BMR Cradle Bushing Install Questions

[phunk]

edit, I was able to repair my threads in the chassis... but I will not be able to use the delrin bushings.

I need to order a set of the urethane bushings. My cradle or chassis just is not true enough to get the bolts in. The holes dont line up well enough, so I need bushings with more give.

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[IvanCRF]

edit, I was able to repair my threads in the chassis... but I will not be able to use the delrin bushings.

I need to order a set of the urethane bushings. My cradle or chassis just is not true enough to get the bolts in. The holes dont line up well enough, so I need bushings with more give.

Since you already have the delrin bushings, would it be possible to bore out the delrin bushings just until you get a snug fit with the bolts? I don't have any of this stuff, but enjoy reading about your build.

 

[phunk]

I did a 5 minute investigation looking at the car here, and we can see there is clear evidence that something is fishy with my car.

Take a look at the 2 attached photos. Ignore the touchup paint I put on... the stock bushing shells leave indentations in the chassis where the paint/primer is gone, so I just threw some touchup paint on to reduce its likeliness of starting rust.

3 of the 4 cradle mounts, the indentation left by the stock bushing is concentric with the hole.

The 1 that gave me shit and got stripped out trying to get it in, the indentation left by the stock bushing is no where near concentric with the hole.

This doesnt make it easy to tell if its the cradle or car that is wrong, but there is a clear mismatch between my rear cradle and my chassis.

 

[phunk]

Since you already have the delrin bushings, would it be possible to bore out the delrin bushings just until you get a snug fit with the bolts? I don't have any of this stuff, but enjoy reading about your build.

Its a possibility but I would prefer to machine a new delrin bushing with an offset hole and then install it clocked in the correct direction.

 

[BMR Tech]

Some cars are like that.

What I can tell you confidently is, one of our cars here was worse than that - and we were able to get it to work.

It can be tricky, but the best way to do it is to manipulate the cradle in a fashion that allows you to get all 4 bolts threaded (started). Then, you run them up in a cross pattern a few threads at a time.

The cradles have enough flex, that they will conform perfectly fine when tightening, without issue.

 

[phunk]

OK I will give it one more shot with some buddies here to help. Perhaps I struggled more than necessary by going at it alone.

I did only put in a couple threads at a time, but with some more muscle perhaps we can influence it well enough to get that one started. In fact, since the threads already took a beating in my trouble spot, I might get that one in first and then work on the rest. Perhaps some ratchet straps flexing the cradle a little could help LOL

 

[BMR Tech]

Absolutely.

And do keep in mind, on the rear legs/mounts of the cradle....there are plates that extend aft, that have alignment holes that match closely to the chassis. So, you can use a BFB and pry it around a little to help. ;)

 

[phunk]

I was able to get it back in there myself! Very happy to have that all back together.

After using a tap on the one that got cross-threaded on the first shot, the new threads had a little more give to them (stock threads are extremely tight, even hard to turn the bolts in by hand when test fitting them).

The slight play from the tapped threads was actually all it needed to go back together like a breeze. Since I had anti-seize on all the bolts, I torqued to 115ft-lb rather than the recommended 129ft-lb... lubricated threads should be torqued slightly lower and the last thing I wanted was to tear out threads and have to screw around any more LOL. I will let it crush/settle the delrin for a day or two and then retorque and apply paint marks so I can keep an eye on it for a while.

One recommendation on the differential bushings install... It might be kind to make a note to run the front differential bushing bolts starting from the back and coming out the front of the cradle. The way shown in the photos would make it so that you could not pull the differential out without dropping the cradle again since the fuel tank is obstructing removal of the bolts in that direction.

I am extremely anxious the drive this car again now!

Thank you BMR Tech for your quick replies to my questions. Everything looks great in there and I look forward to future product releases of yours.

 

[BMR Tech]

Noted. I'll get with my instruction guy firs thing tomorrow.

 

[bmoore1488]

I was able to get it back in there myself! Very happy to have that all back together.

After using a tap on the one that got cross-threaded on the first shot, the new threads had a little more give to them (stock threads are extremely tight, even hard to turn the bolts in by hand when test fitting them).

The slight play from the tapped threads was actually all it needed to go back together like a breeze. Since I had anti-seize on all the bolts, I torqued to 115ft-lb rather than the recommended 129ft-lb... lubricated threads should be torqued slightly lower and the last thing I wanted was to tear out threads and have to screw around any more LOL. I will let it crush/settle the delrin for a day or two and then retorque and apply paint marks so I can keep an eye on it for a while.

One recommendation on the differential bushings install... It might be kind to make a note to run the front differential bushing bolts starting from the back and coming out the front of the cradle. The way shown in the photos would make it so that you could not pull the differential out without dropping the cradle again since the fuel tank is obstructing removal of the bolts in that direction.

I am extremely anxious the drive this car again now!

Thank you BMR Tech for your quick replies to my questions. Everything looks great in there and I look forward to future product releases of yours.

Do you remember what size the tap is, I am also having this issue with my car.

 

[phunk]

Do you remember what size the tap is, I am also having this issue with my car.

m14 x 2.0

this is the tap I used: http://www.mcmaster.com/#8305a42/=yuouan

I also used tapping fluid and took *very* special care that the tap was starting perpendicular and working into the existing threads rather than cutting its own threads. This will be very important to get right to keep the thread strength.

It only had to really re-cut the first thread or two since that was all that was really messed up. After that it only had slight effort to run through since it was opening up the rest of the rather tight threads.

 

[Jeff_oddo]

Hearing all these issues with the threads getting stripped is worrying me a little about trying to install this on my own. Lol

 

[ForTehNguyen]

thread it in by hand good first

 

[phunk]

Hearing all these issues with the threads getting stripped is worrying me a little about trying to install this on my own. Lol

Look at the photos I posted showing the misalignment that my cradle had and the indentations it left in the chassis.

Observing this before-hand would allow you the opportunity to address it before going in blind like I did. If prepared for it, you wouldn't have, or create, a problem.

Please note, that the threads did not get stripped. The issue is a result of the factory bolt's threads being very soft and tapered, allowing you to rather easily *cross* the first couple threads without it being too obvious until you go far enough to need to repair the entry thread.

I wouldnt fear it one bit, especially since its a known thing to watch out for now.

Let me just add that my Mustang is an entirely different beast now with all this IRS work done. The new-found confidence and stability it has under full throttle allows me to drive it much harder.

 

[Jeff_oddo]

You recommend using a decent amount of antisieze on the bolts?

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