Diff pinion nut

[frank_s]

I've just replaced the pinion oil seal on my 4A diff and Ive got a problem tightening up the castellated nut. When I started the job, the nut was literally only finger tight.... didn't think that was right but I hadn't had any problems from the diff other than the oil seal leak. Now putting it back together I'm caught between two settings in order to get the split pin in the nut. The diff turns freely with a looser setting (just a bit more than finger tight) and feels good, but if I tighten it up to the next hole, the diff stiffens up and there's significant initial resistance to turning, becoming freer as you keep turning the pinion flange. If I stop, it stiffens up again. Firstly, can anyone explain what's going on and secondly, is there a recommended minimum torque - or can I just tighten to the first, looser, setting?

Thanks

Frank

 

[RogerH]

Hi Frank,

           I think it is called the hypoid pinion flange and it has a mighty 85 - 100lbs/ft

It shouldn't finger tight.

You will somehow need to lock the output drives to torque this up. 

Not sure why it is locking up/stiffening.

 

Roger

 

[Dic Doretti]

Hi Frank

               Shims could be used under the nut to achieve the correct torque setting and fit the split pin.

               Cheers Richard

[frank_s]

Thanks very much Roger / Richard,

I'm not sure about this at all, the diff locks up at that torque.

Firstly, I've got the workshop manual and I noted the 85-100 ft/lbs torque for the hypoid flange in the torque settings table, but in the text I can see no mention of a hypoid flange (unless I missed it). Text and diagrams refer to companion flange, or pinion nut etc, and on diff reassembly, the text just says tighten the nut securely, no mention of a torque setting. That was my initial confusion. But secondly, I have torqued the nut up to 50 ft/lbs just to see, and the diff appears locked solid. I can't turn the flange (just to be clear, I mean the pinion shaft flange that connects to the prop).

Additionally, to add to my frustration, the oil seal still leaks past the flange shaft, and it doesn't feel like there is a tight fit of seal to the shaft. The shaft is in good condition, certainly not worn enough to cause this kind of leak with new cold oil. On inspection with the flange secured in place, there is approx 1/8inch gap between the top of the seal and the inner face of the flange - ie there's an 1/8 inch segment of shaft showing. That's probably a red herring though? The shaft is well inserted into the seal.

If this really needs to be torqued up to 85/100, then something's very wrong with my diff and probably explains why the previous owner only secured the nut just past finger tight. Any ideas anyone?

Frank 

 

[frank_s]

Correction.... I can turn the flange but it's very stiff and it isn't smooth - there's a hint of notchiness about it if that's any help?

F

[NickKerfoot]

The backstreet method for these was to mark the POSITION of the nut on the pinion shaft before loosening it.  Then do it up until your marks re-align....  some of these difs had a collapsible spacer to adjust the gear mesh, and the torque was applied to set this.   Re-application of torque may collapse the spacer more, and alter the mesh of the CW& pinion.

FWIW,  I used this method on my '4 ten years ago, and it's still OK with many miles since...

[John Morrison]

Think when you get your leak sorted there was a special Triumph tool to hold the flange

whilst the big nut is torqued down, if I am correct, you need to check the WS Manual, then I think our group has the tool,

get me a special number to confirm, and we could ship/post it to you.

John.

[RogerH]

Hi Frank,

            the pinion shaft needs to be solidly mounted in the casing to ensure that engagement with the crown wheel is continuously positive.

ref moss diagram  https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/clutch-transmission-drivetrain/axles-differentials/irs-rear-axle-differential-tr4a.html

The pinion shaft #24 passes through a number of bearings/spacers and seals and into the flange #37 that attaches to the prop.

The seal runs on this prop flange - there should be no gaps between seals and flange surfaces.

Clearly something is amiss.  When I got my diff back from rebuild in May the input and out put flanges were very very stiff to turn.

 

Roger

[frank_s]

Thanks everyone. I think I'm going to have to take the nose apart again. Sounds like something is wrong with the preload or something - shims wrong or something.  It's clearly been taken apart before and the fact the nut was on so loose suggests something was ignored. I'm not impressed with the new oil seal though....

Frank

[RogerH]

Hi Frank,

           I do not know a great deal about the build of Diffs but simply removing the front components may not tell you anything - other than the seal.

I'll send you a PM with a link to a cross section drawing - I think  it is the one in the manual

 

Roger

[Tr4aJim]

Hello Frank, 

Regarding the leak, when I replaced the pinion seal on my live axle TR4a, I noticed some wear marks on the pinion where the seal made contact (nothing I could feel, but visible nonetheless). So rather than risk a slow leak I also installed a “speedi-sleeve” that Moss and others offer for this purpose (one of the few items Moss/US sells cheaper than Moss/GB).

BTW - Here is post of mine, describing my efforts to replace the seal.

Jim

 

 

[Paul J]

Hi Frank

I had exactly the same problem on my 6 replaced the seal as the coupling was wet. I also found my coupling nut was not tight. After replacing seal and tightening the nut 110ft/lb the coupling went very notchy and stiff to turn. My remedy was remove the nut and machined a 2.5 mm thick washer to fit inside the splined coupling to make the end almost flush with the coupling. When tightened now it’s not loading the bearings as much and coupling turns smooth. 

I don’t think the seal was actually leaking, the oil loss was through the coupling splines, as the nut was loose letting oil out. 

That was my fix, not saying it’s the correct solution but it works. 

Best of luck

Paul

[Ian Vincent]

The pinion bearings are a couple of opposing taper roller bearings separated by a spacer.  This spacer may be collapsible or solid.  I am only familiar with the solid variety.  By using the appropriate shim pack with the spacer you set the distance between the two opposing taper roller bearings to deliver the correct amount of preload.  Once you have accurately set this spacing it doesn't matter how much you tighten the pinion nut you won't affect the preload because you are trying to crush the steel spacer/shim pack.

To achieve the requisite 85 ft lbs of torque, I use a stillson wrench on the pinion flange and the appropriate socket plus large torque wrench on the nut.

You don't insert the pinion oil seal until you have correctly set the preload because you will inevitably have to fit and remove the bearings a couple of times before you get it right.  Last thing you do before finally replacing the pinion is fit the seal.

Rgds Ian

[frank_s]

Thanks to everyone for your really helpful contributions. Having read Ian's post and looked at the cross-sectional drawing etc etc, I think I have a theory ....  when I started this job and removed the flange and old pinion oil seal, there were two shims on the outer face of the final taper bearing. I don't see any diagram that shows any shims at that point. The workshop manual talks about a shim pack and a compressible washer that should be fitted on the inner side of the bearing so that, as Ian has explained here, the pre-load is correct and the spacing between the inner and outer bearings is correct. Then I can see that tightening the pinion nut should have no effect on the spacing and hence on bearing load. I have just reassembled the diff as I found it but I wonder whether the previous owner put the shims in on the wrong side and then just didn't tighten the nut up fully to maintain smooth operation of the flange. How does that sound??!!

Frank

[RogerH]

Hi Frank,

         here is some bedtime reading.  I found it on Google but it is from our dear friend Ed-H

 

http://bullfire.net/TR6/TR6-38/TR6-38.html

 

Roger

Edited September 26, 2018 by RogerH

[frank_s]

Sorted.... put the shims on the correct side of the bearing, tightens up to required torque, turns smooth as silk. I can imagine what happened with the PO, manhandling the diff to put in a new oil seal, roller taper falls out, shims fall out and he puts them back wrong way. But why would you ignore this and just finger tighten the nut to compensate?? Oil seal was fine, it was just oil leaking past the splines because it wasn't tight. Makes you wonder....

Thanks

Frank

[RogerH]

Well done Frank,

              that took some thinking about.

 

Roger

[monty]

3 hours ago, frank_s said:

Sorted.... put the shims on the correct side of the bearing, tightens up to required torque, turns smooth as silk. I can imagine what happened with the PO, manhandling the diff to put in a new oil seal, roller taper falls out, shims fall out and he puts them back wrong way. But why would you ignore this and just finger tighten the nut to compensate?? Oil seal was fine, it was just oil leaking past the splines because it wasn't tight. Makes you wonder....

Thanks

Frank

Previous owners Frank! Any problems I have had are due to previous owners! Glad you have sorted it.

cheers.

 

3 hours ago, frank_s said:

Sorted.... put the shims on the correct side of the bearing, tightens up to required torque, turns smooth as silk. I can imagine what happened with the PO, manhandling the diff to put in a new oil seal, roller taper falls out, shims fall out and he puts them back wrong way. But why would you ignore this and just finger tighten the nut to compensate?? Oil seal was fine, it was just oil leaking past the splines because it wasn't tight. Makes you wonder....

Thanks

Frank