Dana 35 pinion depth - it is a thing apparently

[Fourpot]

At the same time as doing the stroker engine for my XJ during lockdown and the while after, I also did the diffs, swapping them for TrueTracs. I set the backlash reasonably well I think and did it all up. However, now that my exhaust is a bit quieter and I had occasion to have the rear seats out, I have noticed that the rear diff is a bit noisy, audible only on closed throttle i.e. a quiet time.

So onto the interwebs to remind myself how to set it up again (haven't taken anything apart yet), I discovered the importance of setting the pinion depth. Blimey! I didn't even know that was a thing! I replaced the pinion bearing several years ago and carefully set the crush spacer etc at the front, but the new inner bearing just went back in the same as the old one came out and I can't remember what the shim situation was.

Anyway, now I've seen how to do it, the one thing I can't find for certain is what the pinion depth should actually be. I'm think if I don't have that set up correctly, then messing about adjusting shims on the carrier will just be chasing the error?

So my question is, 'what should the pinion depth be for a 1998 Dana 35c on a Jeep XJ?'. I have seen 3.625" quoted for a '97 Dana 35 194R, and as far as I can tell, this is the same as my axle - Dana 35c 194mm according to the Equipment Listing for my Jeep, but I want to be as sure as possible. Or am I getting this wrong?

[V]

If you have the 1997 FSM go to page 801.

 

Do you still have the old pinion or a photo of the engraved markings in the pinion gear end? If so, you can use the variance table to find the shim adjustment from what it was originally assembled with.

Without the previous pinion variance number you will need special setup tools. I doubt there are any in the UK.

The depth from the centre line of the ring gear is 3.813" but you need the special tools to find it.

 

The original shim range possibilities are plus 8 thou to minus 8 thou. If you include zero, that gives 17 possible shim sizes, if the one you have is wrong, then you have 16 more to try by trial and error. Bear in mind that if you know what the variance number that is stamped into your current pinion, the trial and error set will be reduced to 8 possible shim sizes. You could be lucky and get it in one or at worst have to setup the gears 8 times. Record everything, all shim sizes, as you go.

Edited March 12 by V

[digger]

i would start with a simple check.

Why not take the cover off, degrease crown wheel etc, check backlash and then check pattern showing mesh with yellow paint or engineers blue. You should be able to see straight away whether its too deep (often noisy/whiney) or shallow (clonky)! This knowledge halves the possibilities!

I think my manual has a table showing pinion movement by shim size change(ask and I'll have a look). Beware I've not done a Dana 35 as i just changed mine for a Chrysler and rebuilt that and the D30 in front!

If the above tests look ok are you sure you don't have a prop balance issue etc before you start on the diff!

Edited March 12 by digger

[digger]

If you are faced with experimentally changing shims in order to get pinion depth correct I have a couple of ideas that may help save your patience and time. Just ask.

 

 

[Fourpot]

On 12/03/2023 at 18:33, V said:

If you have the 1997 FSM go to page 801.

 

Do you still have the old pinion or a photo of the engraved markings in the pinion gear end? If so, you can use the variance table to find the shim adjustment from what it was originally assembled with.

Without the previous pinion variance number you will need special setup tools. I doubt there are any in the UK.

The depth from the centre line of the ring gear is 3.813" but you need the special tools to find it.

 

The original shim range possibilities are plus 8 thou to minus 8 thou. If you include zero, that gives 17 possible shim sizes, if the one you have is wrong, then you have 16 more to try by trial and error. Bear in mind that if you know what the variance number that is stamped into your current pinion, the trial and error set will be reduced to 8 possible shim sizes. You could be lucky and get it in one or at worst have to setup the gears 8 times. Record everything, all shim sizes, as you go.

Thanks V, I used the same pinion as it was only the bearings I changed (and seals etc). I’ve seen a video on how to measure using straight edges and a vernier caliper (and a calculator for me!).

If I have to get the carrier out anyway, I’ll be able to see the variance number. 
Not looking forward to it, as getting the c-clips into the TrueTrac carrier was a real pain. I can’t imagine getting them out is going to be other than difficult.

[Fourpot]

On 12/03/2023 at 19:25, digger said:

i would start with a simple check.

Why not take the cover off, degrease crown wheel etc, check backlash and then check pattern showing mesh with yellow paint or engineers blue. You should be able to see straight away whether its too deep (often noisy/whiney) or shallow (clonky)! This knowledge halves the possibilities!

I think my manual has a table showing pinion movement by shim size change(ask and I'll have a look). Beware I've not done a Dana 35 as i just changed mine for a Chrysler and rebuilt that and the D30 in front!

If the above tests look ok are you sure you don't have a prop balance issue etc before you start on the diff!

Prop is fine Digger, new UJs and balanced less than two years ago. No vibes or anything at motorway speed etc.

[digger]

Gr8, is it straight? I bent one of mine by about 5mm over its length. It ran crap and I had to get it retubed, although it sounds like yours is ok.

Edited March 14 by digger

[V]

10 minutes ago, Fourpot said:

Not looking forward to it, as getting the c-clips into the TrueTrac carrier was a real pain. I can’t imagine getting them out is going to be other than difficult.

I am going to have the same problem on my Ford 8.8 in a couple of weeks.

 

Warn discontinued a fully floating 30-spline D35 conversion (#61748) some years ago. It was the only reasonably priced axle upgrade in the UK before the TJ was a thing. Being fully floating, it didn't use c-clips. There are still a few of them being driven about under old Jeeps from last century. Look out for the rear free wheeling hubs or drive flanges. Complete Super35 axle assemblies sometimes pop up on eBay so worth doing a saved search. 

 

If you ever plan to upgrade to a Ford 8.8, there are a number of companies making C-clip eliminators for them. 

[Fourpot]

 

[V]

Very good method, a nice find, thanks.

 

I think I would take the average of the bearing diameters and do all of the datum measurements twice flipping the straight edge to see if there is a deviation due to the straight edge not being truly straight. Half the difference would be the amount of correction for the curvature to add or subtract depending on which way round that you use the straight edge for the final set depth.

 

If you need to buy a digital vernier caliper to do this, DO NOT buy a plastic or 'carbon fibre' model from eBay as they are not accurate enough. A metal digital or even analogue vernier will be better. Check the stated error tolerance on accuracy before purchase. If you are measuring down to a one thou shim difference, the +/- accuracy should be at most 1/10th of a thou or smaller. Also beware of fake, top branded measuring instruments.

 

 

[digger]

Ah, I'm sorry I've not had time to watch yet but it looks like one of the methods I mentioned . I have a length of tool steel I use, in combination with a long throw dial indicator(mine's 4" travel and about about 10" long overall.).   At the end of the day, in my view, The thing that's key is the ability to measure where the pinion is and what difference a given shim changes its position by in terms of paint pattern.  Sort of, put in a thin ,then a thick shim.  Half way size should be in the middle and so on ,if that make's sense !

I wouldn't bother in your case though. If the paint pattern shows the pinion is in a bit  too deep then measure the thickness of shim pack total. 'Guesstimate' the %age you need to move it by, from the pattern and remove a shim accordingly .

Hope this helps!

 

V is spot on re tool accuracy. I've had issues with digital tools too. I don't like them either, give me a metal tool with a dial indicator every time. If I want to centre a job in the lathe for example I find its nearly impossible with a digital wizzing up and down, whereas its easy to see and remember the direction of swing with a dial. 

Perhaps i'm just old and old fashioned but I agree with V.

I have bought many new tools but you would be amazed at what engineers retirement redundancies one can buy in car boots or by using wanted ads in local paper. Just take some thing with known accuracy to check with!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edited March 16 by digger

[V]

To my amazement, a UK eBay trader has five Pinion Depth Gauge tool sets for sale at the moment at £551.98 .

[UKTJ]

5 hours ago, V said:

To my amazement, a UK eBay trader has five Pinion Depth Gauge tool sets for sale at the moment at £551.98 .

Been following this discussion, but with nothing I could add.  Was intrigued as to what the tool was, so did a quick Google search.  Found it on ebay at £551.98, but also what seems to be the same set at £410.99.  

[V]

Yes, I found that too. The cheaper is exactly the same but shipped from China and subject to import duty and VAT. The UK supplier is £141 more which probably covers import duty, VAT and shipping.

[UKTJ]

4 hours ago, V said:

Yes, I found that too. The cheaper is exactly the same but shipped from China and subject to import duty and VAT. The UK supplier is £141 more which probably covers import duty, VAT and shipping.

Are, OK, had not realised duty on top, I am not an ebay user so that wasn't clear to me.  Found it on Amazon from US for £536 including shipping and duty / VAT if that helps.

[digger]

That's ok but for £500 odd,  it would allow for an awful lot of time spent in trial and error, which is actually nothing like  that bad time wise,  as long as one is logical and  methodical !