Differential

[XR4Ti]

So I decided to plunge into the diff swap,

I did some serious damage to the rear tires last season...partly because I drive like a monkey, and mostly due to the stock 'open' diff in the rear. I was smoking the inside rear tires on every corner and losing tonnes of time. I`m swapping in an Eaton Posi LSD.

I'm also switching to a 3.36 rear/ring gear from a 3.64 when it goes back together. I'll have longer gears which will be nice because the stock trans has crazy short gearing.

It was a battle getting this 20 something year old diff out of the parts car and cracking the case and I`m glad it`s almost finished!

Diff out, cover off...



Diff apart...



Comparison of old and new diff...mmm purty...you can't see the carbon fiber clutch packs on either side but they're in there! you can however see the springs that preload the clutch packs with 400lbs of pressure.




Now I have to put it all back together. The guy that I had modify my side adjusters reversed the depth for the left and right bearing cup seals when pressing them in, so I have to get to a shop and have that fixed before going further.

Otherwise the only tricky part left will be grinding the case a 'bit' to make the beast fit in and setting the backlash of the ring gear...I`ll take my time with the deflection gauge when I`m doing the backlash for sure...

I`ll post with progress soon I hope.

[manotickmike]

[Chris_A]

Make sure you get the mesh pattern correct!

Otherwise the gears will not last very long.

You want to shoot for a rectangular sort of shape that is centered in the tooth face.

Are you setting up used gears? It's going to be a b!tch to get right for a gearing noobie.

[Chris_A]

Looking at the two carriers side by side... is there a ring gear to carrier bearing height difference? Maybe it is just the angle of the image.

What is the carrier break on this differential? Are you sure both ratios can run on the same carrier?

Gee, I'm "question boy" tonight...

[schmoo]

I know who I'm talking to if I ever change my rear end ratio

[XR4Ti]

Mesh pattern? I think that's what I call backlash? I'm going to be careful when dialing that in, before and after preloading the bearings. I'll be sure to look for a rectangular sort of shape that is centered in the tooth face!

To be honest I have no idea what I'm doing, so I appreciate the tips!

Good eye, the ring gear will be offset compared to before. I have a spacer for one of the stub shafts to compensate and thus the need for a little grinding on the case.

That's also the reason I have to fiddle with the bearing carrier seals...11mm inset on one side and 4mm inset on the other side was reversed....it wouldn't make a difference other than the bearing cup being slightly thicker on one of them.

Side adjusters showing seal inset depth...



Stub shafts, one with spacer...




The Eaton will be matched to a 'used' ring and pinion gear yes...they are both in good order though.

The 3.36 ring gear is from an 'automatic' xr4ti and is plug and play...it was a surprise when I found it in the parts car, cause that XR is a manual too!...someone was playing before me.

I'm using this doc,
http://www.mc2racing.com/tech/20081104a/index.html

Feel free to critique any potential miss-info's.

[Chris_A]

Browsed the article you linked... Danger Will Robinson, danger!

They don't mention tooth pattern anywhere there.

Maybe there is something unique about your differential housing where it doesn't need to be setup for carrier pre-loads and gear mesh pattern. I doubt it though.

The side adjusters set the depth of the ring gear relative to the pinion. It can also set the differential carrier bearing preload. The backlash is effectively the play or slop between the ring and the pinion. Nothing more. It does not determine whether you have a good pattern or not.

Usually you will use shims (or adjusters) between the carrier bearings for the differential itself and/or the pinion to set depth relative to the other parts. All these are independently variable, hence the need to check that the ring gear and pinion gear are meshing correctly (i.e. have a good mesh pattern).

Here are three different articles that discuss setting up a differential:

http://www.ford-trucks.com/article/idx/ ... Setup.html

http://www.differentials.com/install.html

http://www.ehow.com/how_2159877_set-up- ... ntial.html

They describe differentials that are different from what you have in front of you. From what I can see of your differential a Toyota (Aisin) truck or Land Cruiser differential could be similar.

http://www.4x4wire.com/toyota/tech/gear_setup/

You didn't mention it in your post but I will for the sake of completeness. (edit: yes you did) The ring and pinion gears are matched sets. If you change the ring gear you must also change the pinion gear to the one that goes with it. This is not just a matter of whether or not the tooth pattern meshes but a matter of the ring and pinion gear machining process. You should not take two sets of 4.10 gears and interchange the ring and piinons between them for example. They are paired when cut and must stay together.

I setup a differential in a Jeep once (Dana 44). It's one of the biggest PITA jobs I've ever done. It's very fiddly and beyond being able to say I've done it once I got no joy from it. When I built new axles for the current Jeep project I contracted that part out.

There must be marque specific guides on the Merkur/Sierra forums on this stuff? What about the FSM?

HTH

[XR4Ti]

Hmmm,
One thing that may differ from your gearing experience is that this is an IRS diff. I had a really confusing convo with a guy here at work, and when he realized that my diff was for a IRS setup, he was like 'ohhhh never had one of them'. I have even less clue about a solid rear axle diff ...and I'm assuming your Jeeps have a solid rear. I could be wrong though...

I never removed or touched the pinion gear in the diff that's getting rebuilt, and I know now that the pinion gear (not the diff unit) gets shimmed at the factory to set the right 'mesh' with the ring gear. It will be the same ring and pinion gears when it goes back together so they will be matched. Assuming the backlash is correct, the mesh should be the same as before.

There is only room for lateral movement of the ring gear when it goes back together and that is done via the side adjusters. The bearing preload is also done via the side adjusters.

That install doc was actually off the Mc2racing.com website and is definitely specific to my car. I got the eaton and the parts kit from the same guys. Didn't you see the Merkur at the bottom? It even has my wheels on it. (I got them from the same guys too)

There are a number a guys from the Merkur community that are running the Eaton setup from Mc2racing, and I'm certain I would've heard negative things in the forums if anyone experienced any failures due to bad installs, poor instructions etc...

Needless to say I appreciate your concern and advice Chris! You've scared me a little, but I'm still moving forward into the unknown! I do have the FSM and I'll check it as well to be triple sure.

What is it with you Jeep guys, thinking you know everything there is to know about gears anyways? I'll be fiddling with it this weekend so I'll let you know how it goes.

[Chris_A]

Hmmm,
One thing that may differ from your gearing experience is that this is an IRS diff. I had a really confusing convo with a guy here at work, and when he realized that my diff was for a IRS setup, he was like 'ohhhh never had one of them'. I have even less clue about a solid rear axle diff ...and I'm assuming your Jeeps have a solid rear. I could be wrong though...

I never removed or touched the pinion gear in the diff that's getting rebuilt, and I know now that the pinion gear (not the diff unit) gets shimmed at the factory to set the right 'mesh' with the ring gear. It will be the same ring and pinion gears when it goes back together so they will be matched. Assuming the backlash is correct, the mesh should be the same as before.

There is only room for lateral movement of the ring gear when it goes back together and that is done via the side adjusters. The bearing preload is also done via the side adjusters.

That install doc was actually off the Mc2racing.com website and is definitely specific to my car. I got the eaton and the parts kit from the same guys. Didn't you see the Merkur at the bottom? It even has my wheels on it. (I got them from the same guys too)

There are a number a guys from the Merkur community that are running the Eaton setup from Mc2racing, and I'm certain I would've heard negative things in the forums if anyone experienced any failures due to bad installs, poor instructions etc...

Needless to say I appreciate your concern and advice Chris! You've scared me a little, but I'm still moving forward into the unknown! I do have the FSM and I'll check it as well to be triple sure.

What is it with you Jeep guys, thinking you know everything there is to know about gears anyways? I'll be fiddling with it this weekend so I'll let you know how it goes.

LOL No worries Steve....

I just want to make sure you are completely armed to take on the job. I want to see you get 400,000 miles out of the ring and pinion gears, not 40.

All I can suggest is that you read the FSM before you button it up. I'd still get some marking compound to check the pattern.

If the pinion gear has not been removed from the housing then that is half the battle.

[XR4Ti]

If the pinion gear has not been removed from the housing then that is half the battle.

Nice!

Hellooo in there pinion gear...



Ring gear loosely bolted to the Eaton...

[John Powell]

I watched someone set up a diff many decades ago, and there were two things that I learned. The first is that there are two set-ups, one for general use and one for racing. The setting for general use is a compromise between strength and noise, and you should get an oblong contact patch in the middle of the ring gear teeth, both lengthwise and in hight. The setting for a race car ignores noise and goes for strength, and the contact patch should be ... and sorry fellas, but here I forget whether it's the toe or heel of the ring gear teeth. Also, GM apparently has the best marking dye to show the contact patches, but I don't know where you might get some. Oh yeah, there was a third thing I learned; if you're not sure you can do the set-up properly, shop the job out to an expert.

[Chris_A]

John is correct on the GM marking dye. It is reputed to be the best stuff out there.

[Morphy]

I can attest to the fact that Steve drives like a Monkey.

Now get off your ass and get that baby installed. Should be awesome for ya once it's in.

[XR4Ti]

Well I tried to find the GM marking dye and the GM dealers raved about it as well but didn't carry it in stock or even use it.... (they did however have the 'friction modifier' fluid that needs to be added to the 80w-90 when it gets liquids)

I found this article on the compound usage and explains it pretty well. I may still find some, but I'm also ok with just dialing in the backlash with the deflection gauge. I read some guys use toothpaste...hmmm



Opened the case up on the gear side and wiggled the beast in. It wasn't easy trying to fiddle this thing in, but it's in!



Now to dial it in.

[XR4Ti]

Got it in the car today.

Set the backlash to 5 thousands of an inch (five of the little notches on the dial) It was an interesting procedure once i figured out how it all worked. I nailed it in about 20 tries, the preloading was weird at first.




Being that I never found any actual marking compound and that I still wanted to check the meshing, I tried liquid paper, toothpaste, and white lithium grease. The lithium grease gave the best visible pattern. I'm happy with the pattern, it's almost bang on the previous wear from factory.
Here's a pic of the teeth with toothpaste.





No leaks or weirdness after a few test runs and it's locking up like crazy back there. Next pic should be of my ceremonial 2 wheel burnout!

and maybe a pic of the guts inside the one I took out today...I have a feeling there's going to be some busted guts.

Also swapped out a sticky drive axle and so far the 3.36 feels like it's on the money.

Hooray for traction!

[el_torpedo]

Did you use Colgate Total? Less tartar build up and it leaves your diff minty fresh!

[Chris_A]

Did you use Colgate Total? Less tartar build up and it leaves your diff minty fresh!

LOL!

[schmoo]

Wouldn't it be nice if diff and tranny fluids were in fact minty scented?

[manotickmike]

Wouldn't it be nice if diff and tranny fluids were in fact minty scented?

Goodness, yes. I suggest we submit that idea to the oil companies.
I recently hauled a diff out of storage for a pal, and forgot that the plug had been donated to another project. A replacement was promised, but I'd forgotten about it, 'til I moved that diff. It puked all over my leg, and the floor. Funky. I can still smell it in the garage. All synthetic for me now.

Go, Steve!
I suspect we'll be swapping out that trans for a B+W T-5 any day now... I'll be listening for the bang when your T-9 lets go, just so I have a heads up that you'll be calling.

[XR4Ti]

I'm praying to the Merkur gods that the T9 makes it through this year. I don't have a T5 on the radar till next year.

For those that don't know, a 85-93ish Borg Warner WC T5 transmission from any Mustang fits into a Merkur with a few easy mods. They are easy to find and the gear ratio choices are a plenty. The T5 is MUCH stronger and smoother than the stock weirdo Ford T9 they decided to put in the Merkur.

Look at all them choices....

[Chris_A]

You might find this helpful when scrounging.

http://moose.ca/borg-warner-t-5-identification-numbers/