M32 / M20 Gearbox Information / Repairs / Rebuilds / Upgrades
The M32 6 Speed Getrag gearbox is fitted to a wide range of vehicles, including Vauxhall, Fiat, Alfa Romeo and Lotus.
There is a very common problem with the M32 gearbox, the symptoms can vary and some complain of whining but no movement in the gearstick, whilst some complain of movement but no whining!
Generally this is what you should be looking out for:
- When disengaging the clutch in 1st gear when pulling away, whilst holding the gear stick, it will move back into your hand, sometimes by 10-20mm! (the greater the movement, the worse the problem)
- When applying the accelerator in 5th or 6th gear, the gearstick ‘twitches’ in comparison to 3rd and 4th (although in rare cases there can also be twitching in these gears due to different bearing issue)
- Whining sound coming from behind glove box area
- Specifically on Corsa, Punto and Mito models; when turning right at 30mph+ you get what is best described as like a disc rubbing noise
- Movement / whine more noticeable in 1st, 2nd, 5th and 6th gears
The gearbox problem which results in all of the above symptoms is a result of one bearing – specifically the bearing on top of 6th gear. The bearing rollers wear, which causes the movement in the gearstick, which is causing the internal gear shafts to ‘float’, and the whining is caused by pits in the bearings, which can be seen in the image below. (Click to enlarge)
It is also quite common to get a constant whine in all gears from 20-30mph onwards, regardless of whether the clutch is engaged or disengaged, and which intensifies with speed. Often misdiagnosed as differential bearings, this is caused by pitted pinion bearings which can be seen on inner and outer races below.
The 2010-2012 gearboxes have seen more issues with pitted pinion bearings than earlier versions – this is due to GM changing the bearings to FAG and NGBC, as opposed to the earlier Timken bearings.
Bearing failure can be caused by a combination of things, mainly linked to poor gearbox design, excessive oil temperatures along with failure to change the gearbox oil (not part of the service schedule).
- It is commonly thought that high torque output causes the bearings to fail on remapped cars etc. – but this simply is not the case. We have cars running 350-400lbft without issues, yet we can see low output engines (1.3 CDTI / 1.8 non-turbo etc) experience issues. It is true that the greater the power, the more heat will be generated, but a high percentage of the cars we repair are run-of-the-mill cars, which still run into gearbox issues. Essentially, doing long distances on the motorways, during which 95% of the time is spent in 6th Gear. Transfering the engines torque all the way down the input shaft, across to the 6th Gear (closest to the end on the output shaft), and then back down to the final drive put maximum load on this small top bearing.
- The bearing which commonly fails and causes issues sits on top of one of the two output shafts on this 6-gear gearbox. Gears 1, 2, 5 and 6 are all on this shaft – hence why the issues typically manifest in these gears. Reverse and 3rd and 4th gear are situated on the other output shaft. In extremely rare cases we have seen issues with these gears instead, but this is only the case for >1% of repairs we have carried out.
- When driving with the gearbox issue, we advise to use avoid using 5th and 6th and stick to 3rd and 4th gears mainly, as this will transfer the engines torque across the other output shaft, taking load off of the failing bearing.
- It is also worth bearing in mind that failure can occur over time as well as mileage- if your car has failed with relatively low mileage, it could be down to the age of the bearings rather than the number of miles covered. It is equally possible that a high-mileage new car and low-mileage old car would fail.
- If left unattended, the outer bearing race can start to spin, which causes the wear on the casing eventually popping out of 6th gear (stripping the gear) which can then finally punch a hole in the casing. Once this happens, it is highly unlikely that we will be able to repair your gearbox, due to the internal damage caused, making the repair uneconomical. Our advice is therefore to always catch the issue early, and book in for a repair as soon as possible in order to avoid further damage and associated costs.
Gear selection issues
Completely separate issue to the bearings mentioned above, and typically more common on the VXR / more powerful models due to the nature they are driven.
With selection issues most common on 2nd, 3rd and 4th issues to look out for are
- Popping out of gear, once selected and power is applied the gear stick returns to neutral
- Crunching when attempting to select gears, usually worse at high rpm
- Poor gear change / Selection
The cause is typically down to wear and tear, mainly caused with more enthusiastic gear changes. The engagement teeth on the problem gear / hub wear down and lose their points becoming bured / rounded as seen below, if left eventually popping out will occur.
Occasionally these issues can also damage the nylon fork guides, which then require replacement
Generation 1 – 2004-2013. Then Gen 1 Gearbox is the most common gearbox we see for repairs, with the main issue being related to 6th gear bearing, Few versions were made with bearing make change and guides added in 2010, however these did not resolve the problems. Installed with 55mm Top bearings.
Generation 2 – were released from MY12.5-MY2017 (2012 – 6 months in), although some cars were not installed with these until 2013+. These 2nd generation gearboxes come complete with improved oil galleries and, more importantly larger bearings (55mm vs 62mm OD) with dramatically bearing surface area. But…..we still see these gearboxes in for repairs with the ‘All gear whine’ from pitted pinion bearings. The larger bearings help dramatically with the common 6th gear bearing issue – to date we have not seen a bearing issue bar a few light wear marks when in for pinion bearing repairs.
Generation 3 – MY17-Present With the 3rd Generation in the latest vehicles, with 3rd end casing consisting of different bearings again, however little information or parts are avaible currently.
Below is image of a Generation 2 casing (Top) and Generation 1 Gearbox (Bottom), easiest way to identify is the large gallery vein which can be seen running from the Center to top left, and lack of oil filler / level bung on the lower left hand side, where then Gen1 has this located.
Repair / Rebuilds
Being such a common issue across the range of models / engines, since 2011 when we carried out our first repair! We have completed over 2000 of these gearboxes repairs / upgrades. Using all Genuine tools which we have invested heavily in, therefor helping us perform upgrades to GM specs, allowing us to perform a quick and efficient service. While also offering one of the best warranties on work carried out – 18months / 18,000 Miles subject to terms and conditions.
Using only the best components, bearing manufactured by Timken/SNR who are the leading bearing manufacturers to the automotive industry. While also using a high gear grade gearbox oil – Fuchs Titan Sintofluid 75w80.
Our normal repair service is offered as – Drive in drive out, while you wait same day repair, which takes under 4 hours to complete.
Normal bearing replacement service:
Includes replacing all 6 gearset bearings, which consist of: the faulty ‘6th gear’ bearing; 4th gear output shaft bearing; both input shaft, and both pinion bearings. This involves removing the complete gear set from the car, removing both input and output shafts/gears sets, and replacing all inner and outer races.
Casings are cleaned thoroughly and a full inspection carried out, and refilled with high quality oil once rebuild is complete. However we do not remove the complete gearbox from the vehicle, so clutch inspection / change is not offered with this service.
- £599 – Drive in drive out, while you wait service (Applicable for all vehicles listed, except Lotus)
- £450 – Gearbox supplied only, (Or use after our gearbox remove service, if clutch change required)
All Prices include VAT, parts (as mentioned) and labour
Generation 2 Retrofit service – includes installing a new genuine GenII GM casing with larger bearings, installing with our Bosch M32 special tools to ensure professional fitment of the retro installation. This service requires full gearbox removal, as this is the only way to correctly set up the new casing in our eyes. Therefore a while you service is not offered, how ever same day service is still possible. Prices do not include gearbox removal.
- £380 – Top casing only’ service, leaving the current bottom bearings, and installing only the ‘3’ larger bearing for the retrofit, idea for customers who have had recent overhaul, otherwise full bearing replace advised.
- £660 – Full gearbox overhaul- stripping gears shafts completely down, cleaning and installing with all new gearset bearings and drive shaft seals along with the retrofit.
Please note these prices are subject to gearbox removal costs– there is no extra labour costs to install a clutch kit if supplied by WGM, LSD installs occur minimal costs at the same time.
Gearbox Removal costs
For customers who are looking for clutch replacement or clutch upgrades, full gearbox removal is required and subject to our remove / install charges below.
Corsa D – £240
Astra H – £300
Astra J – £300
Zafira B – £300
If your vehicle is not listed please get it touch for a quote.
If you was looking for the Gen2 upgrade on a Astra H VXR – £300 gearbox remove / install charge + £660 Retrofit service = £960 Total
Corsa D wanting a normal gearbox repair the total would be £599. However if you required on of our clutch upgrades at the same time
£240 gearbox remove / install charge + £450 normal gearbox repair service = £690 Total
All Prices include VAT, parts (as mentioned) and labour
Gear Selection issues
Gear selections are completely different issues to the bearing issues, and are not related in any way.
If these repairs are carried out at the same time as any of the above repairs, no extra labour costs will be charged.
- £399/ additional £120 at the time of gearbox repair – For 3rd and 4th gear selection issues. This consists of new genuine 3rd gear, 4th gears, and hub. Sometimes it may also be required for us to replace the selector fork (£50).
- £380/ additional £100 at the time of gearbox repair – For 2nd Gear selection issues we replace the 2nd gear and hub, again with genuine parts
Repairs are drive in, drive out while you wait, including labour to strip the gearbox and replace mentioned parts, rebuild and refill with high quality oil.
All Prices include VAT, parts (as mentioned) and labour,
One popular upgrade we offer at the same time as our repair service is the 4H-Tech short shifters, with minimal labour charges if installed at the same time – 4H Tech Short shifts
We also have a range of Limited Slip Differentials (LSD’s) – LSD Options to maximize traction and dramatically improve handling , with minimal labour costs to install while the gearbox is removed
Those looking to replace slipping clutches, or simply upgrade with more power in mind we have several options from OE replacement, or uprated friction plates / paddle clutches along with solid mass flywheel conversions. Please get it touch with you model / engine or search under Transmission upgrades on WG Motorworks Shop , No extra labour is charged if gearbox is already removed.
6th gear ratio change – £90-£120 (+£80 If ECU cruise control programming required) Please enquire
Gearset ratio change – (please enquire)
Gearbox oil breather – (please enquire)
For bookings, email – firstname.lastname@example.org
The 6-Speed M32 / M20 Gearbox is fitted in the following models (some may not be listed)
Astra H 2.0 Turbo VXR
Astra H 2.0 Turbo
Astra H 1.6 Turbo
Astra H 1.9 CDTI
Astra H 1.3 CDTI
Astra H 1.7 CDTI
Astra J 1.4 Turbo
Astra J 1.6 Turbo
Astra J 1.7 CDTI
Corsa D 1.6 Turbo
Corsa D 1.6 Turbo
Corsa D 1.3
Corsa D 1.7 CDTI
Corsa E 1.4 Turbo
Corsa E 1.6 Turbo VXR
Insignia 1.4 Turbo
Insignia 1.6 Turbo Z16LET
Meriva A 1.6 Turbo VXR
Meriva B 1.4 Turbo
Mokka 1.4 Turbo
Mokka 1.7 CDTi
Vectra C / Signum
Vectra C / Signum 1.9 CDTI
Zafira B 2.0 Turbo Z20LEH
Zafira B 2.2
Zafira B 1.9 CDTI
Zafira B 1.7 CDTI
Zafira C Tourer 1.4 Turbo
Punto 1.4 Turbo
Punto 1.9 CDTI
MITO 1.6 CDTI 1.9 CDTI
Bravo 1.4 Turbo
Mito 1.4 Turbo
Mito 1.6 CDTI