pinion nut

[chicagojeff]

Hi All,
So I am in the process of replacing the pinion seal in the diff of my 1967 S3, the diff is out of the car, and of course I removed the pinion nut without first noting with ink where it was lined up. But, as the attached picture shows, there's a groove in the nut and in the shaft that makes me think that the groove was made to show where things line up? If so, it would mean that I can avoid all the mumbo jumbo with respect to backlash, mesh, preload...or no? Any thoughts welcome. Best, Chicago Jeff

[mbell]

The nut it's staked to hold it in position. So that impression will line up with the removed thread section.

The question is can you get the correct number of rotations? From doing this I think there is a chance you could. That wouldn't guarantee the back lash is correct and the diff will run well.

So question of if your ok with risk of having to remove diff again and get it set later if it's not good. Or just want to get that done now...

[Craven]

Best bet do the nut up to 30 – 35 lbs/ft, but read up on here about oil leak pass the nut.

[chicagojeff]

Thanks guys. I am thinking that if that staked spot is correct from before, then I should be able to feel it to get it right, given that the torque will be in the 30-35lb range. In other words, a whole rotation of the nut either tighter or looser should be pretty easy to feel on the resistance from the bearings. But of course, it's all out now and as we all know it's a small pain to remove the diff, and a huge pain to take apart the rear end--which is splattered all over the garage floor. (This car is a one-owner car I am restoring. Has about 35K on it, and hadn't been driven since 1972.)

Is there any reason to think that the backlash and preload would change? Maybe if bearings were worn out.

I guess a related question is, if you were going to do this all correctly, what's the difficulty on a scale of 1 to 10?
In other words, how hard is it and what tools are actually required for setting correct backlash and preload? I have the manual, Buckland's book, and have read all the posts on this, but still hard to judge even which tools to buy. Good luck finding the Ford tools in the manual!

Thanks again. I will write a blog about all of this when done.

[2cams70]

Ideally you should recheck the pinion bearing preload as well as replace the nut and the collapsible spacer but given this diff is out of a low mileage car you should be OK to just line up the nut in the position it was originally. I would not tighten the nut itself to any torque figure. That is not the correct way to set the bearing preload.
In your case I would gently tighten the nut just until there is no more end float of the flange on the pinion shaft itself. I'd then continue turning the nut until the stake mark is in the correct position, restake and leave it at that. Unfortunately I think it would be on the 10 scale of difficulty for you to fully set up a diff given the types of questions you are asking. You need to do some more reading and researching yourself about diff setup generally. The process is generally similar no matter what the vehicle.

Also may I suggest a change of mindset when it comes to these old cars. An occasional drop or two of oil from a non-critical area - eg. pinion shaft seal, gearbox extension housing seal, cam cover gasket is nothing to concern yourself about. There are far, far more serious things that can and will go wrong!

[Craven]

No one is advising a pinion preload can be set by a nut torque figure. Simply a figure that will provide a working preload subsequent to initial preload being lost.
From Lotus Elan workshop manual.

[2cams70]

No one is advising a pinion preload can be set by a nut torque figure. Simply a figure that will provide a working preload subsequent to initial preload being lost.
From Lotus Elan workshop manual.

Interesting - certainly not what Ford recommends for the diff that they designed! I think the Lotus manual is wrong. Usually a set figure for the pinion nut is only for diffs that do not have a collapsible type spacer and where the preload adjustment is done by shims and for those types of diffs the nut tightening torque is a lot higher than 30-35 ft/lb.

[Craven]

Once the crush spacer length has been set initially the preload on the bearings is set, 30-35 lbs/ft ensures the assembly is all up tight and when the new nut is staked again won’t come loose. Spacer/tube length will not change with 30-35 lbs/ft of clamping force.

[2cams70]

Once the crush spacer length has been set initially the preload on the bearings is set, 30-35 lbs/ft ensures the assembly is all up tight and when the new nut is staked again won’t come loose. Spacer/tube length will not change with 30-35 lbs/ft of clamping force.

Interesting too about 12-15 ft/bs for the bearing cap nuts. Not what Ford recommends and doesn't seem right. You certainly need a lot more torque than that on the cap nuts to get the cap spread amount right. If it were me I would not have any faith in that Lotus data.

[rgh0]

It was suggested to me by others that the 12 -15 ft lbs quoted was for the bolt for the bearing adjusters locking tabs. However when I built the last diff I did measure the torque on the adjuster to get the required bearing spread and it was actually around 15 ft-lbs. So I am not sure what it refers to but you should go by the bearing cap spread in any case.

cheers
Rohan

[2cams70]

It was suggested to me by others that the 12 -15 ft lbs quoted was for the bolt for the bearing adjusters locking tabs. However when I built the last diff I did measure the torque on the adjuster to get the required bearing spread and it was actually around 15 ft-lbs. So I am not sure what it refers to but you should go by the bearing cap spread in any case.

I'm surprised you actually measured the cap torque because it's something that's just not required when you do it the proper way by measuring the cap spread. The side bearing preload and hence the cap spread specification changes depending on whether the bearings are new or used also.

[rgh0]

I did it out of interest to try to understand what that torque in the manual referred to as the actual rebuild notes don't refer to it just to the cap spread. I made up a pin adapter for my torque wrench to measure it compared to the bearing cap spread

cheers
Rohan