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Thread: Irs differential bolts and grease

  1. #1
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    Irs differential bolts and grease

    Greetings,
    I have a few questions about the suspension on my MK4 Roadster. I installed the IRS center section two weekends ago and that all went reasonably well. My first question is about the torque spec on the four mounting bolts. I have revision 4Z of the complete kit assembly manual. On page 95 it says to torque all four bolts to 100 ft/lbs. However, later on in the actual torque specifications section around page 117 it says those four should be 129 ft/lbs. So basically it appears the manual contradicts itself. Any body know which is correct? Am I missing something?
    I am also seeking some tribal knowledge on greasing the front and rear control arms properly. I “think” the general theory is that the mounting bolts are intended to trap the metal inner sleeve against the chassis tabs. Thus the pivoting occurs when the black poly bushings rotate on the stationary sleeve. So that’s where grease needs to go, correct? The inside of the bushings are fluted which I guess is to create grease grooves. If I’m thinking about this correctly, I was going to go ahead and disassemble and “pack” the connections rather than try and just use a grease gun and hope it gets everywhere it needs to go. Obviously I intended to use the grease gun once assembled to confirm. Thoughts? Overkill? Thanks in advance.

  2. #2
    Indy Shu's Avatar
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    I just checked the Coupe specs and they've done the same thing on the torque specs. It's pretty easy to get to 100 and it's never going to move. I'd say split the difference and go to 115 or 120.
    You are correct on the grease. Thin layer on the bolt just to keep corrosion away, and what you can get on the bushings and grooves, which isn't much but at least it's all coated.
    I would have had this done a couple months ago if only I had the upper bushings, on POL.
    Last edited by Indy Shu; 01-25-2022 at 05:48 PM.
    John
    Gen 3 Coupe #334 received 11/4/21. Coyote, IRS, TKX, Wilwoods
    '02 GT donor, 4.6 sohc, Received #5488 on 5/29/06. 3-link, ps, pb. Hoosier Cobra member (Hoosiercobra.com)

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  4. #3
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    Agreed anywhere in the 100 - 129 ft lb range on the IRS diff mounting bolts is fine. They aren't going anywhere. Personally, I pump grease into the upper and lower control zerks before assembling them onto the chassis. You have to be a little careful not to spread the poly bushings in the process. But it confirms they're filled with grease. Plus makes them a bit easier to install. I grease them once a year as part of routine maintenance. Typically you'll see grease coming out between the poly bushings and the frame tabs.
    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.

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  6. #4
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    BTW I like to use a red synthetic grease. I don't understand why it happens but it seems to turn black w/ use. I like that because when I grease later, I pump until the grease coming out goes from black to red. That way I know I have greased enough.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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