I ve been reading some on this mystery VW 6 speed and is a 02A/02J's cousin. I found one about 400 miles away from me and decided to get it! The bellhousing is a 4 cyl. bolt pattern so it must be change out. For parts I have my buddy's 02A with a peloquins diff in it, he stripped 3rd pretty good. The 02S is quite cool, it really is just like an 02A, but there are several interesting changes. There are plastic oil "guiding" pieces in it, guiding more fluid to the diff. The synchronizer design is changed, and just playing with them you can definitely tell that they grab stronger to the gear then the previous style.
After doing all the clearance tests with new bearings installed, found that the mainshaft clearance is such that no Vw shim will make it right, so had to machine the bearing race itself to achieve the proper 0.20mm preload. The differential swapped right in, meaning 02J and 02A diffs are identical, aside from bolt in/ pop in axle flanges. You do need the 02j-B diff if you gonna buy one specifically for the 6-speed, the o2S has the new style ring gear, 113mm ID, and the 12.25mm bolt holes. I am not buying a new diff because of financial reasons, and instead having my diff machined to accept the new style ring gear and bolts. The factory 02S diff will work for the swap, you'll just have to get some 100mm axle flanges, and install the speedo drive gear on the 02S diff (and it has a spot for it!). This new transmission also uses quite heavy diff preload springs, much tighter then any previous VW trans I've played with. So if you just want good fuel economy, you will still enjoy the gearbox as is.
I am writing on my iPhone, but within next few days I will update everyone with pictures and all the little things I found out about this unicorn transmission. I ve been working on this project for several weeks now and have gathered quite a bit of information, including gear ratios and such. Check in now and again for all the updates.
*Bearings and Seals: Get them for the 02A, same part numbers for bearings, and seals to match the axle flanges you are going to use.
*Ring and pinion is Identical to the CDM, it is a 3.647 final with identical number of teeth to the CDM. The gears themselves are shorter ratio though, giving better acceleration, and a top speed of 181mph with 205/45/16. At 80 MPH on that same tire I should be a hair over 3k rpm, which will build much less heat at cruising speed, and should use much less gas. If I cruise at 85mph-25mpg, at 75mph-28.4mpg, of course the drag at the higher speeds needs to be accounted for as well. From what I gathered these transmissions come with either 3.94 final, or a 3.64.
This is the 5th and 6th, it does use an extra set of needle bearings in the cover for support reasons. Which is great as the two shafts have even more support from separating under load:
The gears and diff in the 02S/0A4 housing:
The two halfs assembled to measure clearances to shim for proper preload:
And made it look pretty haha:
In this last picture you can see the lip where the axle flange goes into, the 02A does not have that. This lip is what holds a new style seal, which is larger in OD and ID. Below it the case is machined for a regular 02A seal, which I've already test fitted with no issues. My only concern is flange clearance, in which case that lip will have to be machined off completely. The reason I am staying with the 02S/0A4 main case is because the bearing are already in it, so less money spent and less work required. You could use the whole 02A and swap all the gears in (I havent inspected that for sure though, so dont take my word for it as of yet).
She is finally finished! Ran into some complications with making the ring gear work on the 02A diff, but its done, ended up TIG welding small stitches in between bolts in 4 sections opposing each other for balancing. Picking on which rod to use was a bit of a challenge as couldn't find out exactly which metal is used for the ring gear. Silicon Bronze rod ended up being the one that I went with after discussing the application with several people. And because VW trans sealer is $80 a tube (LOL), I just used some quality Hylomar to seal the trans. Gonna install it this weekend.
Another complication is the way the shift cables are adjusted, as the MK5 and up VWs use a threaded rod on the cables, vs. a slip and slide on the Rrado, but I may weld the 02A selector ends to the the 02S, that way I'll be able to alter the mechanical advantage of the levers as well, creating a shorter throw. I have till the end of the week to come up with a conclusive decision .
More to follow.