02S 6 speed conversion into 02J case

[Matt-98AHU]

Poking around some used cars a couple months ago, I came across a 2020 Golf 1.4 TSI with a 6 speed. This was news to me as the earlier 1.4s came with a 5 speed as their optional manual transmission.

I've been looking at transmissions in the VW Parts catalog via Partslink24.com lately just to see what's available in our market. An earlier observation was made that 1.8TSI 5 speeds use some very nice gearing that would be great for a TDI as well. Same 3.39 final drive, but taller 3rd, 4th and 5th gears.

In a mk4 TDI gearbox, generally you're going to see the following:

1.36 3rd gear
0.97 4th gear
0.75 5th gear

The 1.8TSI 5 speed box has:

1.27 or so 3rd
0.87 4th
0.66 5th

That gear spacing would at least help address the big complaint about installing a taller 5th gear, but having that large drop from 4th to 5th. If you've driven up steep grades and had to slow down for slower traffic, you might appreciate more how a 0.658 5th can be too tall while the 0.97 4th is almost uncomfortably short in real specific situations like that.

So, imagine my delight and surprise when I plugin the VIN of a 6 speed manual 1.4 TSI and see what transmission code it has, then look in the parts catalog to find out that this transmission is NOT a 02Q/MQ350 with the twin pinion shafts, but it is an MQ250 02S, which is effectively a 0A4 5 speed with another gear added to it.

The 0A4 is just an evolution of the 02J, which is itself is a mild evolution of the older 02A that dates back to the late 80s with the first Corrados. 02A/02J/0A4 "MQ250" gearboxes are about as close to Lego interchangeability as it gets for their internal parts for a design that dates back close to 35 years at this point.

After looking up the 6 speed, I was pleasantly surprised at how great the gearing looks for a Mk4.

Same 3.39 final drive a Mk4 TDI uses, but has very close to identical 1st through 4th gears. 1st is actually shorter still than the stock 1st, but it won't be super noticeable.

5th gear is a smidge shorter at 0.77 va the stock 0.75, and 6th is 0.625.

I like this because it means good used parts will be a lot more readily available in North American bone yards as opposed to the 02M 6 speeds that we did not get here for TDIs in the states natively.

This is also interesting because it means you keep the same shift bracket, same axles, starter and the much more affordable clutch and flywheels that the 5 speeds use. You also aren't going to have selector failures like the MQ350/02M/02Qs are known for, not to mention the clutch hydraulics, especially the slave cylinder, are more reliable and do not require transmission removal to replace.

The only drawback aside from the amount of work to swap cases is the fact this is a "weaker" gearbox than the MQ350s. But, there also are plenty of people making a good amount of power in the 5 speeds with no real issue. So, for my purposes, this is an attractive solution.

The challenges of performing this swap: this has 0A4 casing halves, meaning no provision for a vehicle speed sensor, there is no flywheel TDC hole with pointer, which is important for ALH timing belt jobs, and two of the three shift linkage bracket bolt holes are in the wrong location.

This is why swapping into a 02J case is necessary, especially for the VSS.

The last 'gotcha' is VW changed the pinion bearing whose outer race presses into the bellhousing. One other person had already attempted this swap upon my recommendation and found that the pinion shaft itself is 1 mm larger diameter than the older 5 speeds where that bearing presses onto the end of the shaft. The bellhousing machining was also changed drastically to accept this very different outer bearing race, and itbalso uses different set of shims for setting bearing preload.

So, I will have to lathe 1 mm diameter off the short end of the pinion shaft to get the Mk4 bearing to fit so I can put all these guts into a 02J case.

EDIT: to add to the above, I also lathed 2 mm length off the end of the pinion shaft on top of the 1 mm diameter to prevent interference issues with the case where the bearing race presses into the bellhousing.

That all being said, I have obtained a couple used 02S 1.4TSI gearboxes and will be starting on it this week. Chances are good I'll be able to finish a gearbox this week, but won't be able to install it in my car for a couple more weeks.

I think I may do a video series on this. I started with one today outlining the basic premise of what I'm going to do. You can find that here:

PART 2: Teardown

PART 3: Pinion shaft disassembly

PART 4: Differential disassembly, VSS gear trial on original diff

PART 5: Installing ring gear onto Wavetrac diff, speedo gear, bearings, comparing diff bearing styles 02S/0A4 vs 02A/J

PART 6: Installing bearings and races

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youtu.be

PART 7: Diff and input bearing free play checking, shimming and friction torque checking.

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Part 8: Pinion shaft bearing preload and gear stack:

02S 6 speed to 02J--Pinion preload and gear stack

This video, I check the pinion bearing free play, install a shim, friction torque double check, and then ended up having to go one size up on shim to get the...

youtu.be

PART 9: Final assembly! No wait, no it's not... Mismatch between 02J case and 02S/0A4 selector fork assembly.

02S 6 speed to 02J swap--The Home Stretch (Or is it??)

Murphy strikes back just when I thought I was on the home stretch. 02J case doesn't want to work with the 02S/0A4 selector fork assembly.

youtu.be

Part 10: No, seriously. Final assembly.

02S 6 speed into 02J--Final assembly!

After switching back to the 0A4/02S back case, resetting bearing clearances once more, it's time to do final assembly. At the very end there are two photos o...

youtu.be

Test drive!

02S 6 speed into Mk4 02J--Test Drive!

All back together, car has a few other unrelated upgrades I did at the same time. Super happy with how it turned out. Absolutely love the gear spacing, and l...

youtu.be

 

[Matt-98AHU]

I should also add that either the 1.8TSI 5 speed (usually QSY or NZA codes) or this 1.4TSI 6 speed will be drop-in upgrades for MK5 BRM owners.

The 1.4TSI 6 speed codes I primarily look at for now are TDZ and TKR code gearboxes. There are a couple newer versions that start with 'U' For the code, but I don't recall exactly what they are off the top of my head, and at this point, they're so new (think 2021 or newer) that there's very few floating around used yet, and the few that are run a lot more money than the earlier TDZ and TKR codes. They're effectively the same. So much the same that I'm not real sure why VW bothered to give them different codes!

 

[Windex]

As someone who modified my 02A to a 6spd with a eurotuning kit, I am interested in the outcome.

 

[Matt-98AHU]

As someone who modified my 02A to a 6spd with a eurotuning kit, I am interested in the outcome.

Yeah, I did John Jackson's a little over 10 years ago in his B4V (may he rest in peace). I believe Whitbread owns the car now. Nice thing with those was they could be done without splitting the case. This also meant they'd work for those 02As.

These 1.4 guts will work for a Mk4 or Mk5 TDI, but the final drive in all of them is shorter than the Mk3/B4 TDI. 3.16 in those early cars and 3.39 in later ones, all due to how much smaller of a diameter tire they use in the early cars.

But, this is all OE parts that will continue to be available for a long time. Definitely is a lot more work, though! I had John Jackson's Eurotuning kit done in a couple hours. This thing will probably take closer to 7-8 all told!

As these get older, the transmissions will become cheaper to buy used, of course. These I managed to get for about $800/ea including the $75 core charge.

 

[oilhammer]

Neat project, Matt. I had thought about using one of the 5sp units from the NCS 2.slo cars, as those too are geared taller.

My issue is that the later VAG gearboxes seem to have some widespread weak bearings in them, I've seen a lot of them have awful gear whine and even wiped out carrier bearings at relatively low mileage. I suspect cheap (Chinese) sourced bearings could be to blame, but who knows. Curious what you find inside when you tear one apart, if you can see anything.

I've resisted the taller 5th in my Golf because of the reason you stated above... that awful gap from 4th. If I never towed anything, I could live with it. But there are times on the highway that I do need to drop into 4th as it is.

 

[bigsexyTDI]

Definitely following this... coolest thing that has happened here in ages!

 

[pudman2003]

Great video Matt, I'm so excited!

 

[Matt-98AHU]

Neat project, Matt. I had thought about using one of the 5sp units from the NCS 2.slo cars, as those too are geared taller.

My issue is that the later VAG gearboxes seem to have some widespread weak bearings in them, I've seen a lot of them have awful gear whine and even wiped out carrier bearings at relatively low mileage. I suspect cheap (Chinese) sourced bearings could be to blame, but who knows. Curious what you find inside when you tear one apart, if you can see anything.

I've resisted the taller 5th in my Golf because of the reason you stated above... that awful gap from 4th. If I never towed anything, I could live with it. But there are times on the highway that I do need to drop into 4th as it is.

I've noticed they have changed diff bearing part numbers. The other weird thing is the repair manual has actually DECREASED diff bearing pre-load compared to earlier cars. They only call for 0.25 mm preload vs 0.40 from the earlier cars.

I will be using the older bearing part numbers and also using the higher preload.

The other weird thing with 0A4 5 speeds and these 02S gearboxes that use 0A4 housings is the casting for the bellhousing effectively completely blocks natural drainage into the diff. Hence the need for VW's very weird drain and fill procedure that requires you to remove one of the shift pins to get ALL the fluid out. And of course the poor drainage also means you have to fill it with a specific amount from a point higher than the traditional check/fill plug.

There have been a LOT of these gearboxes that went chronically underfilled because not enough techs realized that VW made such a stupid design change.

 

[ts888]

Sooo, I should wait a week to drop off my 02J case?

This is cool stuff. Add a Peloquin and it would be perfect -- winter traction too!

 

[Matt-98AHU]

Sooo, I should wait a week to drop off my 02J case?

This is cool stuff. Add a Peloquin and it would be perfect -- winter traction too!

I'll be adding a Wavetrac to mine!

There is more progress today, working on editing a couple videos...

Case is open at least and pinion shaft is stripped. Definitely learning a couple lessons the hard way. A wrench might have gone flying and a bearing exploded in my face.

You know, just another day working on stuff.

 

[hskrdu]

Following!

 

[jeffecor]

Hmmm very interesting differently going to follow.

The VSS can be switched to pickup from the ABS on the mk4 cluster gauge that's done in the eeprom that wouldn't be a issue for me. So beside the issue's of this
(The challenges of performing this swap: this has 0A4 casing halves, meaning no provision for a vehicle speed sensor, there is no flywheel TDC hole with pointer, which is important for ALH timing belt jobs, and two of the three shift linkage bracket bolt holes are in the wrong location.) would the 02S work with some modified would it bolt in and use the 02J flywheel, axles and starter?

 

[Matt-98AHU]

Hmmm very interesting differently going to follow.

The VSS can be switched to pickup from the ABS on the mk4 cluster gauge that's done in the eeprom that wouldn't be a issue for me. So beside the issue's of this
(The challenges of performing this swap: this has 0A4 casing halves, meaning no provision for a vehicle speed sensor, there is no flywheel TDC hole with pointer, which is important for ALH timing belt jobs, and two of the three shift linkage bracket bolt holes are in the wrong location.) would the 02S work with some modified would it bolt in and use the 02J flywheel, axles and starter?

The only thing that's also really off about these is the bellhousing does space the transmission a little further away from the engine. If I were to get a good shot of where the casting for the axle flange seal on the passenger side is vs. the bellhousing where it meets the engine, you can see on the 02J it's completely flat. The 02S (and 0A4) space the gearbox a little further back. mk5 and up cars are technically supposed to have a different flywheel that has additional offset to correct for this.

This spacing also means if your current drivetrain alignment has the transmission mount bolts in the slotted holes in the transmission mount are already more towards the driver side, the 02S would push it even further still to the driver side.

And can *any* Mk4 cluster get VSS via CAN? Or is it just later ones with Mk60 ABS modules? I'm not real sure Mk20 modules like my 2001 Golf have will broadcast VSS via CAN. Not to mention, it is the older immo II cluster.

I have seen coding in BEW clusters to pick up VSS via CAN, but have not seen that in ALHs.

 

[Matt-98AHU]

Part 2 is up. Tearing it down, kind of fumbling through figuring out how differently I have to approach getting 5th and 6th gear assemblies off vs what I'm used to on the 5 speeds.

Edited the original post with the new video, also posting it here:

 

[dieseldonato]

This is great, one of my biggest issues with my 01 is dealing with hills and 5th being too tall and 4th too short. Following with keen interest.

 

[Matt-98AHU]

This is great, one of my biggest issues with my 01 is dealing with hills and 5th being too tall and 4th too short. Following with keen interest.

I feel ya. I put a 0.658 5th in my '01 Golf and on some drives in the mountains, certain uphill grades, get caught with traffic going just slow enough where the taller 5th gear is now too tall, but 4th gear is too short. Having the in-between will be REALLY nice.

 

[Matt-98AHU]

Pinion shaft has been stripped.. that video will come later today. I've taken measurements and left it with a machine shop that's literally next door. I left them with a 02J pinion shaft as well so they could measure it themselves and compare.

Looks like 2 mm length needs to be taken off the short end of the pinion as well as 1 mm diameter in order to accept the 02J small pinion bearing as well as not have any interference issues with the case itself.

I measured from the base of the pinion gear to the end of the shaft as being 17 mm on the 02S, and 15 mm on the 02A/J/earlier 0A4.

30 mm diameter on the 02S, 29 mm on the 02A/J/earlier 0A4.

Once again, the 0A4 starting sometime in 2018 production changed the pinion bearing to be the same as what I'm seeing in this 02S. So, there's a lot of 0A4s from 2005 through 2018 that just use the same bearing there that the 02J/02A uses...

I should have the pinion shaft back tomorrow. In the meantime, going to extract the ring gear from the diff for a Wavetrac install, can also at least get the old bearing races extracted from the 02J case and new ones installed.

I may stay a little after work tomorrow and do that plus get new bearings on the input shaft, swap the ring gear to the Wavetrac, install the speedo gear and press on the diff bearings. Check bearing free play without shims, shim accordingly, friction torque double check the diff bearings, call it a day.

That will leave me just with having to get the pinion back from the machine shop tomorrow, press on its new bearings, measure for and then install shim size for pinion preload, friction torque double check it, adjust further if need be, then start final assembly. Get the gear stack back on, get everything installed in the case, case halves re-assembled, sealed, torqued, then install the 5th and 6th gear components, rear cover, new seals, axle flanges and call it done... Then play the waiting game for me to find the time and weather window (only have an outside space to work with on the car at the moment) to get the transmission installed.

 

[Matt-98AHU]

Part 3, stripping the pinion shaft, added to the original post.

 

[turbocharged798]

As far as the VSS over CAN, I believe its only available on the late MK4 clusters with the 503MH software(the ones that chime over and over if your seatbelt is left off. It also requires EEprom editing to turn it on. I haven't experimented much with it but it appears to be possible.

Bummer about machining the shaft for the smaller bearing, otherwise it would have been almost bolt in. I built a custom 02J using a gasser case and CTN 02A internals to get the 3.16 R&P and I actually find 5th gear too tall now and find myself constantly dropping to 4th. Watching this with close interest.

 

[oilhammer]

Out of curiosity: I know this would possibly vary with modifications, but has someone given thought to what the "ideal" RPM for the ALH is when cruising? I regularly am at around 3000 RPM, with squirts to over that, which isn't a problem but obviously the fuel economy suffers. I feel like anything under 2500 at 80 may be TOO low, but.... ?

 

[jeffecor]

The only thing that's also really off about these is the bellhousing does space the transmission a little further away from the engine. If I were to get a good shot of where the casting for the axle flange seal on the passenger side is vs. the bellhousing where it meets the engine, you can see on the 02J it's completely flat. The 02S (and 0A4) space the gearbox a little further back. mk5 and up cars are technically supposed to have a different flywheel that has additional offset to correct for this.

This spacing also means if your current drivetrain alignment has the transmission mount bolts in the slotted holes in the transmission mount are already more towards the driver side, the 02S would push it even further still to the driver side.

And can *any* Mk4 cluster get VSS via CAN? Or is it just later ones with Mk60 ABS modules? I'm not real sure Mk20 modules like my 2001 Golf have will broadcast VSS via CAN. Not to mention, it is the older immo II cluster.

I have seen coding in BEW clusters to pick up VSS via CAN, but have not seen that in ALHs.

The eeprom vss edit was available in the mk4 later clusters here's information on the editing of the cluster eeprom.

Tuner Pro XDF for VAG VDO Clusters VWK501HM & VWK503HM

Tuner Pro XDF for VAG VDO Clusters VWK501HM & VWK503HM

nefariousmotorsports.com

Also, I was able to swap a newer cluster from 2002-2003 into my 2000 Jetta and I was able to read the abs speed too. My newer Jetta wagon's 2001 and 2003 was able to read abs speed too with the switch of the eeprom code.



I was reading up on clutch's for solid mass on Idparts. They are listing the alh, bew and brm use the same solid mass clutch kit.

Sachs G60/VR6 Clutch & Flywheel Kit (A4)(A5)

Sachs VR6 clutch kit mated with an IDparts 21lb, G60 single mass flywheel. This clutch will fit all A4 or A5 Jetta TDI, A4 Golf TDI and New Beetle TDI. This clutch includes a new single mass flywhe...

www.idparts.com

I while back in 2018 we had BRM that I manual swapped to 02j parts listed below. Also, there was no issue and sold it last year.

Mk4
ALH 02J with mk4 trans mount
ALH flywheel/ clutch
Shifter and cables

MK5
BRM starter
2.0 manual axles
Upper trans mount and lower

 

[dieseldonato]

Out of curiosity: I know this would possibly vary with modifications, but has someone given thought to what the "ideal" RPM for the ALH is when cruising? I regularly am at around 3000 RPM, with squirts to over that, which isn't a problem but obviously the fuel economy suffers. I feel like anything under 2500 at 80 may be TOO low, but.... ?

I think this would vary with mods/tuning. No matter how you stack it, they were geared to spin a lot of rpm when going higher speeds to make up for the lack of power under 2k rpm. With my current tune, injectors and turbo I'd be happy with 80mph @2500 rpm.

 

[Matt-98AHU]

Out of curiosity: I know this would possibly vary with modifications, but has someone given thought to what the "ideal" RPM for the ALH is when cruising? I regularly am at around 3000 RPM, with squirts to over that, which isn't a problem but obviously the fuel economy suffers. I feel like anything under 2500 at 80 may be TOO low, but.... ?

ALHs are perfectly happy cruising at 2200 RPM, at least with a stock-ish turbo. I've gone up mountain grades maintaining 70-80 no problem with a 0.658 5th. The challenge comes when traffic forces you to slow below 65 on uphill grades and the engine really starts to lug as you drop to under 1900 RPM. But then downshifting to 4th feels almost too short, which is why the 6 speed conversion I have here makes me feel it would be a nice happy medium.

Before I found out about these specific 02S boxes, I was getting close to pulling the trigger on a used 0A4 5 speed from a 1.8 TSI, which has a 3.39 R&P still, but has slightly taller 3rd, taller 4th and 0.66 5th. So, just is better spaced gearing for the taller 5th.

I think if I did a MK3 or older custom MQ250 at this point, I'd likely opt for that 1.8 TSI 0A4 gear stack, and put it onto the Mk3 TDI 3.16 R&P. Plus, those are lighter weight cars, I feel the wider spaced gearing would feel just fine on them.

But, there apparently does exist a 02S in Europe with a 3.16 R&P. Some oddball A3s got them, but they're likely much harder to find than the 1.4 TSI North American boxes I just got.

 

[Matt-98AHU]

Yesterday was differential day. I compare diff bearings from the 02S/0A4 vs. what 02Js and 02As normally use. I extract one bearing on the original diff just to see if the Mk4 VSS gear will drop onto the 02S diff (spoiler: it doesn't!).

Drilled out the rivets that hold the ring gear to the diff, chiseled then out, pressed the ring gear off, got the transmission guts send through the parts washer, installed the ring gear onto a Wavetrac 02J-B diff, installed my speedo gear and bearings.

Disassembly and comparing some things:

Assembly:

 

[Updatelee]

Im running an 02Q six speed on my ALH, rewrote the cluster for ABS over CAN instead of VSS, it works well. So much easier then drilling out your case to install a VSS sensor you really dont need. unless Im missing something here

 

[oilhammer]

I guess my question was, if we agree the gearing for fifth is too short for those of us that spend lots of time at 80+, then what would be TOO tall if say you had to cruise at 65 or 70 due to road conditions and/or local law enforcement fund raising events.

I agree I think 2200 is about as low as I'd want to spin the engine at highway speeds.

 

[Matt-98AHU]

I guess my question was, if we agree the gearing for fifth is too short for those of us that spend lots of time at 80+, then what would be TOO tall if say you had to cruise at 65 or 70 due to road conditions and/or local law enforcement fund raising events.

I agree I think 2200 is about as low as I'd want to spin the engine at highway speeds.

I've cruised at 55-60 in 5th gear with the 0.658 just fine. It's only if you need to accelerate or go up an incline where you really need to downshift. But for cruising? The taller gears are still great.

Personally for me, if it's only going to have 5 gears, I don't think I'm going any taller than 0.658. And that's what attracted me to the 1.8 TSI gearing that also has taller 3rd and 4th, so the gap between gears isn't so huge and its original 5th is a 0.66 (tiniest, unnoticeable hair shorter than 0.658).

 

[Matt-98AHU]

Im running an 02Q six speed on my ALH, rewrote the cluster for ABS over CAN instead of VSS, it works well. So much easier then drilling out your case to install a VSS sensor you really dont need. unless Im missing something here

If only it were drilling out the case! This is getting the case swapped, so all the bearing tolerances need to be redone.

I suppose for me, I just like this architecture better than the twin pinion shaft setup. The clutches and flywheels are much cheaper and readily available. The synchros don't crack when you swap to a single mass flywheel.

Twin pinion shaft MQ350s are better for big power, for sure. They are indeed stronger.

Would be great if one of the people who keep mentioning the ABS over CAN modification could post a nice how-to or a link to one.

Part of my making this video is also for anyone interested in rebuilding any gearbox in this transmission family. Plus, a part of me was just also curious, as I had not had my hands on a Genuine VW 02S before. I've installed two Eurotuning kits for people as add-ons to their original 5 speed box, and I've taken apart and repaired a couple of the 6 speed add ons Cascade German had briefly. So, yeah, I was just kind of curious to see how the genuine VW versions are setup. But yes, this is clearly a much, much more involved process than most transmission swaps.

Sometimes I don't ask myself if I should do something or if it's reasonable or easy to accomplish... I just do it because I get a weird idea and I just have to go for it. At the same time, I've taken a ton of MQ250 boxes apart to repair, put fresh bearings into, check and set preloads etc, and aside from the fumbling around figuring out the extra gear situation, these are pretty easy to work with.

 

[oilhammer]

I feel the same way sometimes... like when I put Bosch L-jet on a Mazda engine in a pickup.

 

[Updatelee]

My cluster is 1J5920826C and the address for ABS instead of VSS is 0x65, value 0x80 = VSS sensor, 0x83 = ABS sensor

My ECU is 038906012GN and the address for ABS instead of VSS is 0x51BBA, value 0x01 = get speed from the cluster (VSS sensor), 0x03 = get speed from ABS sensor