110 300TDi drivetrain improvements - recommendations please!

[L19MUD]

3 hours ago, Peaklander said:

It's not too late and I will think about it again as I drive down the M1 in a few minutes to drop it off.

The extra £300 when you are already spending a lot feels worth it to me for the upgrade and means it is all done at the same time. Plus selfishly I would like to know your thoughts on it for when I do mine 😀

[Peaklander]

I re-read the whole thread when I arrived at Ashcrofts, before I knocked on their door. Opinion re the centre ATB is split somewhat, (as it is in our household) but on reflection I cancelled the HD cross pin and went for the ATB. Net increase is £255+VAT. 

My New Year resolution was to not prevaricate. This thread has helped me make informed decisions rather than just ponder the inputs, so thank you very much everyone. 

[uninformed]

Good choice IMO. Enjoy 👍

[Snagger]

I think you made the right choice on the centre diff.  If you are already spending a reasonable sum on the Labour and other parts, it’s worth biting the bullet and perhaps paying a little more to increase the capability and ruggedness of that assembly.  If it prevents possible future “grenading” of the centre diff, as well as giving better performance over mixed or patch surfaces, then it is a worthwhile upgrade.  I’d still say the same for the front diff too, even if you do end up with an unconventional result like Sigi; you’d be upgrading for the strength and reliability, but I imagine the price of the ATB being little more than the price of the 4-pin after all the labour, but with higher capability.  The rear diff could be done any other time, since the budget is getting a little stretched with the overdrive and potentially new tyres on the cards.

I agree entirely that new traction aids are pointless without decent tyres.  Having locked diffs throughout is still not going to move the vehicle if you have 4x zero grip.  As for sizes, it comes up repeatedly that for most, standard works best - tall tyres will increase ground clearance and are much better for greater footprint than fat tyres as they don’t increase drag, cause tangential loadings on bearings and stub axles, and don’t increase the chances of aquaplaning like fat tyres do.  The trouble is that any significant diameter increase really needs a final drive (diff) ratio swap to retain the torque needed off road (and for speedo calibration).  But the MoD, Mountain Rescue services and Camel Trophy all stuck to 7.50s for a reason.

Whatever you finally end up with, I hope it gives you a good result.  It makes you baulk when so much comes up at once, especially if unexpected.

[Peaklander]

Today I moved onto the front axle and continued to remove the hubs as complete units. The panhard and track rod joints released easily with taps and the 14mm screws into the axle were easy to remove. I used one of the dangerous non-reversable ratchet spanners and it makes it an easy job - once I checked that nothing was going to get stuck.

The hubs with swivels and driveshafts sticking out are now on the bench.

Even though I committed to the purchase of a complete new final drive from Xcess 4x4, Nige has been kind enough to let me ponder the best way forward and refunded the deposit so that I can take my time and have a look at mine. I know I said that I was going to stop prevaricating but I want to in this case.

I was prepared for the weight of the final drive unit but maybe I should have raised the front a bit higher. It is quite a lump.

Next is to do the backlash check - everyday is a school day.

 

[Snagger]

Looks pretty clean.

[Anderzander]

Very clean.

[Peaklander]

It hasn't been cleaned but does look OK. There are no obvious marks on anything. I have a little DTI gauge, not very brilliant but the backlash doesn't appear to be much at all - maybe only 5 thou. I think that's too small but I am hopefully going to borrow a better gauge. I will be able to check the crown wheel runout too then.

[uninformed]

Good work. If you do by chance strip it down, do not mix up the carrier bearing caps. They are fitted , then machined. They should never be swapped around or from diff to diff. 

[Snagger]

0.1-0.17 mm is correct.  5 thou is about 0.13mm, so nicely in the middle to close part of the range.

[Peaklander]

I have borrowed a much better DTI and stand from @nickwilliams (thank you Nick) but I forgot to ask if he has some engineers blue. I am going to check the runout and backlash and then the mesh and I will post results.

Also I am going to ask Ashcrofts about using an ATB in just the front, with the unmolested Salisbury in the back. I know that it will provide some self-centering and that opinions on fitting it 'alone' are split but I really do like the idea of it being able to deal with slight front axle wheel spin, especially in winter around here.

If the crown wheel and pinion checkout OK, then I will keep them and fit either the 4 pin centre or the ATB. I would hope that doing this won't introduce any noise into the final drive. The cost premium at Ashcroft is £90 (ATB v 4 pin).

I am not sure whether to do it myself or not. Would you replace the pinion bearings or only if there's signs of wear? I have read and watched a lot of advice in the last 36 hours and from what I can see, I don't need to worry about getting a pinion height setting block but would expect to need a selection of new shims. I will be using Timken bearings and so dimensions will be the same. Anyway isn't the initial pinion height setting (with the block) the initial (close) guide and the final test and set-up is by looking at the meshing? That would indicate whether final minute pinion height adjustment is needed, which would the deviate from that initial height setting anyway.

[Snagger]

If you are replacing the pinion bearings and seal but not the gears, then it’s an easy job - the shims won’t change.  It’s a simple case of strip, clean and reassemble.  Still worth doing a contact pattern test to be sure.  If you can’t get some Prussian Blue, then some oil paint will work.  I used black oil paint as I had some for my model making and couldn’t get the Prussian Blue locally.  It worked well enough, but a light colour may be easier to read the pattern.  Don’t use silver or grey - you’ll never be able to see the pattern against the steel!

Even if you do change the gears, the pinion depth shim is very unlikely to need to be changed, but you’d need to check the preload before fitting the seal to make sure the preload shims are right.  I doubt they’d change either, but it’s worth a test. 

I think the only time you are really likely to be changing depth shims is if you use another brand of bearing, as happened to another forum member recently.  So stick to the correct Timken stuff. Ashcroft sell a kit of bearings and seals for the job, and also have shim kits if needed.  I used both and got good results, though the depth shim was kept original (despite fitting an aftermarket ring and pinion of a different ratio; I did use a combination of the new preload shims).

[uninformed]

I know I’m repeating myself, but if you are doing it yourself, check the gear pattern with die etc before you strip it down , take photos etc and on rebuild set the same. Given that it’s in spec you are trying to set it in the same mesh as it has worn in to. 
 

A new pinion flange might be worth it as well. I like the round ones. 
 

I personally don’t like the newer flange head CW bolts. Not because of their design or class, I feel they are average quality and are too short. But that’s a whole other subjective discussion. 

[Peaklander]

I haven’t had time to add the detail to the thread but I will. I have done a mesh check and will post the photos and the dti results tomorrow.

I have lodged an email at Ashcrofts about the ATB and then I will be able to choose between it or open 4 pin and DIY or buy the expertise 😊

[Tobias]

As I wrote above. An ATB in front only is MARVELOUS!

Aids in steering, self centering, avoids the heavy understeer in seriously slippery conditions, such as deep mud or snow, that you get with and ATB of locker in rear only. IAfter my experiences with rear only, front only and both, I would never put in rear only. Front first, then rear!

 

T

[Snagger]

42 minutes ago, Tobias said:

As I wrote above. An ATB in front only is MARVELOUS!

Aids in steering, self centering, avoids the heavy understeer in seriously slippery conditions, such as deep mud or snow, that you get with and ATB of locker in rear only. IAfter my experiences with rear only, front only and both, I would never put in rear only. Front first, then rear!

 

T

That is very interesting, and especially useful as it is real experience, not theory like I am working with.  I will be fitting both, but your point is contrary to established “received wisdom” and a useful counterpoint, much like the internet riddling notions that a Tdi will destroy a Series gear box, any off road venturing Defender needs a suspension lift, big tyres are always better and so on.

[Peaklander]

The reply from Dave Ashcroft is that it is OK to fit an ATB in the front and at the same time keep an open diff in the rear. So that, together with the experience of @Tobias and other opinion means that it's a real choice for me now. Unfortunately Ashcrofts are a little guarded about the cost to rebuild. The base is £95+VAT but I don't think this includes the pinion seal or any bearings or shims. I think a max of four bearings are needed at the pinion and the two carriers. Also there's a seal or two and potentially a new pinion flange but there was no oil leak so it will probably be ok. I probably don't need to buy the shim pack if Timken bearings are being used as it 'should' go back into the same position.

I have done my first checks of the current unit but will repeat them and I can't see any damage at all.

There's obviously a method to learn in handling the DTI and getting it positioned securely and reliably. There's a technique to painting of the marker for the mesh test too!

First results are Crownwheel runout  - 0.05mm (target 0-0.10)

 

and backlash 0.15mm (target 0.08-0.18)

 

The mesh looks like this - now I am simply putting them out here for now. I don't know if I have enough detail to make a proper assessment or not. From what @uninformed advises, if it looks ok then I would be trying to replicate with the new setup.

 

 

 

 

 

Edited January 24, 2022 by Peaklander
Corrected a few things

[Bowie69]

Anyone offering to rebuild a diff and not replace the bearings and seals as a matter of course are not offering to rebuild a diff, IMHO. Suspect some wires crossed there.... Bearings are cheap, labour is not.

[Peaklander]

No not crossed, just my explanation maybe.

If you buy their ATB then they will fit it for £95+VAT, assuming the diff is in good running order. I don't know what their assessment is but I tried to find out how much it would cost if it requires new bearings etc and that is where they said they couldn't, they would need to see it first. I am only trying to assess the relative cost of them or me "rebuilding".

[Bowie69]

Ah, hmm. Well I guess there comes the variables. I'd just choose to replace anything that is a service item anyway.

[Snagger]

I think for the £60ish of their bearing and seal kit, it’d be a shame not to replace them.  I could have reused the bearings that were in my locally sourced unit, but you never know the providence of second hand parts or cars, and yours has done enough miles to warrant new bearings.  The rebuild charge would just be labour.
 

 The contact pattern looks good.  LR say to only look at the drive side, which is the convex side.  That has a nice pattern in the middle of the teeth.

[toenden]

10 hours ago, Snagger said:

That is very interesting, and especially useful as it is real experience, not theory like I am working with.  I will be fitting both, but your point is contrary to established “received wisdom” and a useful counterpoint, much like the internet riddling notions that a Tdi will destroy a Series gear box, any off road venturing Defender needs a suspension lift, big tyres are always better and so on.

For what it is worth, my tractor (jd 6400) runs an atb in the front and a manually opperated locker in the rear. As Tobias notes, it is brillant in going the way the front tires are pointing and the rear locker have never needed use in my ownership (in fact the contact is rusted solid). 

My theory have always been, that this setup ought to give the Best of all worlds in competition, leaving you with the most power on both front tires but able to steer. Haven't tried it yet though...

/mads 

[Sigi_H]

13 hours ago, toenden said:

My theory have always been, that this setup ought to give the Best of all worlds in competition, leaving you with the most power on both front tires but able to steer.

Just to correct this a little bit: When the front is locked it is hard to steer because both tires run the same revs. It really depends on the ground. Steerability remains good enough. Best is to have the final direction before the axle is locked.

But the car even tends to go straight, when the centre is locked.

 

 

[Peaklander]

@toenden is talking about an ATB not a locker @Sigi_H 

[Sigi_H]

Sorry, didn't notice it.