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  1. #1
    More money than brains wjurls's Avatar
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    Homemade case spreader and holding fixture.

    So a couple weeks ago I finally got tired of hearing my rear end howling like a coyote so pulled my IRS to rebuild my rear diff and replace the IRS bushings. Didn't have the scratch at this time for Bruce's kit so just went with MM urethane. Still a marked improvement over stock. As for the rear diff I installed all new bearings and seals, new carbon fiber trac-loc from Tousley and FRPP 3.73 gears and Billetflow IRS brace. I made a custom holding fixture that I lagged bolted to my bench. The rig was made up of 1" square tubing and allowed the diff to hang down off my workbench.

    I then made two adaptor plates using 4" wide and 1/8" thick strap steel. I drilled two 7/16" holes 3.2" on center apart and 1/2" away from the edge. This allowed the plates to be bolted to the diffential case edge yet stay out of the way. I drilled two 1/2" holes centered in the other edge of the plate. The inner hole is to secure the differential to the holding fixture for torquing down carriers bolts and pinion nut. The outer hole is to attach my homemade case spreader.

    Here is a shot of the diff housing mounted with the plates in the fixture (in bolt torqueing mode).

    I made the spreader using 1" square tubing for the sides and 3/4" square for the top and bottom. The 3/4" fits inside the 1" nicely so I was able to notch out the ends of the 1" to accomodate the 3/4". I attached the corners using 7/16" clevis pins. I then drilled 1/2" holes in the middle of the sides. These holes have 1/2" clevis pins that insert into the outer holes of the holding plates. I fasioned the adjusting bolt using Racebronco's design.

    With spreader attached. When using the spreader the diff must float in the fixture. Notice no pins holding the diff to the frame here. Nevermind the c-clamp

    Because I was installing FRPP 3.73 gears I started with the stock pinion shim. I had to fool with the carrier shims back and forth for a while but finally got it dialed in with .011" backlash. Nice! A little shim makes a huge difference to BL!

    Don't have a picture but ran some marking grease on the gears and the pattern looked great. I got lucky on not having to fiddle with the pinion shim.

    I used a long piece of flat stock attached to the pinion flang that was just long enough to stop itself on the wall stud behind the workbench. This allowed me to torque the pinion nut with a breaker bar instead of a impact.

    It doesn't take much at all to go past the 29 inch pounds max of pre-load. My first attempt I was at 10In-lbs. Gave the nut maybe 3 degree's extra turn and the torque was then well over 30inches. I took it apart again and used a new crush sleeve and this time stopped at 20inch pounds.

    I also replaced my side bearings and seals.


    This set of tools from Harbor Freight is probably one of the best bang for the buck tools I have purchased from them. Makes race and seal installs a breeze. Pilot bearings too!

    My new gears are nice and quiet now and no more clunking from the rear as I replaced all diff and irs bushings and also replaced the front bolts with the 14MM ones. Before I started, my pinion had lost it's preload so had some obvious play back and forth and of course 0 preload torque. The ring gear had .018" of backlash which is really only .003 over max spec but my god the noise it made! I was expecting to find a ton of shavings when I opened the rear cover but everything actually looked really good. The only damage I found was some pitting on the main pinion bearing.
    2003 Sonic Blue Coupe
    K&N FIPK, Billetflow 2.93, Metco 4# lower, Stieg Stage IV port.SCT 2600 MAF,KB BAP, Centerforce DF, Fidanza FW, Fiore quadrant and adjuster, LDC cooling mod, LFP dual pass H/E, Canton bling, MRT catted H-pipe, Magnaflow Catback, SCT Xcal2 tuned by Greg at RET...

  2. #2
    Crazy SVT Poster fred50stang's Avatar
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    Nice fab work!

    I rebuilt the IRS in my car and did exactly what you did...minus the fancy case speader. Tryin to get the backlash and everything just right was a mutherF'r, it took me some hours to get it right. I didnt get it as tight as yours, it was around .015 b/l with mine. I wanted it a little tighter, but I was tired wrestling with it and called it good enough. To get my pinion tight, I used two bolts and wedged my pry bar between the bolts and put some leverage on it and after a couple 'slips'(-n-football), I got it. I wore safety glasses for good reason.

    Would have been nice to have a case spreader, is my point to that rant.

    Also, IMO I think its the pinion bearing that makes these rearends get noisy. Lot's of push and pull on that part, where as everything else is bolted tight and lots of 'meat' around the main caps.

  3. #3
    "Stock Car" 99cobra09's Avatar
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    Shit...i have to do mine again!! My lash is probably sky high, i guess ill have to try to make my own spreader.
    1999 Mustang SVT Cobra #1605
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  4. #4
    More money than brains wjurls's Avatar
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    Quote Originally Posted by 99cobra09 View Post
    Shit...i have to do mine again!! My lash is probably sky high, i guess ill have to try to make my own spreader.
    You getting a lot of noise or what?

  5. #5
    You really look at this?? sweet88gt's Avatar
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    I had asked questions about this very topic a few weeks back and didnt get any good info and sort of gave up. This will be nice to look at coming up soon.
    I too had plans of making my own case spreader but was told to take extreme care not to spread it beyond a desired limit. Never found out how far was too far. Did a search or gear setup limits for the aluminum case and never found anything that was different than the regular iron cases.
    Where did you get the specs that you used? I have a spare IRS that needs to get a set of gears and bushings. I have since misplaced a few parts and cant find the orignal pinion shim and bearing. Seems I am going to have my work cut out for me.
    Anyway thanks for the pics.
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  6. #6
    More money than brains wjurls's Avatar
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    The spec for the spread is .030" between the carrier bearings. This is kind of hard to measure with a regular caliper because the ring gear is in the way. I just spread the case untill it was about .040 close to the spreader screw. It doesn't take much at all to get that spread. My torque and backlash specs came from the ford manual.

  7. #7
    SVT God Nutty 5.0's Avatar
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    Nice write up and pics! Its a shame you wouldn't build a few more spreaders! I know someone that would buy one!
    2003 Redfire Cobra: Tuned by Jon Lund - SOLD!
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  8. #8
    More money than brains wjurls's Avatar
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    I may consider knocking out a few more. That prototype was made using Home Depot steel so it was expensive. I may go down to the steel supplier right down the street and see if I can get a good price break on 10' lengths. Home Depot doesn't carry 4" flat stock anyway. I got mine from some leftovers at work. I'll let you know if I do. I like to help support fellow garage wrenchers.

  9. #9
    Crazy SVT Poster fred50stang's Avatar
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    Quote Originally Posted by fred50stang View Post
    Nice fab work!


    Would have been nice to have a case spreader, is my point to that rant.

    Yes, I quoted myself. I am interested if you make another one...drop me a pm.

  10. #10
    More money than brains wjurls's Avatar
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    I guess I better get serious about this then LOL.

  11. #11
    SVT God Nutty 5.0's Avatar
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    Absolutely! Send me a PM if you're serious as it would make doing things much easier. I can front you some cash.

  12. #12
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    You made a mistake using crush sleeves... You need to put in solid spacers, they always loose thier preload.. It just seems to be one of the characteristics of the irs.

  13. #13
    "Stock Car" 99cobra09's Avatar
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    Quote Originally Posted by blackonblacksls View Post
    You made a mistake using crush sleeves... You need to put in solid spacers, they always loose thier preload.. It just seems to be one of the characteristics of the irs.
    Wow really!! I guess i have to use solid spacers next time i do my differential.

  14. #14
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    Seriously nice right up and info on tool design. Nice to see somebody take the time to help the guys out that don't have a clue! I really like the custom tool, very close to my ford tool that cost me ten times what yours did to make...should have made my own!

  15. #15
    Crazy SVT Poster zinc's Avatar
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    Sorry to be a newb about this but when setting the pinion preload you are crushing the sleeve how are you able to tell the bearing has contacted the race to know when to switch to an inch pound torque wrench?

    Also when setting the backlash are you measuring the movement of the ring gear with the pinion gear locked in place? If so what point are you measuring to in the picture above?

    Thanks

  16. #16
    More money than brains wjurls's Avatar
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    It's pretty easy. The pinion will flop around and have back and forth play untill the bearing is being contacted. Once the play is taken up it's time to go very slowly because the preload comes on fast. Just turn a couple degrees and then test with the torque wrench. If too low go one or two more degrees and test again.

  17. #17
    More money than brains wjurls's Avatar
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    Quote Originally Posted by zinc View Post
    Also when setting the backlash are you measuring the movement of the ring gear with the pinion gear locked in place? If so what point are you measuring to in the picture above?

    Thanks
    Yes that's exactly it. I have the dial indicator locked in a magnetic holding fixture which is secured magnetically to the holding fixture I fabbed up. With the pinion locked up (using some bar stock and c-clamps) I pulled the ring gear as far as I could away from the dial indicator body. While holding in this position I zero'd the indicator. Then I pushed the ring gear in the other direction towards the dial indicator body and the result is what you see in the pic. The plunger is making contact with one of the ring gears teeth.

  18. #18
    loud go pedal P49Y-CY's Avatar
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    nice job!

    i hope to someday become that advanced in my home garage

    (meantime i'll be lugging my diff over to unitrax lol)
    2004 svt cobra vert, competition orange, #0052, built 10/8/03 (original owner)
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    2003 svt cobra coupe, sonic blue, #, built 9/9/02
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  19. #19
    SVT God Nutty 5.0's Avatar
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    wjurls: Good call on the race installer. I picked one up at Harbor Freight as its on sale now.

  20. #20
    More money than brains wjurls's Avatar
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    It's a pretty nice set. I was a little worried about the aluminum handle but it seems to take a pretty good beating.

  21. #21
    Crazy SVT Poster viper82489's Avatar
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    Nice. Here's the spreader I made, I just used the two big holes in the case instead of making the plates. and you can kinda see the stand I made too.






  22. #22
    I want a $944 camera! no cigar's Avatar
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    Hey guys, sorry for the thread revial, but would any of you still happen to have the pictures that aren't showing up in this thread anymore?

    Thanks!
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  23. #23
    More money than brains wjurls's Avatar
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    I still see them in here... Which can't you see?

  24. #24
    SVT God SlowSVT's Avatar
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    Here is mine I just finished today.






  25. #25
    I want a $944 camera! no cigar's Avatar
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    Quote Originally Posted by wjurls View Post
    I still see them in here... Which can't you see?
    Sorry, I was browsing the thread at work... Looks like they were blocked lol.

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