M47 Noise Issue - Solved
 

Hello all,

On April 2020 I open this post about my M47 gearbox noises:
https://www.volvoforums.org.uk/showthread.php?t=306354

As this car is only my hobby car, I don't drive it so often, so it made only ~1500KM in that year.
Two months ago I've decided that it is time to remove the gearbox from the car and started to disassemble it in order to find the source of noise. It was noisy at gears 1,2,3 and little bit on 5. No noise on 4th.
In addition, once in neutral and clutch is engaged (pedal not pressed), there was noise. When clutch pedal was pressed, the noise stopped.
The gearbox P/N is 1023561. It's an M47 with mechanical 5th gear on the back and a cable speedo.

TL;DR - The noise came from the input shaft bearing - That's SKF 6306NR.

I started by ordering a gasket and seals kit - This is P/N 271575. For the other parts I had to wait until gearbox was removed from vehicle.

In order to remove the gearbox, it is necessary to remove the following:
1. Clutch cable
2. Reverse light wiring harness
3. Driveshaft - 4 screws on each side, plus additional 4 for the mounting
4. Gear lever - remove the rubber boot, allen screw from the bottom and holding pin, then remove lever from the inside of the car
5. Gearbox rear mounting - these are 4 bolts and one nut that is holding the rubber mount to the metal bar mounting. At this point, the gearbox rear part should be supported using a hydraulic jack or something similar.
6. Starter motor - disconnect battery, mark the wires connection to the starter actuator, remove two bolts.

The starter motor bolts are part of the gear housing mounting bolts, so in addition to those there are 6 more around surrounding the housing.
After removing these bolts, the gearbox is ready to slide back and down in order to remove it from the vehicle.
In some videos I've seen on the web, it looks like the box can be removed together with the shift lever (item No. 4), but I couldn't do it at home. The Haynes manual also recommends removing the lever.

This is how it looks like when outside of car:
Attachment 136524

I started by removing the front gearbox housing and clutch fork (inside the housing), which revealed the input shaft bearing and counter shaft front bearing.
Attachment 136525
Replacement for those are:
1. Input shaft bearing - SKF 6306NR
2. Counter Shaft front bearing - SKF NU304ECP - Needs to be machined with a small groove for ring.
3. Clutch release bearing - SKF VKC 2065
4. Small oil seal in the housing itself which is part of the gasket kit.

Then, I removed the upper cover to see the condition of the gears, forks and synchro-gears.
At first, the gears coulisse mechanism needs to be removed. Notice three washers below and the spring+metal ball (below the spring).
Attachment 136526
After mechanism removed, it is possible to see gears and forks of gears 1-4 and Reverse. As I didn't have any problems with those, and also didn't have spare parts, I left those intact.
I removed two locking pins of the selector rods, then I could slide out the main rod, the second one needs to be removed from the 5th gear separate mechanism.
Attachment 136527

I continue with the disassemble by removing the output flange and lever mount. Then removed 6 bolts (including two that holds the rubber mount), which revealed the output shaft bearing and counter shaft output rear bearing.
Attachment 136528
Replacement for those are:
1. Output shaft rear bearing - Volvo P/N 1232899+1232993. Not possible to find it anymore. I thought that SKF NU1007ECP can replace it, but it comes in one part (outer race and bearing) so it couldn't be installed.
The bearing was still in good condition so it was re-installed.
2. Counter shaft lower bearing - SKF L68149/Q

Then I removed the rear box, which revealed the 5th gear mechanism with its bronze fork. I removed also the speedo gear during this.
Attachment 136529.
After removing the fork locking pin I was able to remove its operation rod.
removing the six bolts from the cover has revealed the middle part bearings (between the main box and the rear box).
Attachment 136530
Replacement for those are:
1. Main shaft middle bearing - SKF 6306NR
2. Counter shaft middle bearing - SKF L68149 +L68111

In addition, there are three needle bearings that you will meet during the work. I didn't have part numbers for those as I just went to the bearing shop and ask for the same size. I could locate only one of the three.
Eventually, it looked like this:
Attachment 136531

And of course - the noise source:teeth_smile:
Attachment 136532

Then, cleaning all parts, installing gaskets with and seals, and re-installing everything.

As I do all the work at home, it took me about three days from removing to re-installation of the gearbox.
After 250KM everything seems to be working good. No noises, no leakages.
I plan to replace the oil again at 1000KM.

Good article.

You're a brave man opening a gearbox up but good on you for doing it! I hope your repair lasts you for a very long time.

Mine turned out to be the final drive bearing. It vibrated so much, at certain speeds, in the end that it was shearing the down pipe flange.

As that end is so well supported it took some time to find. When the box was removed and the bearing removed I could not believe how much that bearing moved at 550,000 miles. It did well!!

I was not as brave as you, I got Salisbury Gear Boxes to do it.

BrianH

550,000 miles is very seriously impressive!