Revshift differential bushing too long?

[ewrjontan]

Just installed my subframe/diff/rev shift bushings today. All is well except for the front diff bushing seems to be too long and is protruding about a quarter inch out of the subframe mount. I don't see how the bushing can go anywhere but it does have me slightly concerned. Is everyone else's Revshift bushings like this?

https://imgur.com/aWeRLPd

https://imgur.com/HDcqIIA

[BacDoc]

I have the same problem with either PowerFlex and AKG. The PowerFlex started backing out after a short spirited test drive. I upgraded to the heavier bolt and added some thread locker. So far it seems to be staying but I'd love to figure out why they do this.

https://www.bimmerforums.com/forum/s...8#post29952978

[TostitoBandito]

I haven't attached the diff to mine yet, but will let you know how that goes (today or tomorrow). I have the same bushings.

My inclination is to say that while annoying it shouldn't be a big deal as long as the bolt is still torqued. The bolt they give you is designed for the bushing so it should have enough thread engagement. If it bothers you, there's always the option of pounding out the bushing and grinding down the inside end of it. You should also try and get an explanation from Revshift.

I take it there aren't any gaps around the rear diff bushings which could result in the diff sitting too far forward?

[ewrjontan]

Yeah I don't see the diff going anywhere but I just find it weird. The rear mounts are totally flush with the subframe mounts and the diff is right up against the back of the front mount :/


I am interested in seeing how yours fits. I'll e-mail Revshift but from what it sounds like, their customer service is garbage. Also, did your rear mounts come with washers? I only received one washer for the front mount. I thought it was weird; while bolting the bolts through the rear mounts I figured the bushings could just slide off. I ended up seeing a piece of paper that says to install washers with the bushings. Luckily I had some extras (from my home made balljoint extractor/installer) that were the same size as the as the single washer that they did supply.

[TostitoBandito]

Only the front mount has a giant washer. I don't think the rears are supposed to have them because the side the bolt goes into isn't fully flat like the front bushing is. The only way the bushing could back out is if it manages to slide out while compressed between the sleeve of the diff cover and the inner metal tube in the bushing, which I find very unlikely given how tight my other Revshift bushings have been fitting. Adding washers without lengthening the bolts will also reduce the amount of thread engagement on the rear bolts by at least 1/4 inch or so.

I got the same piece of paper and figured it was just generic for any diff bushings. Some kits might have washers for all bushings, some not. They make them for all sorts of cars after all. And yeah, Revshift is hit or miss in responding to emails. I think I've received one response out of three questions. I also sent Revshift an email about these issues, so hopefully they respond to one of us.

[ewrjontan]

Yeah hopefully someone else can chime in on the rear bushings. The washers slightly compressed/formed into the shape of the bushing recess. I'm curious if maybe I should have used a smaller washer that fits right into the recess. I highly doubt that the bushings would back out without washers but it still worries me :/

[TostitoBandito]

Yeah hopefully someone else can chime in on the rear bushings. The washers slightly compressed/formed into the shape of the bushing recess. I'm curious if maybe I should have used a smaller washer that fits right into the recess. I highly doubt that the bushings would back out without washers but it still worries me :/

A small washer in the recess is pointless since we're in theory trying to prevent the poly from sliding off of the central metal core and all that does is hold the core in. The big washer on the front bushing holds in both the metal core and the poly. And yeah I agree that it's highly unlikely that the poly would back out of the rear mounts given the snug fit, especially if you hammer them in dry. I assume that if Revshift intended big washers to be used with them they would've both provided them and also designed the rear bushings with a longer metal sleeve lined up with the poly on both ends (like the front bushing). I guess you could tap the sleeve to the outside of the rear bushing to line up with your washer, but then it leaves the part of the bushing which touches the diff without a core around the bolt which may overly stress the bolt. This is why I think this was a deliberate design.

[ewrjontan]

Well I mean a smaller fender type washer that I larger than the sleeve and fits in the recess; that way the center part of the bushing is being held in. I'll take it apart over the weekend and see if I can find something.


I just found this pic. Wonder if they changed the design? In the thread where this photo is posted in, the guy says they are revshift bushings.

[TostitoBandito]

Those look exactly like mine, except my stuff is a bit cleaner. What's supposed to be different in the picture? Oh, I guess maybe the metal sleeves seem to be flush, though he could've just hammered them flush to the outside. I'm guessing ours are deliberately slightly recessed so that the bolts get the proper amount of thread engagement into the subframe. If you back out the sleeve like that, you're backing the bolt out of its hole. Or, maybe they changed their design for that reason. Who knows.

I just put my rear bushings in a few minutes ago. I hammered them in dry after cleaning the bores. They're in there pretty firmly, as that last few mm took some force. Also, while I haven't bolted in my diff yet, I did line it up inside the subframe and as far as I can tell I don't have any clearance issues which would cause my front bushing to be pushed out like yours. There should be a little bit of space between the diff and the bushings/subframe, at least if mine is any example.

[hc1001]

I had a similar issue with my AKGs. I couldnt get the front bushing in all the way(2mm gap between bushing edge and subframe ), so when i tightened it all down it actually pressed out the passenger side diff cover bushing about 3-4mm. This kinda changed the angle of the diff, made the input flange point more to the left. It didnt really effect the drivetrain(CV joint) but i went back in and put a washer between the back of the front diff bushing and the diff to fill in that gap and keep the cover bushing from pressing out. I think i had to cut the shape of the washer to fit in that space. In the pics below, I had just started torquing down the front bolt and the rear bushing was coming out. If i torqued it down, the gap would get bigger. I also have a RE diff cover so this might not apply if the stock cover ears are different.

It looks like you used lithium grease on the diff bushings. I would've installed them dry or with soap.

[TostitoBandito]

My diff is in the subframe now. I didn't have any issues with the bushings. Everything fits as it should, and I don't see any way that the rears could back out considering how tight the fit is.

Front
IMG_1408.jpg

Rear
IMG_1410.jpg

[ewrjontan]

Those look exactly like mine, except my stuff is a bit cleaner. What's supposed to be different in the picture? Oh, I guess maybe the metal sleeves seem to be flush, though he could've just hammered them flush to the outside. I'm guessing ours are deliberately slightly recessed so that the bolts get the proper amount of thread engagement into the subframe. If you back out the sleeve like that, you're backing the bolt out of its hole. Or, maybe they changed their design for that reason. Who knows.

I just put my rear bushings in a few minutes ago. I hammered them in dry after cleaning the bores. They're in there pretty firmly, as that last few mm took some force. Also, while I haven't bolted in my diff yet, I did line it up inside the subframe and as far as I can tell I don't have any clearance issues which would cause my front bushing to be pushed out like yours. There should be a little bit of space between the diff and the bushings/subframe, at least if mine is any example.

Kind of hard to tell but it looks like the rear bushings don't have the recess and are flat like the front bushing; but it is kind of hard to tell. Kind of looks like it does have the recess :/

I had a similar issue with my AKGs. I couldnt get the front bushing in all the way(2mm gap between bushing edge and subframe ), so when i tightened it all down it actually pressed out the passenger side diff cover bushing about 3-4mm. This kinda changed the angle of the diff, made the input flange point more to the left. It didnt really effect the drivetrain(CV joint) but i went back in and put a washer between the back of the front diff bushing and the diff to fill in that gap and keep the cover bushing from pressing out. I think i had to cut the shape of the washer to fit in that space. In the pics below, I had just started torquing down the front bolt and the rear bushing was coming out. If i torqued it down, the gap would get bigger. I also have a RE diff cover so this might not apply if the stock cover ears are different.

It looks like you used lithium grease on the diff bushings. I would've installed them dry or with soap.

I saw a lot of recommendations to use copper antiseize so that's what I used

My diff is in the subframe now. I didn't have any issues with the bushings. Everything fits as it should, and I don't see any way that the rears could back out considering how tight the fit is.

Front
IMG_1408.jpg

Rear
IMG_1410.jpg

Hmmm. Well, I guess I bolted up the front first and probably pulled the diff in all of the way which pushed the bushing out. My diff is flush up against the subframe mount. I will go ahead and loosen it up and push it back then

[ewrjontan]

Hmmm, so I ended up inspecting it a little bit. My rear bushing sleeves, which were originally flush with the front of the bushings (towards the front of the car) got pushed back towards the rear of the car. Seems that the rear bushing mounts on the subframe protrude a little bit and caused them to move towards the rear of the car after tightening. I ended up pushing the sleeves all the way towards the rear of the car making them flush with the bushing and giving the front of the bushing more room for the subframe protrusion. Still ended up pushing my front bushing forward the same amount, the only difference is now my rear bushings are flush and work better with my washers. I was able to tap my sleeves in and out pretty easily; granted mine are lubricated.

Super confused though. My only options are to trim the bushing or just leave it as is. I don't see how leaving it will make any difference though seeing as how the diff cannot move forward or back any. Still annoying though. What year is your car? Mine is a '95.

[TostitoBandito]

Mine is a 99, but all this stuff should be basically identical I think.

If I were in your position I'd pop the bushings out, clean the bores and bushings of any grease, and try putting them in dry. If that fails, you can always hit the bores with some spray paint to add a little more resistance/thickness. I know one of the reasons my front diff bushing is going nowhere is because the bore got painted along with my subframe. Not sure the aluminum diff cover should need it though.

When you put in the rear bushings make sure the inner sleeve isn't protruding at all from the front of the bushing. It should be flush or slightly recessed. Otherwise, it will press in towards the rear as you tighten the bolt, and may take the poly with it. It's ok if the inner sleeve is poking out of the rear of the bushing since when you tighten the bolt it will press it in until it's flush with the subframe and that will only snug up the poly. As long as you can get the bolt started, the inner sleeve can be poking out the rear as much as you like.

[ewrjontan]

The sleeve on the rear bushings are flush with the end (rear-end) of the bushings. The front diff bushing gets pushed forward only once I tighten the rear bushings (in other words, pulls the diff forward towards the front of the car).

The only way around this is if I hammer the sleeves of the rear bushings towards the front of the car. This way the diff wont get pulled forward upon tightening. However this makes it more likely for the diff to shift forward and backwards imo; like I said, the lube allows the sleeves and bushings to move a lot easier than I would think.

Seems like the guy in post #2 has a 95 M3 as well. Perhaps there are slight differences?

[BacDoc]

The sleeve on the rear bushings are flush with the end (rear-end) of the bushings. The front diff bushing gets pushed forward only once I tighten the rear bushings (in other words, pulls the diff forward towards the front of the car).

The only way around this is if I hammer the sleeves of the rear bushings towards the front of the car. This way the diff wont get pulled forward upon tightening. However this makes it more likely for the diff to shift forward and backwards imo; like I said, the lube allows the sleeves and bushings to move a lot easier than I would think.

Seems like the guy in post #2 has a 95 M3 as well. Perhaps there are slight differences?

Sounds about right. All my bushings fit except the front diff one. Its as is the diff has come too far forward pushing that bushing out slightly. My upper bushing that mount to the subframe are PF and fit fine but I'm wondering if they are too long and once torqued moved the diff forward like you said.

[ewrjontan]

Yup. I watched my diff move forward and push the front bushing forward/out as I tightened the rears. No negative affects so far with your front bushing being pushed forward I assume? I really don't see the diff moving forward or backward with the way that it currently is. If I pushed the sleeves (on the rears) in and did not use washers I can definitely see it being a problem.

[BacDoc]

Not yet. I upgraded my bolt and added some locktite and extra torque. I put a good 30 mins of spirited driving on it Sunday and it didn't appear to move.