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Thread: Irs clunk

  1. #1
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    Irs clunk

    I have a little over 200 miles on the roadster and really enjoying it, I do have two issues I am trying to work through. One being a clunk when I shift gears or get off and then back on the throttle. When I raise the car and turn the tire the clunk is coming from the center section for sure, maybe too much backlash. Does anyone else's do this?
    Second issue is with the coyote which takes a while to fire once it hasn't run for a while. I am thinking checkvalve in the fuel pump? Thanks in advance for the help.

  2. #2
    Senior Member BadAsp427's Avatar
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    The clunk.... perhaps this is too obvious or too lucky... is it your U-Joint(s) Too lucky ie it's a whole lot easier and cheaper to fix the U-joint than the rear end...

    Mk4 20th Anniversary #8690 ( #8 of 20 ) Purchased 8/18/18 Started 8/19/18 First Start 11-1-18
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    I checked out the u-joints and the sound is definitely in the center section. The yoke turns a lot before it actually turns the wheel.

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    edwardb's Avatar
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    Assume you're talking about the newer 2015+ IRS? (Would be helpful to have your build details in the sig line like you've probably seen in other forum member's posts.) Mine doesn't make any noise and I don't recall this ever being posted for the newer design. The yoke does turn some before the wheels which is normal. Whether that's the "a lot" you're describing is hard to say. You might even hear the ring and pinion a little when doing this if you have it up in the air and are close to it. But that doesn't necessarily mean that's the source of the clunk. What is the background of your center section? New or ??? Have you checked the bolts on the yoke adapter? Also driveshaft U-joint?

    For the Coyote start, again depends on your definition of slow start. Can you describe further? Mine starts within a second or two basically every time. Even after it's sat for a while. I don't know about a check valve in the fuel pump, but you should be getting fuel pressure at the regulator and fuel rails almost immediately once the fuel pump starts. The system gets pressurized very quickly. Do you have a gauge on your regulator? You should see it jump to full pressure (55 PSI) almost immediately when the key is turned from off to on, e.g. before even going to the start position. If so, the fuel system isn't likely the problem.
    Last edited by edwardb; 11-05-2018 at 08:57 AM.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014.
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  5. #5

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    FFR sent out shorter drive shaft bolts to the IRS users because the originals were too long. Perhaps your bolts are bottomed out and not actually clamping the driveshaft?
    Mike

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    Senior Member CraigS's Avatar
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    Quote Originally Posted by michael everson View Post
    FFR sent out shorter drive shaft bolts to the IRS users because the originals were too long. Perhaps your bolts are bottomed out and not actually clamping the driveshaft?
    Mike
    Were those the bolts that attach the adapter to the diff flange, or the bolts that attach the drive shaft to the adapter?
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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    Try stopping at "key on" for a second before going to start and see if the Coyote likes that.
    20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud.

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    Senior Member Just puttering's Avatar
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    I hope this is a totaly stupid question, but there is alot of talk of diffs with or without oil when people receive them.

    Is the oil level good in the diff?

    Is the clunk new or getting worse or there from the start?
    Last edited by Just puttering; 11-05-2018 at 08:54 AM.
    Mk3.1 347 AFR 205cc Race Heads EFI siemens deca 60lb injectors MSD 6AL ignition Vortech V-3 3 Link PS/PB

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    edwardb's Avatar
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    Quote Originally Posted by CraigS View Post
    Were those the bolts that attach the adapter to the diff flange, or the bolts that attach the drive shaft to the adapter?
    In my case with #8674, it was the adapter to diff flange bolts that bottomed out before fully clamping the adapter. It wasn't a lot. As I recall, I just ground the ends off slightly and it was OK. But if left that way, certainly could cause the clunk. My Coupe kit came with shorter bolts.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014.
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    Senior Member CraigS's Avatar
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    Quote Originally Posted by edwardb View Post
    In my case with #8674, it was the adapter to diff flange bolts that bottomed out before fully clamping the adapter. It wasn't a lot. As I recall, I just ground the ends off slightly and it was OK. But if left that way, certainly could cause the clunk. My Coupe kit came with shorter bolts.
    Thank you!
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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    I have noticed more of a clicking when I change torque direction on the driveshaft. When I downshift and let off the clutch immediately after being on power.

    For me the issue is the end flange on the driveshaft (end connecting to the rear adapter) is not holding. It's not loose. The holes in the flange are a little larger than the threads of the bolt. If you hold your foot on the brakes and let out the clutch a little in first then go to reverse do the same thing, you can force the noise.

    Another IRS noise I had in the first 200 miles was the suspension bolts to adjust the A arme lengths were loose. the large lock nuts had loosened since the alignment. I had to tighten both sides in several spots after about 200 miles.

  12. #12
    edwardb's Avatar
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    Quote Originally Posted by forcefed1 View Post
    I have noticed more of a clicking when I change torque direction on the driveshaft. When I downshift and let off the clutch immediately after being on power.

    For me the issue is the end flange on the driveshaft (end connecting to the rear adapter) is not holding. It's not loose. The holes in the flange are a little larger than the threads of the bolt. If you hold your foot on the brakes and let out the clutch a little in first then go to reverse do the same thing, you can force the noise.
    First I've heard of that and haven't heard/seen anything like that on mine. Hard to imagine that the driveshaft is moving on the adapter with the bolts tightened to the specified 80 ft-lbs. Even if the holes are slightly oversize. That's a lot of clamping pressure. Any chance they're bottomed out in the holes?

    Quote Originally Posted by forcefed1 View Post
    Another IRS noise I had in the first 200 miles was the suspension bolts to adjust the A arm lengths were loose. the large lock nuts had loosened since the alignment. I had to tighten both sides in several spots after about 200 miles.
    Factory Five says to use red Loctite on those adjustment nuts. Also the ones on the toe arms. Unfortunately it's in a tech upgrade instruction sheet issued not long after the newer IRS was released. Haven't seen it mentioned in the regular instructions. I did that plus added paint stripe witness marks to confirm they hadn't moved when doing PM.
    Last edited by edwardb; 11-05-2018 at 07:02 PM.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014.
    Build 2: Mk4 Roadster #7750. Sold 04/10/2017. #7750 Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. 03 of 20. 2015 crate Coyote, 2015 IRS. Legal 04/18/2017. #8674 Build Thread
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    Sorry about the lack of detail. It's a brand new center section straight from ford via factory five, 3.55 gears and the limited slip. The fluid is right at the fill plug but the clunk actually sounds like it has no fluid. I checked the u-joints and the coupler to the yoke and it all looks good, I did use the shorter bolts as the other ones did bottom out. I have a video which I sent to factory five but haven't heard back yet. I have actually set up many gear sets over the years, dana30, dana44, Amc 20 and the ford 9 inch but have never heard a noise like this. Factory five told me the clutches need to break in and the noise will diminish after 500 miles or so but it seems to be getting louder. I could take it apart but I figure it should be under a ford warranty. I don't know how to post video on this site or I would. The fuel pump issue is for another post and time, one issue at a time. Thanks for all the help.

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    Senior Member Just puttering's Avatar
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    Quote Originally Posted by Rsnake View Post
    Factory five told me the clutches need to break in and the noise will diminish after 500 miles or so but it seems to be getting louder. I could take it apart but I figure it should be under a ford warranty..
    I could see that if it was clunking going around a corner, i dont think you could get a posi to clunk by hand. Just a thought, if you lift just one tire, it should be solid trying to turn the one in the air with the other on the ground. You may be able to judge the slack in the backlash compared to the gears in the posi.

    Can a person go to a dealership for warranty on these diffs? They may be able to look at it in the car, and then if need be, you could pull it for them to fix? If not, you will save your self not having to pull it out for them to look at!

    Talk to ford soon, if you keep driving it they may not warranty it???
    Mk3.1 347 AFR 205cc Race Heads EFI siemens deca 60lb injectors MSD 6AL ignition Vortech V-3 3 Link PS/PB

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    edwardb's Avatar
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    Quote Originally Posted by Just puttering View Post
    Can a person go to a dealership for warranty on these diffs? They may be able to look at it in the car, and then if need be, you could pull it for them to fix? If not, you will save your self not having to pull it out for them to look at!

    Talk to ford soon, if you keep driving it they may not warranty it???
    Interesting question. Just did a little looking and the news doesn't seem great. From the Ford Performance website: "All Ford Performance Parts are aftermarket parts. Ford Performance Parts are not Genuine Ford Parts or Accessories...." and "Ford Performance Parts Parts are sold "as is" with no warranty. A Limited Warranty is available for some select parts..." Crate engines (including Coyote's fortunately) are listed, but the center section is listed as not having a warranty. I doubt any Ford Performance part, including those with a warranty, would be serviced at a local Ford dealer. Seems the first step in any case would be to call Ford Performance.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014.
    Build 2: Mk4 Roadster #7750. Sold 04/10/2017. #7750 Build Thread
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    One of the first checks I would do is see if the pinion/flange will move in and out of the carrier housing.
    I won't go into the causes, but the easiest is a loose nut holding the flange on. Maybe you can compare yours to someone else's.
    20th Anniversary Mk IV, A50XS Coyote, TKO 600, Trunk Drop Box, Trunk Battery Box, Cubby Hole, Seat Heaters, Radiator hanger and shroud.

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    Oh well on the warranty. I guess I will dig into it. The first step is the check the pinion nut. I am sure ford uses a crush sleeve which I always eliminate when I build a rear diff, yes it's harder to setup without a crush sleeve/washer but I never have to worry about it. You guys are awesome. I will report back later tomorrow after removing driveshaft.

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    So after the last post I figured I might as well go out and check the pinion nut. It looks good and no slop in yoke.
    I have exactly 1/4" movement in the yoke. Pics attached. So I crawled under my jeep which has been rock crawled hard with an amc20 I built years ago and the play in the yoke is 4 times worse but it's quiet. When you rotate it it takes up the backlash and is silent whereas the roadster sounds like it has no gear oil when it takes up the backlash.image.jpeg
    image.jpeg

  19. #19
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    Quote Originally Posted by Rsnake View Post
    SFactory five told me the clutches need to break in and the noise will diminish after 500 miles or so but it seems to be getting louder.
    Please note that the 2015+ IRS does not use clutches.
    MK4 #9191, Gen 3 Coyote, T56, 2015+ IRS, ABS, 12.88 Wilwood's, FFR Tubular Front LCA's, FFR Spindles

  20. #20
    edwardb's Avatar
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    Quote Originally Posted by dhuff View Post
    Please note that the 2015+ IRS does not use clutches.
    Curious what you mean by that. The majority of the 2015+ IRS center sections use the typical Ford Trac-Lok system with mechanical clutch packs made up of multiple disks in a carrier. The only stock exception is the 3.73 diff sold with the a gear type Torsen setup. Other ratios can be retrofitted to the Torsen setup, but it's a custom job. The OP describes a new 3.55 diff from Factory Five. That would be the usual Ford Performance version with the clutch pack Trac-Lok.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014.
    Build 2: Mk4 Roadster #7750. Sold 04/10/2017. #7750 Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. 03 of 20. 2015 crate Coyote, 2015 IRS. Legal 04/18/2017. #8674 Build Thread
    Build 4: Gen 3 Type 65 Coupe #59. Gen 3 crate Coyote. Delivered 12/2/2017. #59 Coupe Build Thread

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    Quote Originally Posted by edwardb View Post
    First I've heard of that and haven't heard/seen anything like that on mine. Hard to imagine that the driveshaft is moving on the adapter with the bolts tightened to the specified 80 ft-lbs. Even if the holes are slightly oversize. That's a lot of clamping pressure. Any chance they're bottomed out in the holes?
    I agree, it sounds to me like forcefed1 might be bottoming out in the holes. Sound similar to my issue. Seemed tight enough at first, but after a few hundred miles it became more pronounced with wear. Not sure it helps the OP, but just in case here is my link on the issue that I had.
    https://thefactoryfiveforum.com/show...s-bottomed-out

  22. #22
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    Quote Originally Posted by edwardb View Post
    Curious what you mean by that. The majority of the 2015+ IRS center sections use the typical Ford Trac-Lok system with mechanical clutch packs made up of multiple disks in a carrier. The only stock exception is the 3.73 diff sold with the a gear type Torsen setup. Other ratios can be retrofitted to the Torsen setup, but it's a custom job. The OP describes a new 3.55 diff from Factory Five. That would be the usual Ford Performance version with the clutch pack Trac-Lok.
    Oops, sorry about that, i purchased a used track pac differential, a 3.73 Torsen so i had that differential on the brain.
    MK4 #9191, Gen 3 Coyote, T56, 2015+ IRS, ABS, 12.88 Wilwood's, FFR Tubular Front LCA's, FFR Spindles

  23. #23
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    Clunk update.. I spoke with a shop that specializes in late model mustang performance and he said the clunk is very common with the new super 8.8 differential and it's because ford changed the fluid requirements from 75-140 to a 75-90 weight for fuel economy. So I purchased 2 qts of 80-140 gl-5 gear oil and changed the oil this morning. The factory oil I drained from the diff was thin, much thinner than the gear oil going in. No more clunk! One issue fixed now on to the next.

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