Dropping Transmission on M52 2.8 Manual for shift pin detent servicing

[IndianaRoadster]

Ok, all things are lined up and trans is in position.

I made sure the bolts were cleaned off but there wasnt much on them. I gave them a spray of parts cleaner and a brass brush is around the bolt and they are clean.

Being that I used Kroil (or this likely applies to any penetrate) to help take the bolts out, I want to clean the bolt holes. Do I just give it a quick spray of Parts Cleaner and dry it up with shop paper towel? Or a spray of compressed air? I feel like I should get the oil off that may be in the threads.

I use my Tap and Die set to clean up the threads, then I twist up paper toweling, with parts cleaner and turn it round and round in the hole. If you don't have a Tap and Die set, it's a good investment for a garage.

[Hoyt Clagwell]

I use my Tap and Die set to clean up the threads, then I twist up paper toweling, with parts cleaner and turn it round and round in the hole. If you don't have a Tap and Die set, it's a good investment for a garage.

A less fancy and professional way to clean the holes would be with a twisty brass wire brush* and brake cleaner.Either way, it will be a challenge to get at the top few bolt holes. You may just have to spray brake cleaner in those with a straw.

*Some "brass" brushes are actually brass plated steel and could scratch the aluminum.

[bluptgm3]

File groves or slots in a bolt to use to ‘chase’ the threads.

[kezug]

A less fancy and professional way to clean the holes would be with a twisty brass wire brush* and brake cleaner.Either way, it will be a challenge to get at the top few bolt holes. You may just have to spray brake cleaner in those with a straw.

*Some "brass" brushes are actually brass plated steel and could scratch the aluminum.

File groves or slots in a bolt to use to ‘chase’ the threads.

I have read that, I need to understand why. It will surely make sense once its in use and I see what it does. My guess is that it traps the goop that is collected?


I need help on Torque specs for Transmission Mount to body and Mount to Brace (my mounts are new, OEM and that was replaced last year)
I do have a question back on my transmission mount. I am confused by what I read about what the Torque is for 2 things (the trans support brace to the body and the underside washer/nut to lock in the mount to brace)
I never removed the rubber mount to transmission - left that alone during removal.

My bolt heads for bracket to body and nuts for rubber mount to bracket are taking a 13mm.

Gathered this from various sources of which is confusing to me and/or likely pulling wrong information
Transmission Crossmember to Chassis - 42 Nm or 31 ft-lbs (Odd but no mention of bolt size and also odd, what is crossmember and how does that differ from brace?)
Transmission Support Bracket to Chassis M10 - 42 Nm or 31 ft-lbs
Transmission Support Bracket to Transmission M8 - 21 Nm or 15 ft-lbs
Rubber Mount to Transmission or Bracket Nut - 42 Nm or 31 ft-lbs

So, what are the torque specs? I read its critical to not go to much as it will introduce a lot of vibration. I just want to avoid that.
20250427_003919.jpg 20250427_103456.jpg

[Hoyt Clagwell]

You might want to get yourself the Bentley manual. It's not the best service manual I've ever used but it does have all of the torque specs. Mine is out in the garage. I'll try to look those specs. up for you later tonight if I have time.

Off hand, 31 ft/lbs sounds high for the rubber mounts. I've never installed them myself, just removed them into the trash. The poly mounts I installed called for a torque of about half that. The idea is that you don't want to pre-compress the poly too much or they will act as much harder bushes and perhaps wear/fail faster. I assume it would be similar for the OE mounts.

[IndianaRoadster]

I have read that, I need to understand why. It will surely make sense once its in use and I see what it does. My guess is that it traps the goop that is collected?


I need help on Torque specs for Transmission Mount to body and Mount to Brace (my mounts are new, OEM and that was replaced last year)
I do have a question back on my transmission mount. I am confused by what I read about what the Torque is for 2 things (the trans support brace to the body and the underside washer/nut to lock in the mount to brace)
I never removed the rubber mount to transmission - left that alone during removal.

My bolt heads for bracket to body and nuts for rubber mount to bracket are taking a 13mm.

Gathered this from various sources of which is confusing to me and/or likely pulling wrong information
Transmission Crossmember to Chassis - 42 Nm or 31 ft-lbs (Odd but no mention of bolt size and also odd, what is crossmember and how does that differ from brace?)
Transmission Support Bracket to Chassis M10 - 42 Nm or 31 ft-lbs
Transmission Support Bracket to Transmission M8 - 21 Nm or 15 ft-lbs
Rubber Mount to Transmission or Bracket Nut - 42 Nm or 31 ft-lbs

So, what are the torque specs? I read its critical to not go to much as it will introduce a lot of vibration. I just want to avoid that.
20250427_003919.jpg 20250427_103456.jpg

I'm watching a movie with my wife, so I didn't do much searching, but this might help, it's out of my Bentley manual.
20250427_204804.jpg
20250427_204828.jpg
20250427_204908.jpg

[bluptgm3]

[Hoyt Clagwell]

I'm watching a movie with my wife, so I didn't do much searching, but this might help, it's out of my Bentley manual.
20250427_204804.jpg
20250427_204828.jpg
20250427_204908.jpg

Yes, Mr. Bentley says 31 ft-lb (42 Nm) for both nuts on the mounts.

[kezug]

I'm watching a movie with my wife, so I didn't do much searching, but this might help, it's out of my Bentley manual.
20250427_204804.jpg
20250427_204828.jpg
20250427_204908.jpg

Yes, Mr. Bentley says 31 ft-lb (42 Nm) for both nuts on the mounts.

And yep, I am still confused! LOL But since I am using a 13mm, I must have the M8 sized bolt/nut and it could very well be that I need to go with 16 ft lbs!

I wish I had better recollection of how deep the nuts were on those bolts or how hard they came loosened!

[BimmerBreaker]

I I read its critical to not go to much as it will introduce a lot of vibration. I just want to avoid that.

I have never heard this before in my life

They need to be tight. I've always done those by feel and never had an issue. The master mechanics I know do those by feel too.

[Hoyt Clagwell]

I have never heard this before in my life

They need to be tight. I've always done those by feel and never had an issue. The master mechanics I know do those by feel too.

Are you saying I'm a master mechanic?

Seriously though, I would go by Bimmerbreaker's experience. He has done a lot of these.

In the case of at least some of the poly bushings out there, the manufacturers clearly give torque specs in the range of around 15 ft-lbs. This is partly to do with the design of their bushings and partly because they are firmer than OE and over tightening them will cause them to be over compressed, making them even feel harder than their durometer rating. The ECS 70A poly mounts that I installed came with clear instructions and warned against over torquing them. This is brand specific.

The bottom line is, if you were to experience extra NVH, you can always go in and loosen them up.

[kezug]

I have never heard this before in my life

They need to be tight. I've always done those by feel and never had an issue. The master mechanics I know do those by feel too.

I will see if I can find that again if its meaningful but coming from you, I take it I should forget about it and go tight. With that, then 31 ft-lbs is the mark I will hit for the Bracket to Body and same for nut for rubber mount (under the bracket as I didnt mess with the top nut).

[solimans]

those bolts are m10 if i remember right. but dont trust my memory. get a bolt / nut key. i got one on amazon. that way you can measure the size and thread specs

[kezug]

those bolts are m10 if i remember right. but dont trust my memory. get a bolt / nut key. i got one on amazon. that way you can measure the size and thread specs

Good tip. I realize after seeing such a "key" is that is the M10 or M# for that matter, the size of the bolt or the head on the bolt that a socket fitting entails?

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[kezug]

Good tip. I realize after seeing such a "key" is that is the M10 or M# for that matter, the size of the bolt or the head on the bolt that a socket fitting entails?

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I realize I already knew this...it's the bolt diameter, not the head.

I realized tgough that I was thinking one lead to the other.

I will measure it, but I think it's M8 as they seem small. Perhaps Ms have the M10?

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[kezug]

Ok, I seem to be struggling with how "tight" to put the bottom nut of the bottom part of the transmission mount. I never touched the top not, for removal or to take off the lower or when I attempted to "Tight"en the bottom nut with has the washer.

But I took "tight" as something of a feel that was around 31 ft-lb. The nut kept turning and I never got the "feel" of 31 ft-lbs. I thought I would get to a resistance feel but nope. I could see the rubber mount twist a little as I was "tight"ening the nut but felt it was just going too far. I was taking turns on each side thinking to do that rather than tighten one side.

However, as I backed off the nut, the nut was not coming easily and then I could see the threads on the bottom post of the mount stretched. Not good, will replace.

Ugh! Learning but still. Damn.

Ok, so, I have to know a couple things:
"Tight" in this case (as mentioned a few posts above) is that more towards 31 ft-lbs or about 16 ft-lbs?

If 31, then why did my threads stretch or strip? I can see this, the threads are bad.

I have come so far, done so much and these bolts/nuts are giving me troubles. Doing the OFHG and Water pump/thermostat, no issues at all. LOL

I was able to put the transmission mount to car, easily at 31 ft-lbs I went via torque wrench on that. No issues.

[Hoyt Clagwell]

Ok, so, I have to know a couple things:
"Tight" in this case (as mentioned a few posts above) is that more towards 31 ft-lbs or about 16 ft-lbs?

If 31, then why did my threads stretch or strip? I can see this, the threads are bad.

I have come so far, done so much and these bolts/nuts are giving me troubles. Doing the OFHG and Water pump/thermostat, no issues at all. LOL

I was able to put the transmission mount to car, easily at 31 ft-lbs I went via torque wrench on that. No issues.

My idea of "tight" would be closer to the 31 ft-lbs. That shouldn't strip the threads on a steel bolt of that size. Is it possible that you cross threaded the nut?

[IndianaRoadster]

Ok, I seem to be struggling with how "tight" to put the bottom nut of the bottom part of the transmission mount. I never touched the top not, for removal or to take off the lower or when I attempted to "Tight"en the bottom nut with has the washer.

But I took "tight" as something of a feel that was around 31 ft-lb. The nut kept turning and I never got the "feel" of 31 ft-lbs. I thought I would get to a resistance feel but nope. I could see the rubber mount twist a little as I was "tight"ening the nut but felt it was just going too far. I was taking turns on each side thinking to do that rather than tighten one side.

However, as I backed off the nut, the nut was not coming easily and then I could see the threads on the bottom post of the mount stretched. Not good, will replace.

Ugh! Learning but still. Damn.

Ok, so, I have to know a couple things:
"Tight" in this case (as mentioned a few posts above) is that more towards 31 ft-lbs or about 16 ft-lbs?

If 31, then why did my threads stretch or strip? I can see this, the threads are bad.

I have come so far, done so much and these bolts/nuts are giving me troubles. Doing the OFHG and Water pump/thermostat, no issues at all. LOL

I was able to put the transmission mount to car, easily at 31 ft-lbs I went via torque wrench on that. No issues.

Was there any lubricant on the threads? That distorts things big time.

[kezug]

My idea of "tight" would be closer to the 31 ft-lbs. That shouldn't strip the threads on a steel bolt of that size. Is it possible that you cross threaded the nut?

No as i was able to spin the nut on and off by hand, beforehand.

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[kezug]

Was there any lubricant on the threads? That distorts things big time.

You know, there actually may have been. Unknowingly and from the selector shaft seal leak. I cleaned all that up at the start of all this and before knowing I was taking trans out for the Shift pin detent service. But I never used any cleaner of any kind or wiped anything up on the underside.

They sure look clean though so I am not sure. But I didn't clean them as I didn't use any penetrant to take off the bolts nor saw any mess from the leak.

------

Additionally, I am now worried that going 31 ft-lbs for the 4 outer bracket bolts to car was too much as well. Are the threads to the car easy to distort or would the bolt threads be what goes bad first (in this case, if 16 was the mark but I went to 31)?



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[solimans]

are these the bolts on the rubber mounts you are talking about? if so i know what you are experiencing. this happened to me. they keep turning and turning...

i had to take off the bracket and tighten them down to the bracket first, then put the bracket back in (with the mounts attached), tighten the bracket to the car, then tighten the top bolts on the rubber mounts

i dont know why but it worked that way

[solimans]

sorry typos

[kezug]

are these the bolts on the rubber mounts you are talking about? if so i know what you are experiencing. this happened to me. they keep turning and turning...

i had to take off the bracket and tighten them down to the bracket first, then put the bracket back in (with the mounts attached), tighten the bracket to the car, then tighten the top bolts on the rubber mounts

i dont know why but it worked that way

The nuts that are giving me issues are the ones on the underside of the bracket for the bottom mount post. I either should not have tried to get to 31 ft-lbs (they are M8's) or I may have had some oily residue on the posts (I cleaned up the area well several days ago and before I knew I would be dropping the trans for the Shift Pin/Detent service) although I never saw any residue on the posts and the underside is clean. However, that leak could have put just a enough to cause my problem and it kept that nut turning and turning and digging. I should have known to stop as the post is not that long.

Thank you, I will certainly consider your approach when I install my new mounts.

Now that I think of it, I wonder if the posts being angled had any part of my issue where my wrench was not in line with the angle and I was pulling that nut oddly where it made it dig into the threads? A guess.

I think I am going to go with a slightly less than tight feel. Somewhere between 16 ft lbs and 31 ft lbs. I do have M8 sized nut here.


--- and I just realized a lot of what I was looking for is right here in this DIY in the main FAQ. Perhaps I didnt think to look there as I was not installing the mounts (my mind was not thinking in that terms, but I should have gleaned from an installation/replacement thread of which a lot of my questions are likely in those threads)
https://www.bimmerforums.com/forum/s...sion-Mount-DIY

[BimmerBreaker]

I suppose chalk this up to a learning experience

If it was the studs for the transmission mount you stripped those are part of the transmission mount itself - just buy new ones and try again.

Get them finger tight and then a bit more with a ratchet is usually fine... Obviously the bigger the bolt, the more torque they'll need past the finger tight stage. The trans mount nuts really don't need much

The trans bracket to the body can hold a bit more torque but more isn't better. If you got them tight without them spinning, then leave them alone. You can raise the trans out of the bracket with a jack to replace the trans with the bracket still in place.

[kezug]

I suppose chalk this up to a learning experience

If it was the studs for the transmission mount you stripped those are part of the transmission mount itself - just buy new ones and try again.

Get them finger tight and then a bit more with a ratchet is usually fine... Obviously the bigger the bolt, the more torque they'll need past the finger tight stage. The trans mount nuts really don't need much

The trans bracket to the body can hold a bit more torque but more isn't better. If you got them tight without them spinning, then leave them alone. You can raise the trans out of the bracket with a jack to replace the trans with the bracket still in place.

Thank you.
Yes, I am accepting all this as gaining knowledge and through that learning comes some experience, of which I clearly lack. I am thankful that it was not a more costly mistake! Eek! But all that comes the needed experience I am absorbing as well.

I will end up removing those bracket bolts as I didn't plan that well anyways. Once bracket removed and trans held up by jack, I will install the drive shaft (with bracket removed for more room to deal with flex disc nuts) then put back the bracket and trans mounts with careful "torque" on bolts and nuts!

Then put back the exhaust and bleed the rear brakes!

Will start on this after work today. So close to being done.