5th Gear Swap
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difficulty: 2/5 for mk4 cars
difficulty: 4/5 for mk3
cars due to firewall clearance and the need for special tools
Introduction
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Since it is very similar for both the mk3, mk4, and early mk5 cars, this article is applicable to all 1995-2006 diesels with a manual 5 speed transmission. This includes the mk3 diesel jetta and passat, and all mk4 diesel jettas, golfs, and new beetles, and the early mk5 jetta. They use different transmissions, but the gearing is very similar and it will work on all these cars. Note that this procedure is not applicable to automatic transmissions, they do not use the same gears or gear ratios as a manual transmission. This modification has not been tried on a 2009 TDI yet but since the manual is 6 speed and parts compatibilty is not confirmed. Also note that the unibody near the frame rails of the mk3 passat blocks the end of the transmission case so there is not very much room to work. You need to find a low-clearance gear puller, simply pulling on it with your hand or trying to pry it out will not remove the gear because it is a machined part that is pressed on. The mk3 jetta and all alh engine mk4 cars have a removable plastic fender liner over the end of the transmission case and have plenty of room. Note that if you have a mk4 pumpe duse (2004-2005), the transmission is slightly different and the cruise control may not work if you change the 5th gear. Mechanically the new gear will work great, but the cruise control gets discombobulated and might not work if you have a mk4 2004-2005 car. It might work fine but there is a risk you will lose the cruise control with those year cars. All other mk4 years and all mk3/early mk5 years should work.
By lowering rpm, you will reduce engine noise and increase fuel economy. After doing the 5th gear swap, you might become alarmed at all the new noises you are hearing due to a quieter cabin! That's how much more relaxed the engine is at normal highway driving speeds. Engine load will increase due to a change in mechanical advantage. Keep in mind that to travel x distance, you need to use y energy at the wheels. The 5th gear reduces the rpm but increases the engine load at the same rpm as before. In other words, to travel the same speed as before, engine load is increased, rpm is lowered, and overall fuel use should decrease from the net effect. You could expect as much as a 4% increase in fuel economy but most people see 2% or none at all since you spend slightly more time in 4th gear depending on your driving style. You will also notice less available acceleration in 5th gear. It should not require downshifting unless you want to pass on a steep hill and are lugging the engine.
Ultimately, I would not recommend doing this swap if you drive mostly in a city or only 10 minutes to work because you will not spend very much time in 5th gear and will not realize any noticeable fuel savings. In fact, if you find yourself in 4th gear more than before your fuel economy may actually get slightly worse. If you plan on selling the car next year I wouldn't recommend it. Otherwise, I would recommend this to everyone else. After driving your car with the new 5th gear, you will realize that this is how VW should have geared their diesel cars. This is almost like losing 5th gear but gaining a 6th double overdrive gear. It's comparable to a double overdrive rather than a traditional 6th gear because many traditional 6 gear manual transmissions' gear ratios put 6th gear near where a regular 5th gear is and are more suitable for low torque engines. This is also a chance to change the manual transmission gear oil, something that should be done regularly anyways.
Lastly, after removing your stock 5th gear, you can sell it to a gasoline VW owner to reduce the final cost. Their cars use the 020, 02J, or 02A transmission, but with shorter gearing and final drive. Your old 5th gear will drop their 5th gear rpm by about 400 rpm! So although the initial cost of the gear kit, gear oil, and shipping is about $350, you can sell your old gears for $100-150!
Gear ratio details
Here is a listing of stock gear ratios. Because you change the 5th gear only, your car's gearing will not change in gears 1 through 4. That would only happen if you changed the final drive. There are a few choices for 5th gear ratios, most people will be happiest with .681 because it lowers rpm enough to be worth the expense and time, and doesn't create an excessive gap between 4th and 5th gears. The loss of torque with a taller .658 5th gear is too great for some people so if you're not sure of which ratio to choose, I suggest getting .681.
MK3
The stock 5th gear ratio in the 02A is .755.
The final drive is 3.157
It uses VW g50 fully synthetic gear oil 75w/90.
Click here for how to
change your manual transmission gear oil: mk3
MK4 non pumpe duse (1999.5-2003)
The stock 5th gear ratio in the 02J is .756.
The final drive is 3.389.
It uses VW g50 fully synthetic gear oil 75w/90.
Click here for how to
change your manual transmission gear oil: mk4
Mk4 pumpe duse (2004-2005, 2006)
The stock 5th gear ratio in the 02J is .744.
The final drive is 4.235.
It uses g 052 726 a2 gear oil.
Mk5 (2005.5-2006)
The stock 5th gear ratio in the OA4 (GQQ) transmission is .769
The final drive is 3.389
New 5th gear ratios: you can purchase either .658, .681, or
.717. Note that .658 requires modification to the spring plate, which is
outside the scope of this article. TDIparts.com includes a pre modified
spring plate in their .658 kit. It also drops rpm by 13% which is too much
for most people. If you have doubts, don't get .658. .681 drops rpm by 11% which is large enough to
be worth the effort. .717 may be a good choice if you never want to add a
chip or larger fuel injector nozzles to increase power but it is also such a
small drop that it may not be worth the expense and time. Note that all TDIparts.com kits also include the
transmission cover gaskets. US dealers will not even order these
parts for you since it is not in their standard ordering system. I had a friend in Germany price the parts in
Euros and after
shipping, it would have cost more than just buying from a US seller, so I recommend
a local seller. Below is an example of gearing changes in an mk4 TDI at
different speeds and rpms.
|
.658 - 13% drop (for the 93-2003 Transporter (eurovan) synchro) .681 - 11% drop .717 - 5% drop
The gasket : 02A 301 215 A
Here is a picture of the .681 gears next to the stock gears. The pictures are about life size. This is the most recommended size. |
 |
Note - the small gear should look similar to your old one but be
smaller. There have been reports of incorrect gears where the number of
teeth are incorrect and there's an additional groove in the gear. Below
left are the correct gears, new vs. old. Below right is an example of an
incorrect gear, note the additional groove in the flat space.
Parts
5th gear kit - it should have 2 gears
transmission end case seal (may be included in the kit)
gear oil - 2.1Liters , see 1000q:
gear oil change mk3 or 1000q: gear
oil change for mk4TDI
super low-profile gear puller (for mk3 cars) OR gear puller (for mk4 cars)
metric tool set
10mm socket
17mm allen wrench
8mm 12 point "triple square" (VW/Audi) bit
14mm 12 point "triple square" (VW/Audi) bit (for mk5 2005.5-2006 jetta
and some mk4)
T60 torx bit (for all mk3 and almost all mk4)
T40 and T45 (or similar tools for removing the plastic fender cover and engine
under cover)
Propane blow torch
PB Blaster
Torque wrench
gear oil catch pan
Procedure
First, make sure that you have all the required tools. I am not kidding here, you will not be able to complete the job unless you have the required tools.
Remove the front driver's side wheel, jack up the car, rest the car on jackstands, and chock the rear wheels as necessary. Make sure the car is in gear and the parking brake are on. Comply with all safety precautions specified in the factory service manual.
Remove the engine under cover and the driver's side plastic fender cover. It is held in place with speed nuts and 1 torx screw. (1996-7 passats have the unibody structure here. If you have a passat, you must determine now if your gear puller will fit in the limited clearance. If not, stop now and attempt the job again when you have the proper tools. If you have a 1996-1999 mk3 jetta or mk4 car there should be plenty of room).
Drain the gear oil with the 17mm allen wrench. As always, make sure you
can open the fill hole first! Refer to these links for more details and
tips.
Click here for how to
change your manual transmission gear oil: mk3
Click here for how to
change your manual transmission gear oil: mk4
Remove the power steering line if it is in the way, and remove the transmission end cover (10mm x 5 bolts, circled in red below). Some gear oil will seep out, so I suggest removing the bolts at the top first. When you remove the bolts at the bottom, have some paper towels and the catch pan ready.
Here is a picture of what an mk4 car will look like. Note the
power steering line in the way and the easy access due to the removable plastic
side panel
Below left is a picture of a mk3 passat as viewed from below. The power steering line is not in the way, but there is very little clearance due to the frame of the car. Your gear puller must be low profile and be able to fit between the red marks. You can also cut the non-structural part of the car, bend it back temporarily, and weld it back, but I would rather use a low profile puller.
Below right is a picture of a mk3 jetta, like the mk4 cars, there should be
plenty of room and no power steering line in the way.
You can now take a look at the 5th gear (outlined in green underneath the
selector gear), the selector
gear (outlined in red), the selector lever (outlined in blue), and the small gear
you need to remove. Warning: check the clearance
of your gear puller! This is the last step where you can still stop the
job. If you proceed, you may pass the point of no return: removing
any one of the major components could require you to remove the rest of the
components to put it all back, or at least make it much easier
Remove the 8mm triple square bolts circled in purple. Then remove the
gear selector pins and gear selector lever. Here is a picture of the parts
removed from the car. Note that the top pin was removed, the bottom pin is
in place with it's 8mm triple square bolt.
Next you have to remove the T60 bolts that hold everything in (circled in purple below). Your bolts may be slightly different sizes. Note that there is a belleville washer, note it's direction and shape - it's not flat! You can even take a permanent marker to mark the sides. You will probably have to have someone step on the brakes and put the car in gear while you remove the bolts. Note how flush the gears are against the shafts.
Note - some late mk4 cars used a M14 triple square bolt instead of a T60
bolt. All mk5 cars use a M14 triple square. A triple square is not a
torx, it's a common VW/Audi specialty tool, don't try to use a torx on it.
The selector gear has 2 circlip springs one in front, one in back. These do not hold the gear in place. I suggest removing the top circlip so you can fit a gear puller arm into the slots.
You must use a gear puller to remove the selector gear (circled in red in above picture) which is pressed in. If you can't fit the gear puller arms in place, you may have to file them down to fit.
Here are some tips to help get the gear off: the gear is pressed on, so don't try to pry it off! Try using PB blaster and squirt it around the center section. Also try removing the washer but leaving the bolt partially threaded in with a gap for something to leave the gear puller bolt to push against. You can also use heat from a blowtorch to heat the selector ring.
If you have an mk3 car, you need a low profile gear puller. I didn't
have one and it was late, so I made one myself. I used a small gear puller
center section, and 2 small gear puller arms. Note that 1 arm tip is wide,
1 arm tip is narrow (You can't really see this in the picture, but this is to
fit into the selector ring slots. The slots alternate 1 wide, 1
narrow). Then I took old allen wrenches, used a blowtorch to soften
them and bent them into s-shapes (followed by a dunking into water to
harden them) to
hold the gear puller arms. Don't bother using soft metal because it won't hold
the force of pulling the gears. Also note that the arms are directly
opposite from each other.
Here is the gear selector with the circlip wire spring installed. Here
you can see how the locks fit into the narrow slots and the wide gaps are empty.
Once the selector gear is removed, the 5th gear just comes off. Note that you MUST remove the large gear and the selector gear BEFORE you remove the small gear. The small gear will not come off before you remove the large gear.
Clean everything. Now clean it again!
Note that the needle bearing just comes out. Can you see from the above picture how the gear just spins freely until it is locked by the selector gear?
Here is a comparison picture of the old and new gears. Note that the
old large gear still has the needle bearing on the inside edge (top left gear)
Here is a picture of the selector ring. Note the grooved tooth (center
of pic) where the
locking teeth sits.
Here is the selector gear. The bronze synchronizer sits between the 5th gear and the selector gear with the teeth pointing away from the trans. The locking teeth are held by the circlips, one above the ring, one below the selector ring.
For reassembly, first clean everything. Then clean it again. Just remember to put the small gear on first, then the large gear w/needle bearing. Then the selector gear. Press them in with a block of wood and a hammer.
If you have time, you can try heating the gears so that they expand slightly.
Note that the washers are not flat washers! You may be able to see wear grooves on the inside or outside edge of the washer. They are belleville lock washer springs and are shaped like a cone to apply pressure against the gear and T60 bolt. If it isn't snug, then it isn't on right. Note that in the below picture, the washer on the large gear is backwards - you can see the wear ring on the outer edge, it should be on the inner edge. Torque the bolt to spec and that should press the gears back on if they weren't 100% on.
Reinstall the selector lever and pins. Clean the gasket and cover surfaces, and reinstall the cover. Refill with gear oil.
Here are the torque specs:
T60 bolts: 59 ft lbs (80 Nm)
8mm triple square selector lever bolts: 18 ft lbs (25 Nm)
Transmission cover bolts: 9 ft lbs
Now go for a test drive and check for any leaks. If everything is okay, go sell your 5th gear to a VW gasser! All of the VW mk3 and mk4 cars that are 5 speed can use this gear. (No 6 speed or automatics)
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