03 IRS: Speed sensitive 'clunking'

[Booksix]

Also, thanks for the offer of the clutch pack rebuild phone convo! But I'm thinking it's going to need a lot more than just clutch packs as I still have not found the source of the clunk (cv joints checked out ok when suspension was at ride height).

Someone on yahoo answers suggested excessive lateral runout on a tire but I'm not so sure. First off, it would need to be radial runout for it to cause an up and down motion, right? Second, what are the odds that both rear tires have a broken belt or something that would cause them both to bounce? Third, I had a vibration about 70 mph with the straight axle (tires and DS need balancing) but this is at 5-10 mph. It has to be in the IRS somewhere, otherwise I would have noticed it before the swap.....? right?

 

[03SVTCOBRA10TH]

yes, you are correct. vibration and wobble yes, clunk no.

Also, the yahoo answer guy was close, I think you might find excessive runout on the IRS wheel bearing, but that would not give you the clunk. To test this remove the IRS knukle and put it on a vice, then trun it. You can see a video demo of this if you search for a guy named "burntire" on mod fords.

Lets think about this, the axle halfshafts fit into a splinded side drive gear, unless the splines have a loose fit they will be quiet. That side drive gear turns with another gear called the spider gear, if the gears have worn due to abuse or due to the clutch packs being worn and then commpressing due to the S-spring expanding, they will make noise and have excessive free play. Then the clutches turn the steel plates that are splined, no noise here, then that turnes the diff. The diff turns on the ring gear, which should not have any noise and has ten bolts holding it to the diff. I have seen ring gears with multiple bolts backed out due to no loctite, but then the diff locks up and will not make th noises you have. The ring gear turns from the pinion gear, which is held in place by a top and bottom bearing and pinion nut, so no noise there. The pinion nut also holds the pinion flange to the pinion shaft they are splined and will not make noise.

I would bet that a re-pack of the clutches will take care of 90%-100% of the noise and if you replaced the side drive gears and spider gears along with a new S-spring, you would solve 100% of the noise, asuming that the CV's are ok and the IRS bearing is ok and the drive shaft U joints are ok.

If I can help let me know. Good luck!!!

 

[Booksix]

The axle bearings are both new, although, one did seperate durng the install (pressed it back together and continued the bearing install with a bigger socket in the press). But even if that was problematic the up/down motion wouldn't carry through the IRS to the other side.

As for the rest, will be able to tell visually if the drive or spider gears are toast? I'd love if I could get by with just a clutch job. Maybe ill just start there (after inspection of course). I can also check my pinion depth and re-adjust backlash in the process. What's the minimum parts I need just to do the clutches?

 

[03SVTCOBRA10TH]

Ford Racing M-4700-C - Ford Racing 8.8 in. Axle Installation Kits - summitracing.com

Basic hand tools, a 2x4 (wood) about 10 inches long, a hammer, and gray RTV sealant.

Those things plus 30 mins and you are done, once you have the center section out of the car.

 

[Booksix]

Sweet! Thanks. Once again, I'll post updates!

 

[Booksix]

I followed your link but it says for non-IRS only. What about this kit (also way cheaper):

Ford Racing M-4700-B - Ford Racing Traction-Lok Rebuild Kits - summitracing.com

Edit: nm, I check the ford racing site... This kits good


Also, what should my pinion preload be on the old bearings?

 

[03SVTCOBRA10TH]

If you use new bearings I like 25inch pounds with a dial torque wrench, if you use the old bearings I like 16-18 inch pounds. Make sure you use INCH POUNDS and NOT FOOT POUNDS!!!! The pinion nut will need to be tightened to about 200-210ft/lbs if you use a new crush sleeve, to do this out of the car I just got a 3 ft long angle iron at Home depot and drill 2 holes and cut a C notch so it lays on the pinon flange and bolts up. I let the angle iron lay on the table and then torque the pinion nut, checking rotational torque with the inch pound dial torque wrench every 10 foot pounds from 180ft/lbs on the pinion nut.

 

[03SVTCOBRA10TH]

I followed your link but it says for non-IRS only. What about this kit (also way cheaper):

Ford Racing M-4700-B - Ford Racing Traction-Lok Rebuild Kits - summitracing.com

Edit: nm, I check the ford racing site... This kits good


Also, what should my pinion preload be on the old bearings?

Summits notes are incorrect.

You want the M-4700-C kit as the C standsfor carbon fiber clutches.
The B kit is for the organic clutches that come in the mustang GT's.

 

[Booksix]

Ok, initial inspection shows no damage to any of the gears so I'm think I'm good there.

http://www.moddedmustangs.com/forum...d1204597023-trac-lok-rebuild-how-100_2825.jpg

So, considering that pic is a diff with shot clutches mine are definitely toast! I'm actually wondering if the clutch pack depth will even be in spec when I pull and measure them; I say this because, if they are not, I won't know what dimension to shim the new packs to...?

I checked backlash and it appears to be around .004". Way too tight. So, I was hoping I could get direction on this as well. The way I understand it is there are shims on each side of the carrier and by simply removing them from one side and placing them on the other side you can tighten or loosen the backlash. Is this correct?

edit: I checked the wear pattern and got this:

If I've looked at this and the chart right, it appears I need a thinner pinion shim...? I know they are hard to see, but it looks like the second row down on this chart:

https://w05.dealerconnect.chrysler.com/service/mds2002/serviceInfo/en_US/80d04e58.gif

 

[03SVTCOBRA10TH]

No wories, the clutch pack kit comes pre-set to the proper depth. It has new steel and clutch plates as well as shims. Just toss the old stuff away.

Back lash should be set at 0.008", and I would guess that your pinion depth needs to be re-shimed as well. Do you have the Ford pinion depth guage tool??

What gears did you say where in there?? Stock 3.55's???

I think we are getting closer to the cause of your clunking......

 

[Booksix]

I hope so!! Yes, stock 3.55's but the seller put them back in for me in place of Motive 3.90's. Guess I'll be needing to order a pinion kit as well! No tool, I was going to shim based on wear pattern...

 

[03SVTCOBRA10TH]

if you have a dial indicator you can use this,

Ratech 10006 - Ratech Pinion Depth Setting Tools - summitracing.com

Or just mic the pinion head depth from top of the pinion head to the flat bottom side, take a few measurements at different spots and average it. Then take that number and subtract it from 4.420" to get the tickness of shims needed. Then double check it with the tooth patten/ marking compound. That should get you very, very close.

 

[Kevin the Clean 1]

... I think we are getting closer to the cause of your clunking......

I sure hope so. No one has ever come up with a real/direct solution to this annoying problem yet...

 

[03SVTCOBRA10TH]

I sure hope so. No one has ever come up with a real/direct solution to this annoying problem yet...

This is one of the causes.

The problem is that the setting up of the diff, especially after a gear ratio change, affects the pinion depth. It must be corrected as well as back lash.

The other problem is that the diff center section is not soild or fixed to the car, it has rubber bushings. It really need soild aluminum mounts like the MM kit or bruces kit. Then you will notice increased NVH inside the car. To solve the problem you need Dyna mat or some other sound absorbing matierial. Then you need to soild mount the IRS sub frame to the car with the SHM aluminum bushings or the KB hard tail mount. Again NVH can be corrected with sound deadening.

Once the diff is set up correctly, the center section is hard mounted and the IRS subframe is hard mounted and the NVH is deadened, then you will have not rear end clunk. You may have noise if the wheel bearing or CV joint is shot, or is the suspension ismaking noise but not the rearend.

 

[Booksix]

Wow, Kevin, I see you feel strongly about this topic! LOL But I'm guessing you are referring more to the clunk from the slop in the IRS and not so much the clunking that I was experiencing.

But on that topic, I do have poly mounts everywhere on this unit (came installed when I bought it) and I'm hoping it'll reduced that specific clunk. I'm somewhat used to is because even my BMW Z3 Roadster has a bit of that same problem.

And one more question 03SVT, you say mic the pinion head to the "flat bottom side" and I was just a bit confused as to what you were referring to. The flat bottom side of what? Thanks!

 

[03SVTCOBRA10TH]

The pinion gear. The part that looks like a cone. From the top closest to the inside of the diff center section, to the flat spot that is on the gear just before it become the pinion shaft and goes out the hole to the pinion flange. It should be some where about 0.020" - 0.015" short of 4.420". But every pinion is different. Let us know what you get!!


I wish I could post pics on this site!!!! I've only been here since 2003!!!

 

[Booksix]

LOL, thanks! I know which one is the pinion (i'd be way over my head if i didn't) but I guess I'm not picturing it correctly. Are you saying you want me to actually measure just the gear portion of just the pinion gear or is this some kind of depth measurement with part of the center section as the reference point?

As for pics, I just use photobucket. It's free and all you have to do is paste the "IMG" codes into your thread...


edit: also, should I be ordering carrier and/or pinion shims? I'm assuming yes on the pinion shims but I think if backlash is adjusted by moving shims I should already have what I need....?

 

[03SVTCOBRA10TH]

No, I'm not trying to say you don't know what the pinion gear is, you are doing a great job so far, and I want you to be able to solve this problem and get back on the road. I guess I am just not making myself clear. I was answering your question in the above thread about which flat spot to measure to/ from. Let me see what I can do about some pics. What I want you to do is so simple, I guess my explaination was too confusing.

Try this:

http://www.modularfords.com/forums/showthread.php?p=1329785#post1329785

Yes, you will most likely be ok with carrier shims as you said the backlash was 0.004 and you want 0.006-0.008, so you can just remove shims and try to restack them to get the proper backlash, unless you only have a master set, which has only one shim per side. You will most likey need some pinion shims, but wait and see what you have on there first. If you need pinion shims I like this kit as you don't need a crush sleeve and therefore, can get away with out the dial inch pund torque wrench by not having to crush the crush sleeve and simply torque the pinion nut about 210ft/lbs.

86-08 SUPER SHIM KIT, 8.8" MISCFORD

 

[03SVTCOBRA10TH]

BTW, how did you post that pic of the ring gear pattern??? When I go to the advanced post option, there is nothing that lets me make an attachment for a pic.... weird!!

 

[Booksix]

Yeah, that always seems to happen with the simple stuff. Perhaps I'd get what you're saying if I'd pull the carrier. I should be all set to do so: I've marked the caps, checked backlash (just for curiosity purposes) and checked the initial wear pattern (also just out of curiosity). I think that's all I needed to do/check.

As for the pinion, I just ordered a torque wrench from a bicycle company. They sell them for working on carbon bike frames The brand is "Park" and it reads from 0-60 in/lbs. I wouldn't mind using a spacer or a crush sleeve but mainly, I wanted to see what this guy had the preload set at, to see if that was a contributing factor to my problem.

Ok, now, as for pics, I post all my pics on an external site. I use photobucket. Quick, easy, free sign up. Once you have your account you can upload your photos from your hard drive (or even from a phone - i have photobucket mobile on my iPhone). Once uploaded, simply hover your mouse over the photo and a box will pop up from which you can copy the link (I use the "IMG" tag link as this will display the photo in the thread rather than a link to it. Let me know if you have any problems!