The new 14mm fron IRS subframe mounting bolts...

[04HarleyF250]

thats interesting looking at the picture... Whoever took it decided to drop the entire brackets of the rear subframe (4 bolts) rather than taking out the bolt that interferes with a wider tire to drop just the subframe. I think that is the way it was intended to come out having just dropped mine and realizing ford did not design the "nutsert" or nut on the inside of the frame with a weak tab to be removed.

Brackets out of the car, you can easily get to the nut on the back.

 

[SNKBITN!]

Question for you guys. My buddy is going to instal the 14mm bolts on my car this weekend and he was looking at the irs and where the bolt goes and doesn't think his hand can fit in there to put the nut on the other side. He said he thinks he is going to need to drop the fuel tank. This doesn't sound right to me and wanted to see if you guys could give me detailed instructions on how to put these bolts in?

 

[Fastphil]

Don't push the bolt all the way through? I haven't installed mine yet, but he should be able to slip the nut and washer onto the bolt if the bolt hasn't been pushed all the way through yet.

 

[Taz]

Question for you guys. My buddy is going to instal the 14mm bolts on my car this weekend and he was looking at the irs and where the bolt goes and doesn't think his hand can fit in there to put the nut on the other side. He said he thinks he is going to need to drop the fuel tank. This doesn't sound right to me and wanted to see if you guys could give me detailed instructions on how to put these bolts in?

Are you sure he's looking at the right bolt??? The front one, right? As I recall, the nut is readily accessible for that bolt. The nut for the back bolt, which generally gets a "low profile" replacment bolt is welded to the chassis.

 

[LargeOrangeFont]

Question for you guys. My buddy is going to instal the 14mm bolts on my car this weekend and he was looking at the irs and where the bolt goes and doesn't think his hand can fit in there to put the nut on the other side. He said he thinks he is going to need to drop the fuel tank. This doesn't sound right to me and wanted to see if you guys could give me detailed instructions on how to put these bolts in?

He is looking at the wrong bolt. The bolts are in front of the rear wheels, outboard of the mufflers.

 

[forestgreen95gt]

I upgraded the rear to 14mm as well. The slot on rear subframe braket for the bolt to pass thru is 14mm in height but the factory had a 12mm bolt in there...not good. So I drilled and tapped the floating nut to accept the new 14mm bolt. Doing this together with solidly mounting the subframe and diff housing really made things a lot better. The only clunk I get now is from the slop in my transmission, and ring gear backlash. I heard some PTFE on the driveshaft yolk may help kill the clunks these cars make from the factory.

 

[Kevin the Clean 1]

forestgreen95gt,

Let me know what you find out. I hate the clunk on my 04...

 

[Fastphil]

So I just tried to do these bolts, and I have some input on how NOT to do it.

My main mistake was that I tried to do this with the rear of the car backed up onto ramps. Of course, this does not unload the subframe, making removal of the stock bolt a risky affair, and making installation of the new, bigger bolt just about impossible. Once the bolt is removed, the subframe would move up and completely misalign the holes.

Once I figured out this is not the way to do it, I came back and reread this thread. Jacking the car up and putting it on stands is the right (and probably the only) way to do this bolt swap.

I'm gonna take a fresh start at this tomorrow, but I have one question: Where is the best place to jack up the rear of the car? And where do I put the stands?

 

[Fastphil]

So I answered my own question today. I managed to get the bolts in, and it took about 2 hours total, working on the floor in my garage. That included getting the car up on stands, finding all the right tools, and taking my time. After all, I had all day to do this!

If you are replacing the stock bolts with 9/16” bolts, you will need the following tools:
Floor jack
Two jackstands
Breaker bar
Ratchet (the bigger the better)
18mm socket, preferably deep if you have one.
18mm wrench
21mm socket (deep)
22mm socket
Torque wrench
Hammer
New bolts, washers and Nylock nuts

Really, the hardest part is having to get out from under the car repeatedly to adjust the floor jack if the holes don’t line up when you’re trying to put the new bolt in. If you have help, this can easily be done in under an hour for both sides. It was interesting to see that there was still a visible gap between the bushing and the inside of the mounting point on the chassis. Maybe the sleeve was butting up already?

Step by step instructions aren’t even worth typing up. As a side note, someone mentioned to torque to 131 ft-lbs. I tried to get the bolts torqued, but I just couldn’t do it with the leverage that I could get. I probably got them to about 100 ft-lbs, which I would say is more than enough.

Impressions? The 9/16” bolt is much bigger than the stock one! The car is in the garage until at least the 1st of April, so I can’t say if it’s helped alleviate the clunks our IRS is known to have. In any case, you can’t go too far wrong for less than $10 and a couple hours of spare time!

 

[Fastphil]

I have a question about the REAR subframe bolts... on my car, they were the same 12mm bolts as on the front subframe mounts. Needless to say, there's a lot of play back at these mounting points also. Do we all have the same 12mm bolts in all four subframe mounting points?

 

[About2bite]

Good thread, lots of helpful info here

 

[Taz]

I have a question about the REAR subframe bolts... on my car, they were the same 12mm bolts as on the front subframe mounts. Needless to say, there's a lot of play back at these mounting points also. Do we all have the same 12mm bolts in all four subframe mounting points?

The 12mm bolts at the back of the IRS subframe shouldn't cause any play, as the rear mounting points are set up for 12mm.

The sleevs in the rear IRS bushings are 12mm and the nuts welded to the chassis for the rear IRS bolts to thread into are 12mm, so where is your play coming from?

 

[Fastphil]

The 12mm bolts at the back of the IRS subframe shouldn't cause any play, as the rear mounting points are set up for 12mm.

The sleevs in the rear IRS bushings are 12mm and the nuts welded to the chassis for the rear IRS bolts to thread into are 12mm, so where is your play coming from?

I can't say for sure that there even is any play, but the rear mounts looked suspiciously similar to the front mounts. After swapping the front bolts as discussed in this thread, I had to drop the rear of the IRS to swap the springs, and the bolts are the same as the fronts, and the sleeves look similar as well. The rear bolts showed signs of wear from movement, but the stock front bolts didn't.

I know that the nutsert would make it more difficult to install bigger bolts on the rear mounts, but I'm quite certain that the bolts that are in there are too small, just like the front ones are/were.

 

[redfiresvtsnake]

I just did mine today finally. The clunk went away. I had to loosen all 4 mounting bolts and move the irs subframe in place with a pry bar. Took about 30 min on a lift.

 

[Taz]

I can't say for sure that there even is any play, but the rear mounts looked suspiciously similar to the front mounts. After swapping the front bolts as discussed in this thread, I had to drop the rear of the IRS to swap the springs, and the bolts are the same as the fronts, and the sleeves look similar as well. The rear bolts showed signs of wear from movement, but the stock front bolts didn't.

I know that the nutsert would make it more difficult to install bigger bolts on the rear mounts, but I'm quite certain that the bolts that are in there are too small, just like the front ones are/were.

There's no movement back there with 12mm bolts in the rear. But it sounds like you're dead set on installing 14mm bolts in the back, so do it.

Just be aware going in that you'll need different bushings, because the sleeves in the ones you've got are too small for 14mm bolts to slide through.

 

[redfiresvtsnake]

There's no movement back there with 12mm bolts in the rear. But it sounds like you're dead set on installing 14mm bolts in the back, so do it.

Just be aware going in that you'll need different bushings, because the sleeves in the ones you've got are too small for 14mm bolts to slide through.

When I did my front mount bolts today I loosened up the rears so I could move the irs around as needed. With the 12mm bolts in the back loose, the rear mounts would NOT move in the bracket on the chassis, nor would the bolts move in the bushings. SO I can confirm you do not need the 14mm bolts in the rear, only the front.

 

[Fastphil]

OK, so maybe it's my imagination... anyways, I'm not the kind of guy who will go and re-engineer something from the fround up just because it's not perfect.

 

[redfiresvtsnake]

OK, so maybe it's my imagination... anyways, I'm not the kind of guy who will go and re-engineer something from the fround up just because it's not perfect.

I'd just change your front bolts. If you still have some clunk then, change your diff bushings. The heat breaks them down and allows the diff to move around and cause a clunk. Bruce's delrin kit is great.

 

[Predatorbird]

i just drove around town to three different hardware stores and no one carries a 9/16 locking nut. everyone has the bolt in stock, but not the nylon locking nut. :mj:

 

[Fastphil]

Check your Yellow Pages for specialty fastener stores. I found mine at a place called Bolts Plus. They might have a minimum purchase, for me it was $5, but the whole thing cost more than that. Best option is to call them up first, so you don't go driving around to a bunch of places for nothing. Some of them don't even sell to the public.