Gear setup - pinion shim starting thickness check please...

I have a 3.91 '741 in my coupe at the moment, I picked up a Richmond Gear 4.10 gearset that I'm going to install and need some recommendations and a check of my calculations.

The new gearset is for a '742 case, which previously had a 3.55 factory ratio.

OK, so I measured all the parts and am looking for some recommendations regarding the starting point for the pinion head bearing shim.

Here is what I have so far:

1) Pinion head thickness dimension (from end flat face to where the bearing and/or shim sit on the other side)
OEM - 2.575"
RICHMOND - 2.627"

2) OEM pinion shim
0.090"

3) OEM gear marking
'-1'

4) RICHMOND gear marking
CROWN markings => 'I57 BL007'
PINION markings => 'I57 CD 2.720'

OK, so I understand the Richmond markings, set backlash to 0.007" and measure the pinion installed in the case to centerline of the cap of 2.720". Great...but I do not have the tools, so another method is needed.

To simplify things I have purchased another NEW Timken pinion bearing which I will hone out a tad so it's a slip-fit onto the new pinion. That will ease the trial-end-error gearset mesh pattern reading. Before I get there though I would like to start as close as possible to what the ideal spot may be.

OK, so the stock gears were using a 0.090" shim and given the difference in pinion head thickness between the two (0.052) that gives me a left-over thickness of 0.038" (0.090-0.052) needed to get the new pinion into roughly the same operating spot as the previous OEM install.

Does the above make sense?

Oh, I am no pro at this...ha ha, you can tell for sure, but I did successfully setup my previous 3.91 gearset for the '741 case and it's been holding up pretty well, no noise, no problems that I can report. I remember measuring things repeatedly back then, but it's been a few years so I am practically re-starting the learning effort on this topic.

Thanks!

I start with the .090 shim in the 742 case. Don't even think about that .038 shim.

Just put that big thick one in and your set-up bearing and go from there.

Gus

http://www.ratechmfg.com/pop_up_order%2010007.htm

This tool will be your friend.

Put the .090 in it. Mock it together maintaining the correct pinion preload and backlash. Run the pattern and go from there.

Alright, thanks for the feedback guys.

I did order the Ratech tool. Read about this a while back, was curious about it's use (price is reasonable compared to the other options) but didn't really know/understand that the aftermarket gear companies would be showing the carrier depth number and using that to properly locate the pinion (like I said, a pure amateur here). Hopefuly it's here within the next week.

In the meantime, I'll take a stab at this using the two approaches: 0.090" and my 0.038" shims. Mesh pattern pics coming up as soon as I have this done...

Well, that was a short-lived purchase...LOL, sorry, but in today's day and age of global e-commerce I honestly find it hard to believe that businesses still exist out there that have not figured out how to deal with shipping outside of their country.

Brief Paypal only response (no other email) which came with my refund payment: "Note from Ratech inc: We do not export".

Anyways, for non-US Mopar fans, you apparently will not be able to purchase this directly and ship to your home.

It is because the shipping charge will always be wrong on canadian purchases, it is a no win situation for a business as they either lose money or get negative feedback, or a load of s#@t at the post office. The first advice I ever got in about 2000 on ebay sales was never ship to canada, I did not listen and every deal had a problem, shipping doubling, and fraud accusations at post office or claims it never showed up, box showed up empty, all kinds of fun stuff. They are not stupid, just well educated in my opinion.

Let's clarify something, nowhere did I accuse anyone of being, as you put it, "stupid".

Here is the thing, over the years I purchased from US businesses countless times. Sometimes it was a single small item, yes, lots of them off of eBay. Other times, it was a box full of stuff from a mom&pop type of a shop. So while I agree and recognize that shipping outside the border of your own country is a bit more complex, it is by no means an insurmountable obstacle.

Believe me, if you think it sucks for the business, imagine the damned shipping charges, then customs duty and oftentimes a carrier border agent duty a poor Canuck pays...yeah, that stings!

I understand what you guys go thru believe me, it seems some postmasters are worse about it than others. Anyway good luck with the rearend.

Guys...bringing this one up because I am literally in my garage, having completed the SureGrip assembly with new clutches, new carrier bearings pressed on and a test-fit pinion bearing (which has been reamed out for easy slip-fit) on the pinion and the pinion bearing pre-load completed.

So here is the thing, I do not understand how having achieved the 25in-lbs turning torque I can guarantee that once everything is fully installed (mesh pattern is good, real pinion press-fit bearing used, etc) and the pinion nut is torqued to the full 210ft-lbs value, that same bearing pre-load will be maintained?

As I started installing the pinion nut and took out all the clearance I saw the turning torque increase, makese sense. But once the 25 in-lbs was achieved I stopped tightening the pinion nut, yet for sure, that torque was nowhere near the final 210ft-lbs value, and I'm pretty sure if I had continued to tighten the nut the turning torque reading would just get bigger.

For clarity's sake, this is a '742 housing, so I have the following combination on the pinion (in sequence, from gear teeth to the yoke): pinion head, 0.090" factory shim, bearing, 0.015" factory shim, bearing, 0.015" factory shim, yoke, pinion nut (nut & washer assembly). As per the previous feedback provided in this thread, I basically re-used all the same shims, in the very same locations, as the OEM gear setup.

So am I missing something here in my understanding how this works??? LOL

I thought that if my bearing pre-load shims are correct I should arrive at a turning torque value that would not continue to increase regardless of how much more I kept on tightening the pinion nut. That way I make sure that upon final assembly the combination I am measuring during my trial-fit remains the same. Yet all the documentation I have specifically says not to tighten the pinion nut to the fullest during the pinion bearing pre-load check.

More shim behind front bearing, the one behind the yoke = less pinion preload, less shim= more preload. You need more shim behind front bearing, that will change if your pinion depth shim changes also.

Isn't the 742 like a dana, one has to add or take away shims (behind front bearing) for pinion preload?

No need to fully tighten nut during setup just snug it till you get play out of bearings and some preload. Once your pattern is right then adjust shim.

Alright you guys. I understand what 4406bbl said...makes sense.

OK, so here are some pics of the pattern, this is using the OEM 0.090" pinion shim (see beginning of the thread regarding my thinking to go to a thinner shim).

The pics are in 'sets', meaning the same spot on the ring gear (4 in total, spread 90 deg apart), but showing both the drive and cost sides.

1)




2)




3)




4)





My conclusion: I think the pinion is too close to the ring gear. I am basing this on the pattern showing a pretty flat line at the root of the gear.

So what do you guys think?

Given that it's a slip-on, slip-off, I'm almost inclined to yank it, toss the thinner shim in and check it out...but how much of a change to make???

It's close. 2, maybe 3. 4 would be too much. Maintain the preload and backlash everytime you check it. Pulling the pinion out a couple will only open the backlash up a few as well. May not have to change it.

Yes you could bring the pinion out just a hair but thats not a bad pattern for a used gear.
If you keep getting different pre-load readings make sure you don't have any burrs on the shims. I like to de-burr all the flash off the edges with some 1200 while I'm measuring and marking them.

Gus

Alright...more data!!!

So I did two more setups:

1) 0.072" shim
2) 0.086" shim

Here are the results:

1) 0.072" (only showing a single ring gear spot because the results are obvious I think)






2) 0.086"



















So here is what I'm thinking:

1) as someone who rarely ever does this (OK, this is only my 2nd set I've ever done) I'm amazed at how much of a difference a tiny amount of shim change makes => see the difference between 0.090 and 0.086

2) the 0.086" pattern looks great on the drive side, but on coast side it is a little too close to the toe, although everything I read says this is fine

Therefore, given the choice between 0.090 and 0.086...which one would you guys go with? I am thinking 0.086 is the way to go.

This is a street car, so all things being equal, a quieter gear is the only benefit I can think of that would drive towards one or the other.

Thanks everyone!

If you are paying attention .001 makes a difference.

The 086 looks fine on the driveside. Ok on the coast side. Sometimes you just have to live with what you get with the gears made today. What BL? That can be moved around a few to fine tune it as well.

The gearset markings indicate design of 0.007, so that is how I set it up as well. Richmond does state though that it's allowable for up to 0.004 variance, so 0.011 at most, I would prefer to run the tighter bl though.