Broken diff bolt problem after problem

[Winter.M3]

I’ve had bad wheel hop for a while. I broke my differential mount clean in half once, 3 hours from home…

About 3 weeks later my diff bolt broke, it’s was one in the back. Took it to a shop and they had it replaced. Now, about two months later, my diff bolt broke AGAIN. I went and tried to replace my subframe with new diff and subframe bushings (which I was way over my head about, I took half of it apart and put it back together). Said screw it but I did check the diff bolt out. Is there any easy-ish way to remove the nut side of the bolt?

Also why is this such a big problem for me? I do a rolling launch here and there, I’m not doing digs or racing/tracking. Hopefully the poly bushings help out the wheel wobble and stabilize the subframe and diff.

And I called a shop and they quoted 6k, with a new subframe. I sourced a used subframe and had a friend install the bushings on it at hyundai for free. So he said the labor would be 2-3k. Does this sound right? It’s delta V in Richmond VA. If there’s a better shop let me know. “The shop” in Richmond said it wasn’t something they’d get in to…

I’m still driving the car, it’s my only car, and it’s fine. Subframes already bent, and as long as I don’t hit the throttle, gas SLIGHTLY too hard or shift poorly it doesn’t move the subframe/diff at all. I can feel a big knock if it moves.

[North.E92]

Are you mt? Wheel hop and any kind of hard shifting/launching will kill your diff bolt solution is to upgrade to stiffer bushings but if your subframe is already bent the bolt might still snap

[pbonsalb]

I did not change the subframe but I did DIY the diff and subframe bushings. I was able to lower enough for that work without removing it entirely. You will have to drop it. Disconnect the short brake lines that are enough trouble many don’t replace when doing braided lines, the diff input and axle stubs, and suspension arms and all brake/sensor/diff wiring. Maybe use a 2 stage trans Jack with supporting brackets or a friend or 2 to lower the subframe with diff. Then swap and reinstall. Not easy but not $2-3k if you DIY.

[Scrippy]

Is it the launching or are you hitting your diff on shit? There's some pretty bad scrapes on the bottom of your diff fins. I'm not sure how that happened because I'm pretty low myself out here in the shitty Cali roads and I have zero scratches on my diff. I also have 240,XXX miles. Do you Jack the car up by the diff? I understand there is a valid spot in front of the fins but I still would never do that.

[amrazM]

Originally Posted by Winter.M3

I’ve had bad wheel hop for a while. I broke my differential mount clean in half once, 3 hours from home…

About 3 weeks later my diff bolt broke, it’s was one in the back. Took it to a shop and they had it replaced. Now, about two months later, my diff bolt broke AGAIN. I went and tried to replace my subframe with new diff and subframe bushings (which I was way over my head about, I took half of it apart and put it back together). Said screw it but I did check the diff bolt out. Is there any easy-ish way to remove the nut side of the bolt?

Also why is this such a big problem for me? I do a rolling launch here and there, I’m not doing digs or racing/tracking. Hopefully the poly bushings help out the wheel wobble and stabilize the subframe and diff.
.

your diff bushings are just fucked up but you continued to dog the car, theres no mystery here.

the bolt is bent inside the bushing its not going to want to come out. you need to apply force to it while you turn it.

put diff bushings into the new subframe before you install it or you'll be back here again with the same problems. make sure the threads on the differential arent damaged either.

[atopa2002]

Check with

https://perceptionmotorwerks.com/

[Winter.M3]

Originally Posted by amrazM

your diff bushings are just fucked up but you continued to dog the car, theres no mystery here.

the bolt is bent inside the bushing its not going to want to come out. you need to apply force to it while you turn it.

put diff bushings into the new subframe before you install it or you'll be back here again with the same problems. make sure the threads on the differential arent damaged either.

I for some reason didn't even look at the bushing. I have no clue why it's so bad. I don't track the car, launch it, or do anything crazy. Normal street driving. I had the bolt fixed once and figured the shop would recommend replacing something (they always go over every little problem).

[Winter.M3]

Originally Posted by atopa2002

Check with

https://perceptionmotorwerks.com/

I forgot about this shop, I'll give them a call and compare to The "euro" shop

[Winter.M3]

Originally Posted by pbonsalb

I did not change the subframe but I did DIY the diff and subframe bushings. I was able to lower enough for that work without removing it entirely. You will have to drop it. Disconnect the short brake lines that are enough trouble many don’t replace when doing braided lines, the diff input and axle stubs, and suspension arms and all brake/sensor/diff wiring. Maybe use a 2 stage trans Jack with supporting brackets or a friend or 2 to lower the subframe with diff. Then swap and reinstall. Not easy but not $2-3k if you DIY.

I tried DIY'ing it ha. I'm pretty mechanically inclined but I couldn't for the life of me figure out how to disconnect the parking brake line and couldn't find much info on it except for a bunch of people saying it's easy. I've never touched the ebrake system/lines. I took the exhaust and a bunch of the bolts off, but I don't have a garage or another car to get to work and I didn't want to bug my friend to use his garage for the next few days.

How was taking the bushings out? My friend who works at a Hyundai dealership took my subframe and put in 5/7 bushings but couldn't get the front ones off. NO ONE in the whole shop had a cup that fit on the bushing to press it out. I just bought a kit that should be able to take it out. I know I probably could've found something to DIY it but this will be easy... I've been driving with it broken for weeks.

[Winter.M3]

Originally Posted by Scrippy

Is it the launching or are you hitting your diff on shit? There's some pretty bad scrapes on the bottom of your diff fins. I'm not sure how that happened because I'm pretty low myself out here in the shitty Cali roads and I have zero scratches on my diff. I also have 240,XXX miles. Do you Jack the car up by the diff? I understand there is a valid spot in front of the fins but I still would never do that.

I don't know how it breaks. It was fine one day, I installed a new midpipe, and then while driving it home I felt it banging again. Sure I was doing pulls to hear the exhaust, but I wasn't launching the car, or doing any crazy dumb shifting or whatever. Normal shifting and gas I guess.

I know for a fact I have hit my diff on the floor on backroads, but that was my old diff... which sheared clean in half like I mentioned. This diff casing was bought used, I don't think I caused those scratches. I've only jacked it up from the diff once- to do this DIY.

[Winter.M3]

Originally Posted by North.E92

Are you mt? Wheel hop and any kind of hard shifting/launching will kill your diff bolt solution is to upgrade to stiffer bushings but if your subframe is already bent the bolt might still snap

Yes it's manual. I had TERRIBLE wheel hop when I launched it. This is my first sports car other then a 328... I honestly didn't know it was a real issue until I researched diff/subframe bushings. I didn't do anything that-that bad though. I've owned it for 2ish years and have done less then 10 launches.

I went with 75d (black) bushings from akg. Should solve the problem I hope.

[amrazM]

Originally Posted by Winter.M3

I tried DIY'ing it ha. I'm pretty mechanically inclined but I couldn't for the life of me figure out how to disconnect the parking brake line and couldn't find much info on it except for a bunch of people saying it's easy. I've never touched the ebrake system/lines. I took the exhaust and a bunch of the bolts off, but I don't have a garage or another car to get to work and I didn't want to bug my friend to use his garage for the next few days.

How was taking the bushings out? My friend who works at a Hyundai dealership took my subframe and put in 5/7 bushings but couldn't get the front ones off. NO ONE in the whole shop had a cup that fit on the bushing to press it out. I just bought a kit that should be able to take it out. I know I probably could've found something to DIY it but this will be easy... I've been driving with it broken for weeks.

the parking brake cables just require you to take the rear rotors off then flip the lever where the cable runs into on the botton and remove the cable end from the holder. either that or you can use a allen 5 and remove the parking brake shoes and take the whole assembly apart.


the subframe bushings are easy with the right tool. the diff bushings I used a circular saw blade fully circle shaped and it fit right over the diff bushing housing then a long threaded rod oiled with a combination of washers and nuts. just run it up past hand tight and then pull it out by turning the nut on the backside of the circular saw tool.

[Winter.M3]

Originally Posted by amrazM

the parking brake cables just require you to take the rear rotors off then flip the lever where the cable runs into on the botton and remove the cable end from the holder. either that or you can use a allen 5 and remove the parking brake shoes and take the whole assembly apart.


the subframe bushings are easy with the right tool. the diff bushings I used a circular saw blade fully circle shaped and it fit right over the diff bushing housing then a long threaded rod oiled with a combination of washers and nuts. just run it up past hand tight and then pull it out by turning the nut on the backside of the circular saw tool.

The small lever didn't do anything to the clip for me. I really tried everything I could... but I suck with clips. Maybe I'm just dumb and overlooked how it worked ha.

I got the rear (front) bushings out yesterday. 3 1/8 hole saw fit right over it and pulled it out. The diff bushings and rear (rear) bushings my friend said came right out with a ball joint puller.

[akkando]

Solid subframe bushings and solid or harder than OEM diff bushings (purple) should remove wheel hop.

[pbonsalb]

Originally Posted by Winter.M3

I tried DIY'ing it ha. I'm pretty mechanically inclined but I couldn't for the life of me figure out how to disconnect the parking brake line and couldn't find much info on it except for a bunch of people saying it's easy. I've never touched the ebrake system/lines. I took the exhaust and a bunch of the bolts off, but I don't have a garage or another car to get to work and I didn't want to bug my friend to use his garage for the next few days.

How was taking the bushings out? My friend who works at a Hyundai dealership took my subframe and put in 5/7 bushings but couldn't get the front ones off. NO ONE in the whole shop had a cup that fit on the bushing to press it out. I just bought a kit that should be able to take it out. I know I probably could've found something to DIY it but this will be easy... I've been driving with it broken for weeks.

It is not an easy DIY and beware the short flexible brake lines at the front of the subframe that some might not notice. There is not enough play in them so you must disconnect and access is very limited so it is 1/4 turn at a time with brake fluid dripping on you.

I think some or all of the bushings are pressed in from the top so you cannot pull through from the bottom or maybe it is the other way around. There is a flange around one end of the bushing that will let you pull it in only one direction … unless you break off that flange.

3 pieces of long threaded rod like a 1 meter piece cut in 3 will let you lower the subframe further without dropping it completely. The driveshaft and axles can stay connected to the diff within a limited range of motion but it is enough. There are various wires that must be disconnected.

I did this about 6 years ago so I can’t remember everything. Most shops just drop the diff for better access and that may be the best way.

Parking brakes can be disconnected under the handle as I recall though it can also be done under the rotor if you prefer.

[Winter.M3]

Originally Posted by pbonsalb

Parking brakes can be disconnected under the handle as I recall though it can also be done under the rotor if you prefer.

I tried from the rotor. Every source that I saw said you have to take out the whole center console to reach the ebrake lines. I didn't want to bother. Just got an appointment at the shop! Hope the bushings make it more fun to drive.

[sh0ckc0re]

Did you get the subframe/bushings installed? I want to do the same thing with my subframe this winter as my car feels like it settles into turns twice when I was at VIR this year. I'm sure my rubber bushings are clapped. How does it feel?