360 DIY Gearbox Mount / Bushing Replacement

Hi all,

Thought I'd share my experience here. My tail pipes were drooping dangerously close to the lower edge of the grill indicating that my gearbox bushing had gone bad. A simple examination by eye with a torch revealed that the rubber was torn and snagging so I did my research here on F-Chat and reviewed several threads including........

http://www.ferrarichat.com/forum/showthread.php?t=327663&highlight=transmission+mount
http://www.ferrarichat.com/forum/showthread.php?t=204802&highlight=transmission+mount
http://ferrarichat.com/forum/showthread.php?t=230723&highlight=transmission+mount
http://ferrarichat.com/forum/showthread.php?t=218557&highlight=transmission+mount
http://ferrarichat.com/forum/showthread.php?t=168425&highlight=transmission+mount
http://www.ferrarichat.com/forum/showthread.php?t=268023&highlight=transmission+mount

Thanks to all the contributors in the above and particularly to Enrique / AnExpert with whom I swapped a few PMs for some practical advice.

I considered purchasing the Hill Engineering special tool but from what I'd read i was likely to encounter considerable difficulty removing the old mount even with that tool and given that I hope to only ever do this job the one time I decided I'd seek to find a solution that didn't involve the purchase of an expensive item like that for one-off use.

So I just ordered ordered the part (No. 186698) and when it arrived I set about measuring it carefully to figure out what kind of pulling tool I would need to fabricate in order to achieve the result.

 

I already had my rear under-tray and engine bay side guards removed for some other maintenance I was doing. Both need to be removed for this job.

Next remove the four 10mm nuts that secure the coolant expansion tank and move it out of the way. Note that it's not necessary to disconnect any of the pipes or loose any coolant. Watch out for the washers and nuts!
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Next remove the air box. There are six 10mm nuts - four to the front and one each side towards the rear. Again, look out for all the washers. Un-clip from the MAF and lift out the entire assembly with filters etc still attached.
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Next remove the four 10mm bolts (two on each side) that hold the hard vacuum pipe and the O2 and thermocouple wires to the gearbox support frame. Once the hard vacuum was released I was able to prise it out of the rubber pipe on the right hand side without opening the one-time-use-only standard Ferrari clamp. This gave me enough clearance.
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Now position a jack under the lower gearbox mount point and apply a little pressure to ensure that the weight of the gearbox is supported and proceed to remove the big nut and bolt (22mm) that go through the mount.
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Next, on the right hand side of the gearbox support bracket, remove the clamp that supports the two oil cooler lines.
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Now release all the Allen key bolts (6mm) that secure the support frame. Four at rear, left and right and four more at front left and right. I found the frame was well wedged after removing the fixing bolts so a light tap of a rubber mallet eased it out.
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Once released, the support frame can be carefully maneuvered up and to the side to provide access to the mount. Note that a couple of large washers from either side of the mount will fall out once the frame is moved so be sure to gather them up for use later. I also dropped the gearbox a couple of cm while ensuring that there was no weight on the cross member of the chassis beneath.
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Now the mount is accessible. In my case the centre steel shell came out by fingertip indicating just how perished and worn the unit was......
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Using the blade from a "junior" hacksaw I removed as much of the remaining rubber as possible. This was surprisingly difficult and involved quite a bit of swearing and rummaging around the garage for alternative tools and weapons.

Now this is where some "classiche aficionados" may want to look away!

Having removed the rubber core the next task is to carefully cut through the outer shell (approx 3mm steel). I had to use a hacksaw blade and wasn't able to attach the handle given the limited room to move between the cats. It might have been possible to have made the cuts at the top (12 o'clock) position with a handle attached but I needed to be able to see exactly how deep I was cutting so as to ensure minimal damage to the gearbox casting.

This was hard and slow work. I had to make two cuts. It took the guts of two hours with breaks taken to ease my aching back and cramped fingers. Useful to have a few chilled beers around at this time.
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The first cut didn't provide the necessary relief and I had to make a second one a few mm away from the first. As you get closer and closer to getting through the shell the gap you're working in tends to get tighter and tighter as the shell closes in. It makes cutting very difficult but also means you make such slow progress that it would be rather difficult to cut into the casting to any significant extent.

When I got through the second cut I took a steel chisel and struck the inside of the mount diagonally and it moved pretty easily. Caution here while that casting is undoubtedly very strong I'm sure it's not meant to take any hard / sudden knocks so if there's no give with a light touch it's not appropriate to start belting away at it!

Yes, there's a small amount of over-cut evident. Realistically, this method isn't going to achieve a beautiful flat, controlled cut and you're bound to cause some scoring to the casting. Inevitable.
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The new bushing was 74.8mm diameter. The rubber and centre core stick out either side by 5.5mm so your pulling tool needs to be something hollowed out. In an ideal world you'd get a block of steel or aluminium cut to circle circa 80mm with a 6mm hollowed out inside so that you could pull without putting pressure on the rubber.

Alternatively any flat piece of metal will work but again you're going to want to give that 6mm or relief so that you're pulling on the outer case of the mount only and not putting pressure on the centre.

Additionally, a full circle would be better as this will facilitate pulling even pressure on the mount and cause it to go in straight with greater ease.

I had a scout around the garage to see what I could fashion to make my puller. Here it is pictured on the old bushing. (10mm threaded bar).
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For those of you with a keen eye you'll already have guessed ........ yup, a couple of old brake pads. Cut through the friction material with a hacksaw and then knock out with a steel chisel. 10mm hole through the centre (well, nearly centered) and away you go. Luckily one of the four at my disposal was less well worn than the others and had just enough meat left on it to do the job.
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All my research had told me that pulling in a brand new bushing, with or without the specialised Ferrari or Hill tool was going to be very difficult. I gave the interior of the casting a very light sanding with 400 paper and lubed it up well with some cheap grease.

The new bushing comes with a chamfered edge but only to about 3mm from the leading edge. Using a bench grinder, I took down the leading 10mm of the new bushing from 74.8mm to 74.3mm and the next 10mm from 74.8 to 74.5mm.

Lots of people suggest freezing the bushing and heating up the casting. Many say it makes very little difference but I did both. The freezing process (I gave it about three hours) did bring the diameter down by about 0.3mm so I think it's probably worthwhile. I didn't manage to get an accurate internal measurement on the casting due to the obstructions.

My first attempt did get the new mount slightly crossed up and I think it very important to recognise that early because getting it out again could have been a big problem had I gone too far. Luckily I didn't and was able to reverse and go again pretty easily. This time it went in straight and smooth.
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With the bushing in place (and it's a really tight fit, requiring hard work on the final 15mm of pull) it's a relatively simple procedure to re-assemble everything.

The support bracket took a bit of maneuvering and gentle persuasion with the rubber mallet to get everything to line up nicely. Hand tighten all bolts first and then torque down at 28.5 Nm. Using the jack under the gearbox raise the entire and slide the bolt home with the two washers on the inside between the frame and the mount. Torque to 98 Nm.

Reassemble, stand back admire your work, clean hands and go for a drive.

 

Thanks guys! I couldn't have done it without y'all here!

One thing I forgot to mention in the above......

The new mount has a small arrow on both sides of the rubber. That arrow indicates the upwards facing of the mount. See attached photo again......
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Thanks!

You're exactly right in terms of how replacing items which wear over time can give you back something you weren't really aware you were missing. Last year I had a set of new shocks put into an AMG that I'd owned and thrashed as a DD for the previous seven years and boy oh boy what a difference! You really don't tend to feel the likes of these things going off over time but when you freshen things up, the improvement can be incredible.

In the case of my gearbox bushing, my perception is that pulling away in 1st gear something has changed for the better but I really can't put my finger on just what it is. I just feel that getting the clutch out and the car moving from a dead stop has become a slightly nicer experience.

Pulling away strongly, involving some wheel-spin, has definitely improved. Other than this, nothing else to report.

 

Apologies for late reply. I used the 186698 part. It's common to the 360 / 430 / CS. I understand it's a replacement / improved part to the original but even if not, they're pretty cheap and last up to ten years so I didn't feel the need to consider anything else.