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Thread: IRS center section install

  1. #1
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    IRS center section install

    Question about the center section fit in the frame. I was able to get the rear mounts to be more or less flush with the bushings. But the front mounts have a good size gap. Since the front sleeves are longer than the bushings, I am thinking this might be the design intent. If the nut is tightened up against the sleeve, is it OK that the center section isn’t touching the bushing itself?
    MK4 Roadster complete kit delivered 5/2/2025. Ford 390 FE engine with TKX and IRS.
    Engine build videos: https://www.youtube.com/playlist?lis...LfSTxcvVXT_BpP
    Roadster build videos: https://www.youtube.com/playlist?lis..._IjMh_XJLo0x29

  2. #2
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    This has been discussed a number of times and recently in this thread: https://thefactoryfiveforum.com/show...S-Differential. You can see my response (it's OK) and others who put in washers. Your choice.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread. Build 5: 35 Hot Rod Truck #138. Build Thread. Sold 11/9/2023. Build 6: Mk5 Roadster 30th Anniversary #11,258. Build Thread.

  3. #3
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    Thank you, your explanation makes a lot of sense. And glad to hear Factory Five agrees. If it were easy, I’d probably get some washers. But getting it in was not easy. Had two friends over and we had it in position within 10 minutes but spent the next hour trying to get all 4 bolts in. I’ve torqued them and marked them and will plan to check them after driving. Need to make a list of everything to check later.
    MK4 Roadster complete kit delivered 5/2/2025. Ford 390 FE engine with TKX and IRS.
    Engine build videos: https://www.youtube.com/playlist?lis...LfSTxcvVXT_BpP
    Roadster build videos: https://www.youtube.com/playlist?lis..._IjMh_XJLo0x29

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    Have been struggling with my IRS center section, but with a different problem! I positioned it solo with multiple ratchet straps, uneventfully. The polyurethane bushings are completely seated against the metal frame. I was able to squeeze the IRS center section between the front and rear bushings, but it is so tight, I cannot wiggle it to line up the rear threaded bolts. The bushings remain in good position and are not distored or damaged. The front section holes are roughly lined up with undersized, tapered 1/2 inch diameter rods in place. The 16mm bolts were not placed. The front section can be moved up and down with moderate pressure with the undersized/tapered rods in place. The rear section threaded holes are still approximately 1/2 inch above the mounting hole. The rear metal sleeves are not proud of the polyurethane bushings, but still in place within the poly bushings.

    I'm hesitant to use any force! Should I try to remove the metal sleeves and rear portion of the rear poly bushing? Have others had this problem? Any suggestions appreciated.

    Ed Z

  5. #5
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    Quote Originally Posted by Ejzajac View Post
    Have been struggling with my IRS center section, but with a different problem! I positioned it solo with multiple ratchet straps, uneventfully. The polyurethane bushings are completely seated against the metal frame. I was able to squeeze the IRS center section between the front and rear bushings, but it is so tight, I cannot wiggle it to line up the rear threaded bolts. The bushings remain in good position and are not distored or damaged. The front section holes are roughly lined up with undersized, tapered 1/2 inch diameter rods in place. The 16mm bolts were not placed. The front section can be moved up and down with moderate pressure with the undersized/tapered rods in place. The rear section threaded holes are still approximately 1/2 inch above the mounting hole. The rear metal sleeves are not proud of the polyurethane bushings, but still in place within the poly bushings.

    I'm hesitant to use any force! Should I try to remove the metal sleeves and rear portion of the rear poly bushing? Have others had this problem? Any suggestions appreciated.

    Ed Z
    I've done several of these now. What's worked for me every time is once the lump is in place, get the rear bolts started. Far enough in to hold and be firmly engaged in the threads (don't want to mess up that threaded back cover) but not tight or torqued down. Then use the tapered rods to align the front holes with the frame. Sounds like you made up some tapered pieces same as I've done. It may take some firm tapping (don't go crazy) but I've always been able to get the tapered bolts in far enough to line up both sides. Then take out one side, insert the bolt. Then the same for the other side. Good luck.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread. Build 5: 35 Hot Rod Truck #138. Build Thread. Sold 11/9/2023. Build 6: Mk5 Roadster 30th Anniversary #11,258. Build Thread.

  6. #6
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    Thanks Paul. My issue is that it is so snug between the bushings. I'll causiously pull out a rubber hammer for some gentle persuasion!

  7. #7
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    Quote Originally Posted by Ejzajac View Post
    Thanks Paul. My issue is that it is so snug between the bushings. I'll causiously pull out a rubber hammer for some gentle persuasion!
    I will only say, and you probably know this already, it's not easy to move. If you're anywhere near the holes to get the tapered bolt in there, that's going to move it when beating on it won't. Ask me how I know.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread. Build 5: 35 Hot Rod Truck #138. Build Thread. Sold 11/9/2023. Build 6: Mk5 Roadster 30th Anniversary #11,258. Build Thread.

  8. #8

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    Quote Originally Posted by Ejzajac View Post
    Thanks Paul. My issue is that it is so snug between the bushings. I'll causiously pull out a rubber hammer for some gentle persuasion!
    I put my first one in by myself with little issue. The second time I had my son and wife out to help balance it in the frame. And then it got stuck, no hands stuck. I'm like how is this possible? Told the family to go inside and I started all over again. Keep at it, you'll get it. As Paul said, it's a little heavy for a dead blow to move.
    MKIV Roadster - #9380 - Complete Kit - Delivered 7/17/18 - SOLD 5/2023
    Build Thread #1: https://thefactoryfiveforum.com/show...V-Build-Thread
    MKIV Roadster - #10827 - Complete Kit - Delivered 11/6/23 - Final Punch
    Build Thread #2: https://thefactoryfiveforum.com/show...Build-Thread-2

  9. #9
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    I did my fronts first and then the rears. Didn't have tapered pins. Rears were not lined up well at first but with ratchet pulleys (vs ratchet straps) I could do very small up and down movement until I could get one of the rears started. Once one was started it was easy to get the other lined up. Install was solo. Once it was under the car and straps hooked up, it took around 30 minutes to get it in place.

    Pat
    MK4 complete kit Nov 2024, Blueprint 347, TKX, Hyd clutch, IRS, 3.55, touring shocks, 17" wheels, 11.65 brakes, Build Thread

  10. #10
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    Gbranham was over one day and helped me put mine in my MK5.
    It fought us all the way but we finally got it in there.
    Without his help I'd probably still be trying to wrangle that thing in there !
    I know we had a couple of ratchet straps involved at one point.
    He said it was definitely tougher on my car than his MK4.

  11. #11
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    I did mine solo and it was a major PITA. I would get it soooo close and then it wouldn't budge at all. Don't like how hey made the rear bushings with the offset holes. I ended up taking the inner bushing that would make contact with the diff and put them against my belt sander and took about 1/16" off on both the front and rear bushing. That extra 1/8" of space was perfect. Still pretty tight but manageable.
    shaved bushing.jpg

  12. #12
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    Quote Originally Posted by 2nd2none View Post
    I did mine solo and it was a major PITA. I would get it soooo close and then it wouldn't budge at all. Don't like how hey made the rear bushings with the offset holes. I ended up taking the inner bushing that would make contact with the diff and put them against my belt sander and took about 1/16" off on both the front and rear bushing. That extra 1/8" of space was perfect. Still pretty tight but manageable.
    shaved bushing.jpg
    Thanks.
    I have the rear bolts temporaily threaded in safely, but had to remove the rear half of the rear bushings and the sleeves to get them started. The center section now sits ABOVE the FRONT bushing. Several clamps and ratchets straps have not allow clearance to position it.

    YOUR solution is the next step! Would have been so easy to just trim them up in the beginning.
    Hopefully, this will help others.

    Ed Z

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