IRS Installation - A few Questions

[Gizmosrcool]

My friend Brandon dropped by and together with his oldest son, we installed the differential, and whew the hard and heavy part is complete. I have two questions.

The rear bolts to the differential pulled the sleeve slightly out of the front part of the bushing. Its seems the differential is slightly smaller than the space between the front mounts and the rear. Is this s concern? Should I try and shim it up? or is this normal?

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The toe arm has a ton of space. I have not tightened up at all, but there is a huge amount of space in there. I do not like smashing down and drawing the mounts in. Which would have to move quite a bit. Same question. Should I try and shim it up? OR is this normal?

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Thx Everyone. Tom

[CraigS]

I would fill all those spaces w/ washers. The bolt/nut would probably pull the toe arm closed but I don't like bending the mount ears unless they were obviously welded on at an angle.

[Gizmosrcool]

Hi Craig. Yeah. That is what I am thinking. For the diff. I’d like to get it forward and the sleeve not getting pulled out. I’ll try and lossen the back. See if it gets pulled forward. Then i can shim the back. For the toe arm. I’ll find some wider washers.

Thx. Tom

[Ted G]

My understanding is that the center section gap is needed and the sleeve needs movement in the poly bushing (although ever so slight). The sleeve dictates the gap.

Correct me if I am wrong.

[CraigS]

Ted I can't see a reason that the diff needs a gap but you may have a point on the toe link mount. It looks like there is a sleeve on the right side and it may be better to have a sleeve on the left vs a washer. But the good thing is that the rod end has no need to twist in normal suspension movement so a washer would be OK.

[Gizmosrcool]

Thx Ted and Craig. I will work on the toe arm setup and send a note to FF support and ask about the sleeve.

[TXJosh]

Hi Tom
I am just about to begin assembling the IRS on my MK IV. What did factory five support say and how did it ultimately work out for you?

Thank you
Josh

[Dave108]

I just installed my IRS last Saturday. I noticed the same thing. There is a gap between the frame and differential housing on both the front and rear bolts. The gap is about 1/8 inch wide. Is this common or should I disassemble one at a time and insert a washer in each space?

Dave

[BRRT]

I torqued down the rear bolts (that thread into the cover), closing that gap to zero. Then installed and torqued the front and let the gap go where it wanted.
I'm not sure stacking washers in there would make much difference. Easy enough to do.

[cv2065]

The front IRS mounting points and the longer sleeve in the bushing is rated as 'normal' to FFR. I had the same thing happen in my 2018 build, torqued it and let it ride. Never had any issues.

This time around, I also have about a 1/32nd or 1/16" gap between the right side rear IRS mount and frame after torquing to the 100 ft/lbs value. I loosened up the two front ears and re-tightened the rear mount and it closed the gap. Tightened the two fronts up again and the gap is back. Not sure if it's the bushing itself, but I sent a note to FFR asking if a washer is appropriate, but I'm thinking that the alignment may be 'normal' as well. There are many other builders that have the exact same issue, and I'm sure many more than those that never noticed it in the first place. You really have to be looking at it to see it.

[Mat1asBEV&ICE]

The gap for the trans seems normal. Lots of discussions about that. Just went through that too.

Regarding the toe arm, is that a washer in the front or the 1/4" spacer? Also, if you are doing a sway bar, now is the time to install the brackets that attach there.

[rvanstory]

I just installed my IRS this week. I ended up filling the gap on the front tow mounting ears of the pumpkin with a washer. If the gap is "normal", should I remove the washers? If they aren't needed, will they hurt if I leave them in?

[cv2065]

I just installed my IRS this week. I ended up filling the gap on the front tow mounting ears of the pumpkin with a washer. If the gap is "normal", should I remove the washers? If they aren't needed, will they hurt if I leave them in?

Here's FFR's response to the gap:

"That is consider normal for our install, and nothing needs to be done regarding it. You can proceed with the build."

Personally, I wouldn't see any harm if the washers are already in there. I most likely wouldn't take them back out.

[Dave108]

Thats good to know, thanks for the update.

[Cobra Depo]

I just installed the differential today and also noticed the gap. However, after taking the bolts back out and investigating the gap reveals the sleeve from the bushings. Adding a washer would push the sleeves out past the other side of the bushings. I believe best to assemble as the manual states and torque to spec.

[Grubester]

I installed my Mk4 IRS last year and I used washers. I believe the O.D. of the bushing is 5/8" and I used a washer that had a 5/8" I.D., so the washer was only taking up clearance w.r.t. the poly bushing and not affecting the sleeve-to-mounting-points of the frame.