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  1. #1

    Default Setting up a used 8.8

    My old 7.5 started making clunk clunk noises on sharp right turns. So I headed out to pick-n-pull and found a 96 vert with a traction loc 3:08 and $100 and some sweat later I headed home. Pulling it apart I pulled the too long 5 lug axles so that I could use my 4 lug axles from the 7.5 (I just mounted some nice 4 lug wheels and new 275/40/17 tires). I ordered new clutches and a ring & pinion install set along with motorsport 3:73 gears for it. I saw some of the ears were broken off a few clutch friction discs and some scraping on the inside of the diff cover! The horrah! Pulled out the carrier and popped off the ring gear, installed new clutch hardware (modified stack), and wiped off the pinion to pull it out. That's when I noticed it was a motorsport 4:10 set. When I pulled it out I found some of the clutch disc ears underneath it. Someone did something nasty to the original gear set I suspect. Anyhow I cleaned it all out and decided to go with the 3:73's but decided whomever installed the 4:10's likely didn't do it right (although they look perfectly fine).

    So now I'm starting from an unknown pinion shim thickness and began with .032" but it had a pattern on the driven side way out on the heel (outboard) side after setting .010" free play. I read since then the pinion depth should be 4.420" from the center of the ring gear but I didn't try to measure that before I began. Anyhow playing around and adding more shim to the pinion is moving the rub pattern inboard on the driven side. The coast side is rubbing on the toe (inboard end) of the ring gear teeth and adding more pinion shim thickness is helping it move towards the gear tooth center. I'm now up to .074" of pinion shim and have lost some of my free play which needs to be re-shimmed on the carrier bearings. This should also change the wear pattern somewhat from what I've read correct? Is .074" too much shim?

    Note: This is my first try at this although I understand the basics of to set up gears and bearings etc. I did torque the pinion and bearing caps to assure everything is where it should be (no pinion crush ring just yet though) and used a cheapo bearing dremel-relieved for a slip fit on the pinion for setting it all up.

    I am going to use a known thickness flat bar and depth mics to get a pinion depth measurement noting the bearing cap mount surface may not be at the center of the ring gear (I'll check for that and do the math to correct for it) just to do a sanity check at this point.

    Advice from those with experience is appreciated. They've actually figured it out already!

  2. #2

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    If the old 4.10’s didn’t make noise when you spun it over I would measure the shim stack that was there. It’s usualky a good starting point.

    beyond that I’ll defer to those who spend a lot more time turning wrenches than I’ve been able to in a long while.

  3. #3
    Moderator wraithracing's Avatar
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    As someone that has just gone thru this with several 8.8 rear ends and a Super Duty 10.5 rear end, all I will say is the proper tools and techniques make ALL the difference! Personally I hate setting up used gears from a different rear end. Reading the pattern can be challenging and frustrating. Went thru this with Erratic50's Saleen clone. Nothing I did would change the pattern the direction I needed. Ultimately we ended up installing new gears and I firmly believe that was the best option. Not saying that used gears can't be set up correctly and work just fine, plenty have done it and continue to. The biggest issue for me is/was with the car not driveable yet I had no way to verify how my setup might actually sound/work when done. All I could go by was the pattern.

    I had the same issue with chasing the pinion depth shim. Started with the one that came out of the rear axle, swapped to the one that came on the used gear, and then went both directions with no improvement in the pattern nor sound of the gears. Its possible the gears were toast since neither of us ever heard or used them ourselves and were purchased second hand. Anyway I literally have 3 or 4 days of assembly/disassembly, check/recheck, adding shims, removing shims, etc. with that gear set and ultimately we didn't use it.

    Once I realized that I was completely lost in regards to the setup of that rear end, I threw in the towel and bought the full setup tools for an 8.8 rear axle. Not suggesting that you have to, but in my case since I had Erratic50's, my 82 RS, my 82 GT, my buddies 86 SSP, buddies 83 RS, and several others that needed overall I felt the $450 tool would pay for itself in no time. Needless to say once I got the setup and measuring procedure down pat, the pinion shim and everything became a no brainer and one time deal. With the tool, I was able to get the pinion shim to +/- .01 range on the first try. I personally will never try setting up another without the kit.

    Just a couple of other things that I experienced trying to do my setup as you have done. The honed out pinion bearing, I saw as much as .05 difference between using the slip on bearing and actual pressed on bearing. That alone caused me tons of frustration. I will never use the slip fit bearing setup again personally. Might just be me, but not worth the trouble. Next item is ALWAYS install your setup for the pinion with a crush sleeve installed. Using the original crush sleeve is a great place to start. As long as you don't use an impact on the pinion you won't have any issues with additional crush. After talking to a friend of a friend that has done hundreds of 8.8's he admitted that often he just uses the original crush sleeve with the new bearings as long as the rear end didn't suffer major damage or issues. Start with the OEM shims for your carrier when possible, especially if running the same gear ratio as before. If installing used gears, the coast side of the pattern is more important than the drive side and will yield a more correct setup in most cases. Good Luck!
    Last edited by wraithracing; 10-11-2019 at 08:52 AM.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Ongoing RestoModification
    1984 SVO Awaiting Restoration
    1986 GT Wrecked by PO, but still want to save!

    Current Capris:
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  4. #4
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    What is the tool or tools that you purchased to make it so much easier? Rear gears are one area of a car I've never dabbled in. I've always had other people set them up for me. I'm considering rebuilding the 8.8" rear end I have for my LTD, but I keep going back and forth.
    '89 XR-7 5 Speed
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  5. #5
    Moderator wraithracing's Avatar
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    The tool was a Deluxe Pinion Depth Checker. I don't remember exactly where I purchased it right now, but here is the same brand and tool that I purchased. The price was around $450+/- not a cheap tool, but I tried all the other cheap options and they weren't working for me. Definitely not a single use purchase IMHO, but since I have several Foxes with 8.8, a couple of 9", and as I stated my 10.5 in my Super Duty. This kit will do them all. Makes it a bit more complicated to set it up depending on which rear end you are using, but once you do and understand how to read the tool and use the information it is AWESOME!! Have already setup 3 rear ends with it and the setup time has gone from several hours per rear end to the last one I had done in just over an hour from measurement of the pinion depth until the back lash was set and the R&P was installed and ready for gear oil.

    https://www.toolsid.com/td-machine-p...saAgXCEALw_wcB
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Ongoing RestoModification
    1984 SVO Awaiting Restoration
    1986 GT Wrecked by PO, but still want to save!

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Underway
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  6. #6

    Default

    Thanks Wraith. I didn't make it clear the 3:73's are new Ford Racing parts which are the ones I'm installing. The 4:10's are the used pieces.

    I'll start over with measuring pinion depth using the old crush washer as you suggest. It is supposed to be 4.420" from the BOTTOM flat surface of the pinion (where any shims you use would touch the gear) to the center of the ring gear. There are a few places that sell tools to measure this that first find out if the bearing saddles are centered on the ring gear or not and then measure from the flat spots on the bearing saddle (where the tapped hole is) to the top of the pinion. Then you must measure the top to bottom thickness of the pinion gear (shim interface surface to the top of the gear where the gear ratio numbers etc. are cast). Add that distance to the saddle to gear top distance while adding or subtracting any offset for the saddle not being centered on the ring gear. This should add up to a number near but likely lower than 4.420". Add pinion shims to get as close to 4.420" and you are there.

    Wrath - I assume your variances stated in your post were .001" and .005" (thousanths) rather than .01" and .05" (hundreths)? This means the use of a slip fit bearing can throw off pinion depth by up to 5 thousanths of an inch. Since the top and bottom edges of the inner sleeve of the bearing is not modified (only the I.D. is) it is hard for me to imagine this making any difference but your experience says otherwise. Perhaps it is all in the deeper seating of the un-modified bearing on the pinion as it is pressed in place versus the seating supplied only by bearing pre-load only on the slip fit bearing. Using only bearing pre-load would not give you as much pinion depth as with pressing on a bearing first and then using proper pre-load. Your info will allow me to know to do this properly.

    If I had faith the 4:10's were properly installed I would use the shims beneath the pinion as a start. The carrier shims were stock Ford cast units with no additions so I assumed someone simply swapped in the shims from stock 3:08's when the 4:10's were put in. Since I found clutch damage etc. inside the case I was very concerned somebody had no clue about what they were doing and decided I would try and do it right (if I can that is). I'll start over and measure pinion depth and shim accordingly.

    Are you using the Ford Pinion Depth Gage Set P/N 205-S127 (T79P-4020-A) or something like the Pro-Form tool?

    Thanks again for your advice and experience.
    Last edited by Solow302; 10-11-2019 at 08:19 PM.

  7. #7
    Moderator wraithracing's Avatar
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    Sorry Yes I missed an extra Zero.

    I know others have used the slip fit bearing trick and I tried it on two different setups and had the same issues on both. Maybe its me, but bottom line is I won't use it again. I tried using the Ratech 8.8 Pinion Depth setting tool, again probably me, but I was not happy with my results.

    What I used and will use from this day forward is the kit I linked to in the post above. Again not a single use tool, but since I have several to setup over the coming years and I don't like paying others to do this for me, the tool will pay for itself if it hasn't already. Good Luck!
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Ongoing RestoModification
    1984 SVO Awaiting Restoration
    1986 GT Wrecked by PO, but still want to save!

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Underway
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  8. #8

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    I just finished doing some serious measuring of the pinion and calculating pinion depth. Turns out the thickness of the Ford Racing 3:73 pinion from the bearing race surface to the top of the gear varies quite a bit (about 0.020" or so). Measuring that with a set of calipers drove me nuts because each gear tooth seemed to have a different measurement (but on each separate tooth the values repeated every time). One was marked with a scratch or maybe a tool mark and in the end I used it to do all my measurements from. After positioning a straight flat bar of uniform thickness (measured) across the carrier bearing surface in the housing I used a depth gage to measure to the top of the marked pinion gear tooth. I double checked it with a digital caliper as well. I measured the carrier race diameter and the housing race radius machined in the housing and it came out within .001" of being half the race diameter (no math adjustments needed). After doing all the math it came out needing a 0.021" shim to get the 4.420" pinion depth (BTW the Ford installation pdf says pinion shims go from .010" - .038" - was that a hint?). Now it's time to check backlash and see what sort of pattern I have.......
    Last edited by Solow302; 10-13-2019 at 06:02 PM.

  9. #9

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    Backlash was .021" so I corrected the carrier shims and brought it to .010". Pattern looked pretty good (much thicker contact patch than with the .060"+ pinon shim) but still a bit toward the outside of the teeth on driven side and about right on the coast side. I'll add maybe .003" - .005" more pinion shim and I should be good.

    Moral of the story - measure pinion depth (in same spot if the gear thickness varies) before you start if you don't have a factory shim to go by.

  10. #10

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    Some great info from Wraith! Have used the interferance fit on the bearings to set pinion shim. Using a used crush collar is a good starting point. On the front pinion is a plus or minus on it. This is to let the installer know how much material was machined off the pinion.
    If im not mistaken .007-.013 is the amount of backlash between the gearset. Myself … I shoot for .009. I also use the Raetech Carrier shim holder. It makes life easier to preload the carrier bearings.
    Not a task that most would attempt! Good luck!

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