. The o6 means 3/8 inch diameter and the -4 means 1/4 inch of plain shank.
Good luck with this job.

Regards,

Peter

 

[Andrew]

Hi Andrew,
I used aerospace bolts with a W grade. The bolts must have a plain shank of 0.25 to 0.3 inch! The specified torque is 50 lbs. The bolts I used are NAS 1306-4. The o6 means 3/8 inch diameter and the -4 means 1/4 inch of plain shank.
Peter

So you would not reuse the original bolts? I will have to see if I can source these aerospace bolts for the job but if the bolts are tight and everything looks good upon opening the Diff could I just service what is there? I know while you are there do the job right, right?

Thanks,
Andrew

 

[pruyter]

Hi Andrew,

I would not take any risk and change the bolts! The reason for the bolts going loose and break is that the tab washers are too soft,which is a design fault made by Rootes. So the remedy is that one re uses the old washers and don't use new ones, because the old washers are now flattened down so then it is easy to hold the torque. There are also people that don't use washers any more. I really recommend to use aerospace bolts and one thing more that I forgot to mention is that when you use the bolts I have used it is important to shorten this bolts with about 0.1 inch because they are a little bit too long and while the hole in which the bolt is placed is not long enough the danger exists that you don't get the right torque or that bolt breaks.
Obtaining the bolts costed me a long search on the internet and at last I found an adress in the UK which is for me, living in the Netherlands, quite convienent. I am sure that it is much easier to obtain this bolts in the USA.

Regards,

Peter

 

[jumpinjan]

I noticed when I was driving the car at low speed there seemed to be a lag in the drive train under load. Driving slow was irritating as to keep a load in the drive train...

That sounds like something is slipping or very worn. I would check everything from the flywheel to the wheel hubs.
Jan