QUESTION: Who is using/has used a 3 bolt at the drag strip?

[CareerFiremanGuy]

ha, yes that's what I meant.

 

[DaveW012]

96Cobra mentioned drilling and adding the 4th bolt in post #19. I was curious about this too. Has anyone done it or know someone who has done it?

 

[I Bleed Ford Blue]

even if someone tried it, the extra bolt would break before the one that is there would. if you were to try that you would need to incorporate some kind of bushing that has similar flex to the already existing one.

 

[TMac]

There is both a 3 bolt and a 4 bolt differential cover. If you have a three-bolt cover you're out of luck. The 4 bolt cover is set up for the threaded bolt insert. The three bolt subframe however does not have the proper surround for the RH isolator/bushing and would require fabrication to fit one. It's certainly not just drilling a hole. Take a look at the pictures of both subframes and you'll see that it's not easy or a vendor would have already offered a solution.

 

[DaveW012]

Will Ford replace this in the near future or do you have to break the bolt to get the 4 bolt subframe?

 

[Cruising68]

Will Ford replace this in the near future or do you have to break the bolt to get the 4 bolt subframe?

Right now Ford will not replace a 3-bolt with a 4-bolt even if you break the 1 bolt. The Police version may be the exception. The lame solution from Ford is to replace the 1 bolt.

It appears to me that an average fabricator could find a bushing, drill out where the second bolt goes, and weld in the isolator. I have a 3 bolt subframe sitting waiting for recycling if anybody wants to give it a try. I was fortunate my diff cover had 2 bolt holes so it was somewhat easy to do the subframe swap.

 

[DaveW012]

What’s the cost of the 4 bolt subframe and diff cover with 2 bolt holes? Is it even available to buy these parts if you wanted to replace those yourself?

 

[96cobra]

even if someone tried it, the extra bolt would break before the one that is there would. if you were to try that you would need to incorporate some kind of bushing that has similar flex to the already existing one.

My suggestion was to use solid bushings to eliminate the flex and a bushing would not be needed for the fourth bolt. This would induce more vibration to the rest of the vehicle but shouldn't add more road noise.
If you are racing this vehicle any way to tighten it up is good.

 

[Cruising68]

What’s the cost of the 4 bolt subframe and diff cover with 2 bolt holes? Is it even available to buy these parts if you wanted to replace those yourself?

Can't speak for the diff cover but my 4-bolt subframe was $1600 delivered.

 

[DaveW012]

So your ST came with the diff cover with the 2nd bolt hole but single bolt hole in the subframe? I’ll have to check mine later. I installed harder durometer subframe bushings in my 17 Mustang GT and it helped with wheel hop dramatically. There was some slight vibration but nothing too bad. I would have done solid bushings but I was afraid there would be way too much vibration and noise while daily driving the car. Would you use a solid bushing just for the 1 bolt on the diff or for all of the subframe bolts as well? Is there any companies out there making solid bushings for the ST?

 

[Cruising68]

So your ST came with the diff cover with the 2nd bolt hole but single bolt hole in the subframe? I’ll have to check mine later. I installed harder durometer subframe bushings in my 17 Mustang GT and it helped with wheel hop dramatically. There was some slight vibration but nothing too bad. I would have done solid bushings but I was afraid there would be way too much vibration and noise while daily driving the car. Would you use a solid bushing just for the 1 bolt on the diff or for all of the subframe bolts as well? Is there any companies out there making solid bushings for the ST?

Correct, my diff cover had two bolt holes with only one of them used.

Regarding solid bushings, I'm not a big fan unless you are talking pure performance and not comfort. I put some poly bushings in my CTSV and while it handled great, daily driving was horrible and I swapped them back out.

 

[DaveW012]

Looks like there are few options for the 1 bolt. I wouldn’t mind adding the FenFab Diffy Stiffy or AWR diff mount but would Ford deny warranty work if they see it mounted?

 

[marksst]

I've been tuned for well over a year on my 21. No issues. I did hear that the state police have a bunch with failures. A friend told me 1/2 those in the state of MA had failures.


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[CareerFiremanGuy]

... would Ford deny warranty work if they see it mounted?

The only honest answer is they could deny your warranty, if they wanted to.

I've been tuned for well over a year on my 21. No issues. I did hear that the state police have a bunch with failures. A friend told me 1/2 those in the state of MA had failures.

So your '21 is a 1/3 bolt then?

Regarding MA PIU failures rates, 1/2 of them failing doesn't jive with overall reported failures. Plus, that many failures would be front page news just about everywhere.

 

[ZookaRoo]

The only honest answer is they could deny your warranty, if they wanted to.



So your '21 is a 1/3 bolt then?

Regarding MA PIU failures rates, 1/2 of them failing doesn't jive with overall reported failures. Plus, that many failures would be front page news just about everywhere.

True…also not all PIU are the 3.0l….most in my area are hybrid.

 

[3rd Rail]

Maybe it’s the hot rodder in me but has anyone tried solid mounts and drilling a hole for the fourth bolt? Works on the corvette IRS.

i wonder if that is what ford is ultimatly going to do, or just make a factory brace like awr?

 

[I Bleed Ford Blue]

Ford should just bring back the 4 bolt cradle. It was more than adequate for the even the heavily modded ST's. Then ford can quietly swap out the 3 bolt cradles for the 4 bolter over time.

 

[DaveW012]

Just wondering if you have the single bolt subframe but the 2 bolt diff cover is there a way to modify the subframe to add the 2nd bolt? Maybe open up that second hole and add a poly bushing? Has anyone thought of something like this?

 

[Cruising68]

Just wondering if you have the single bolt subframe but the 2 bolt diff cover is there a way to modify the subframe to add the 2nd bolt? Maybe open up that second hole and add a poly bushing? Has anyone thought of something like this?

Yes you can do this but it would require cutting the subframe and welding in a bushing. Somebody with limited fabrication and welding skills should be able to handle it.

 

[TMac]

Just wondering if you have the single bolt subframe but the 2 bolt diff cover is there a way to modify the subframe to add the 2nd bolt? Maybe open up that second hole and add a poly bushing? Has anyone thought of something like this?

It's possible, but it would have to be fairly precise. IMHO it wouldn't be something that could be done on the vehicle. At that point, you might just as well do the subframe. Or, stop worrying about something that may never happen. Even if it does, Ford will fix it. You can also get the AWR setup for peace of mind.