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Thread: 8.8 questions

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    Default 8.8 questions

    Hey guys, next order of business (lol) is the 8.8. Going to look at one this weekend from the same guy I bought the 91 5.0 motor from(yes I bought it lol). Guy says it was rebuilt last year and it's a good rear end. I need to know from you guys what to check before I buy it( with in reason) and how to tell it's a 8.8. Dont have any reason to think the guy would try to pull a fast one but you never know. It's going into a 84

    Thanks

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    Moderator wraithracing's Avatar
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    The quickest and easiest way to tell if its an 8.8 is to look at the rear cover.

    Name:  ford axle.JPG
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    The 8.8 has straight sides at the axle tubes where the 7.5 is curved.

    After that check the pinion for excessive play. There should be a slight rocking back and forth when you turn the pinion, but if there is a large amount of play then most likely the bearings are shot and need to be rebuilt. Just look for leaks etc. and the overall condition of the rear end. If the owner will let you I would recommend pulling the cover and at least look inside. If he has nothing to hide shouldn't be a problem. 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:
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    1979 Pace Car now 5.0/5 speed
    1982 GT Awaiting Restoration
    1984 SVO Restoration in Progress
    1986 GT Wrecked by PO, but still want to save!

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    1984 Capri Returned to Bubble Back Glory
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    Quote Originally Posted by wraithracing View Post
    The quickest and easiest way to tell if its an 8.8 is to look at the rear cover.

    Name:  ford axle.JPG
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    The 8.8 has straight sides at the axle tubes where the 7.5 is curved.

    After that check the pinion for excessive play. There should be a slight rocking back and forth when you turn the pinion, but if there is a large amount of play then most likely the bearings are shot and need to be rebuilt. Just look for leaks etc. and the overall condition of the rear end. If the owner will let you I would recommend pulling the cover and at least look inside. If he has nothing to hide shouldn't be a problem. Good Luck!
    Thanks Trey

    I'm a complete newb so excuse the dumb question but how do I check the pinion for play? Also How do you tell what gearing is in it? He says it's got 3.73. Is there a way to tell on the outside?
    Last edited by Sask84gt; 04-13-2018 at 12:26 PM.

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  5. #5
    Moderator wraithracing's Avatar
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    Checking the pinion will be a bit difficult if you haven't done one before, but you can probably figure it out rather quickly.

    Essentially you will want to grab the pinion yoke and rotate it back and forth. There will be bit of slope which is backlash. That is normal, but there shouldn't be a lot. That is the trick when you haven't checked on before. If your current rear axle is working and not making noise, you might check your pinion first to give you and idea of what is normal or acceptable. If the 8.8 has more or a different amount of play, then that will most likely tell you that either the bearings are worn or possible ring and pinion are work and allowing more play than you want.

    Here is a video that shows excessive bearing movement and what you don't want. It will be harder to do the same check with the rear axle out of the car, but it gives you and idea. 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 Awaiting Restoration
    1984 SVO Restoration in Progress
    1986 GT Wrecked by PO, but still want to save!

    Current Capris:
    1982 Capri Roller
    1984 Capri Returned to Bubble Back Glory
    1983-84 Gloy Racing Trans Am/IMSA Body Parts
    1982 Capri RS 5.0 4spd T-tops

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    Hey guys, so I went and got the 8.8. Seems to be alright and not leaking any fluids. Forgot to check my 7.7 for play before I went. Checking the 8.8 it seems to move about a 1/4 inch either way before turning. Will that be alright? Guy said it was rebuilt last year with ford racing 3.73 gears. There definitely is more play than my 7.5. Also would it being a automatic determine the amount of play? Grabbing the yoke I cant move it up and down or side to sideName:  20180415_134005.jpg
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    Last edited by Sask84gt; 04-15-2018 at 02:47 PM.

  7. #7

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    Sorry to be a bearer of bad news, but that 8.8 sounds like it's worn (or busted) beyond worn out... with that much backlash found... and will need the full tear down, inspection, and redo... if actually rebuilt last year...
    Last edited by Walking-Tall; 04-15-2018 at 02:58 PM.
    Mike
    1986 Mustang convertible 3.8L ---> BUILD THREAD
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    Quote Originally Posted by Walking-Tall View Post
    Sorry to be a bearer of bad news, but that 8.8 sounds like it's worn (or busted) beyond worn out... with that much backlash found... and will need the full tear down, inspection, and redo... if actually rebuilt last year...
    Great

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    What's the best way to know for sure? Take cover off? He said its full of fluid.

  10. #10

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    The target gear backlash when an 8.8 is going together or back together is 0.008-0.014", measured from a tangent of the ring gear with a dial indicator. What exactly that translates to in degrees of rotation or approximate distance turned at the pinion flange is, I'm not sure, but it shouldn't be 1/4" each direction, or much or any more than what the clearance is inside between the ring and pinion gears. So, I'd call BS on it being rebuilt, or it was not assembled accurately with the correct pinion depth position with shims and/or the carrier's right/left position with locating shims... or bearings or spider gear wear or gear/axle splines worn badly... etc... hence the excessive backlash you're finding rotating the pinion flange.
    Last edited by Walking-Tall; 04-15-2018 at 04:03 PM. Reason: One too many zeroes, LOL...
    Mike
    1986 Mustang convertible 3.8L ---> BUILD THREAD
    1983 Mercury Cougar 3.8L LS
    1986 Ford Thunderbird 5.0L ELAN
    1966 Ford Fairlane sedan 200-6
    1966 Ford Fairlane GT (390ci 4spd)
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang Fastback
    1974 Pontiac Luxury LeMans

  11. #11

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    Quote Originally Posted by Sask84gt View Post
    What's the best way to know for sure? Take cover off? He said its full of fluid.
    Yes, cover off. Find out for sure where exactly all the slop is... then make adjustments/repairs/replacements from that sighted info... "He" said alotta stuff... they all do... it's sales... I've decided not to trust too many further than I can throw them anymore when it comes to purchasing things... the Windsor block in the shed here that's essentially a large paper weight was the last straw for me trusting the word of anybody else... it's 100% "buyer beware"...
    Last edited by Walking-Tall; 04-15-2018 at 04:02 PM.
    Mike
    1986 Mustang convertible 3.8L ---> BUILD THREAD
    1983 Mercury Cougar 3.8L LS
    1986 Ford Thunderbird 5.0L ELAN
    1966 Ford Fairlane sedan 200-6
    1966 Ford Fairlane GT (390ci 4spd)
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang Fastback
    1974 Pontiac Luxury LeMans

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    Quote Originally Posted by Walking-Tall View Post
    Yes, cover off. Find out for sure where exactly all the slop is... then make adjustments/repairs/replacements from that sighted info... "He" said alotta stuff... they all do... it's sales... I've decided not to trust too many further than I can throw them anymore when it comes to purchasing things... the Windsor block in the shed here that's essentially a large paper weight was the last straw for me trusting the word of anybody else... it's 100% "buyer beware"...
    Ok thanks, I got the rear end for 150 so I guess if it needs to be rebuild I did not spend much on it anyway.

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    Quote Originally Posted by wraithracing View Post
    Checking the pinion will be a bit difficult if you haven't done one before, but you can probably figure it out rather quickly.

    Essentially you will want to grab the pinion yoke and rotate it back and forth. There will be bit of slope which is backlash. That is normal, but there shouldn't be a lot. That is the trick when you haven't checked on before. If your current rear axle is working and not making noise, you might check your pinion first to give you and idea of what is normal or acceptable. If the 8.8 has more or a different amount of play, then that will most likely tell you that either the bearings are worn or possible ring and pinion are work and allowing more play than you want.

    Here is a video that shows excessive bearing movement and what you don't want. It will be harder to do the same check with the rear axle out of the car, but it gives you and idea. Good Luck!

    Well doing the same thing on the 8.8 there is no bearing movement at all. Wonder if they maybe just set the backlash to much?

  14. #14
    Moderator wraithracing's Avatar
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    I would say that 1/4" slop either direction on the pinion sounds a bit much to me, but I can't say the rear end is junk. The odds are it wasn't rebuild as stated and is just a standard tired 8.8.

    The video I linked to original showed excessive play in hopes of giving you and idea what you want to avoid. With that said, just because your 8.8 doesn't have type of movement doesn't guarantee anything either way.

    The best option at this point is to open up the rear cover, drain the fluid and take a look at what you have. Paying $150 for the setup isn't a bad price overall, the question is what will it take to make the rear end a good use-able setup?

    The setup may have too much backlash, it could be bearings going out, it could be a rear end that is just flat worn out. Inspection is the only way to tell. If you plan on doing it yourself, then I recommend doing some research via Google and You Tube to see what you are getting into. Rebuilding an 8.8 is not extremely difficult, but good tools, precise measurement, and attention to detail will determine how successful you are and how long the 8.8 will last.

    If you don't have the tools and equipment needed, Shop Press, Bearing/Race Driver Set, Torque Wrench both ft/lb and inch/lb, bearing pullers, and probably a few others then you might want to consider having it rebuilt professionally. Some of the tools can be rented at your local auto parts store, but not all of them. If you don't plan on rebuilding several rear ends over your lifetime then often the tools are not worth the cost of buying, therefore paying a Pro to rebuild the unit will be the cheaper and better option. 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 Awaiting Restoration
    1984 SVO Restoration in Progress
    1986 GT Wrecked by PO, but still want to save!

    Current Capris:
    1982 Capri Roller
    1984 Capri Returned to Bubble Back Glory
    1983-84 Gloy Racing Trans Am/IMSA Body Parts
    1982 Capri RS 5.0 4spd T-tops

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    Quote Originally Posted by wraithracing View Post
    I would say that 1/4" slop either direction on the pinion sounds a bit much to me, but I can't say the rear end is junk. The odds are it wasn't rebuild as stated and is just a standard tired 8.8.

    The video I linked to original showed excessive play in hopes of giving you and idea what you want to avoid. With that said, just because your 8.8 doesn't have type of movement doesn't guarantee anything either way.

    The best option at this point is to open up the rear cover, drain the fluid and take a look at what you have. Paying $150 for the setup isn't a bad price overall, the question is what will it take to make the rear end a good use-able setup?

    The setup may have too much backlash, it could be bearings going out, it could be a rear end that is just flat worn out. Inspection is the only way to tell. If you plan on doing it yourself, then I recommend doing some research via Google and You Tube to see what you are getting into. Rebuilding an 8.8 is not extremely difficult, but good tools, precise measurement, and attention to detail will determine how successful you are and how long the 8.8 will last.

    If you don't have the tools and equipment needed, Shop Press, Bearing/Race Driver Set, Torque Wrench both ft/lb and inch/lb, bearing pullers, and probably a few others then you might want to consider having it rebuilt professionally. Some of the tools can be rented at your local auto parts store, but not all of them. If you don't plan on rebuilding several rear ends over your lifetime then often the tools are not worth the cost of buying, therefore paying a Pro to rebuild the unit will be the cheaper and better option. Good Luck!
    Ok, I dont mind have to replace some stuff just dont want the rear end to be junk and not usable at all. Lol

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    This may sound like a stupid question but is there a difference between a 8.8 out of a automatic v8 vs a 8.8 out of a manual? So my car being being a manual will I have any problems putting in a 8.8 with 3.73 gears out of a automatic?

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    No.. Same differential

    And I would guess you're not checking the backlast 'properly'. You'd really need to open it and have a dial indicator to do so.
    1986 CHP SSP Coupe

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    Quote Originally Posted by Ourobos View Post
    No.. Same differential

    And I would guess you're not checking the backlast 'properly'. You'd really need to open it and have a dial indicator to do so.
    Ok thanks Ourobos

  19. #19

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    Trey recently tore apart my (severely?) punished and abused 8.8. It’s the one that took constant poundings from 1996 until 2016 across a span of several 1/4 mile passes, several hundred thousand miles and countless destroyed tires, motor mounts, transmissions, clutches, etc. It put up with me driving my car worse than if it would have gotten stolen for a very long while.

    I say this because that particular 8.8 had zero favors done for it other than an occasional fluid change. It wasn’t original to my worn out old pony but it only had 75K to my car’s 150K when I swapped it in. Fast forward to the downhill side of the 400K to 1/2 million mark and that 8.8 was only removed to put in an SN95 unit that had rear disc brakes. It wasn’t making noises although the limited slip clutches were long gone.

    Trey night have pictures of what the ring and pinion looked like. The pin for the spider gears was badly worn from one wheel wonder abuse after the clutches went out of the limited slip, that’s all I know for sure. I can only assume the axles looked beyond terrible too from countless high speed runs across several states at a crack.

    Now that I’ve set the table on what we’re talking about here.... my comment is this — I am absolutely certain my old 8.8 had less rotational play in it than that. I was messing with it after I took it out.

    If the housing is good, all is not lost. Pick your favorite ratio or inspect the gear set that’s there. Grab a crush sleeve eliminator and a carbon fiber clutch disc service kit and axle bearings and seals, etc. no time like the present to make an 8.8 new again.

    Consider northern racing brackets and 93cobra / 87-88 turbo coupe rear disc brakes while you are at it.

  20. #20

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    Everyone above has given solid advice. I would like to add to what they have said. Take the diff to an experienced builder with the proper tools. Unless you have access to the OTC/ Ford Rotunda pinion depth gauge you are gambling on a proper set up and are likely going to end up with noise or worse. $150 is not a bad price for a straight housing with axles and hopefully a good trac-lok that can packed with new clutches. Also as stated above proper back lash is .008 - .014 that is virtually no rotational play when filled with fluid. Only the slightest movement felt at the pinion flange. Then you also have to worry about bearing preload on the pinion and carrier bearings. That means not only do you have to be sure there is no play but also it cannot be too easy or too difficult to turn.
    Last edited by Lowetlx; 05-14-2018 at 10:58 PM.
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    FEP Senior Member 83gt351w's Avatar
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    Once you remove the cover and put a dial indicator on it, you’ll have a good idea what shape it’s in. I had a friend “rebuild” mine, and come to find out the backlash was way out of tolerance. I believe Ford recommends .008” - .012”. I think .014” would make it too noisy. Rebuilding them isn’t hard, just time consuming. Prepare to take the differential in and out several times when trying to get the proper backlash.

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    And I’ll add, when you go to crush the crush collar on the pinion, you better get a good nights rest first, wake up, eat your wheaties, and a protein shake. It takes about 400 ft lbs of torque to crush the d*%n thing.

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    Quote Originally Posted by 83gt351w View Post
    And I’ll add, when you go to crush the crush collar on the pinion, you better get a good nights rest first, wake up, eat your wheaties, and a protein shake. It takes about 400 ft lbs of torque to crush the d*%n thing.
    Good advice!
    A long 1/2" breaker bar and a 4' extension pipe will get 'er done. The first time that I did one I went slowly and kept checking to make sure that I didn't go too far as I was unsure of the process. Went well though.

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    So, like the rookie I am I actually realised that when I was trying to turn the pinion the lugs were moving to. So what I thought was backlash was actually the axles turning a bit. I had my son hold the lugs on the studs still and now there is very little play ( almost none )before engaging the wheels. Hope this makes sense as I'm not down with all the lingo yet.

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