Parts for a 1.8t 4motion B5.5 to TDI conversion?

[Spring1898]

Assuming I have a donor car of 6 speed Manual converted FWD B5.5, and a stock 1.8T manual

What else is needed for conversion?
Different Rear Diff?
Different (AWD capable) Trans?

Trying to get an idea before I pull the trigger on a 1.8T manual...

 

[mogly]

Technically the 4-motion car doesn't need to be a manual although it does simplify the swap so a degree.

You'll either have to purchase a diesel 4 motion tank or modify the opening and add the diesel pump unit. TDI Trans and differential. I've not done the swap in a 4 motion car but I presume the coding can be altered so the ECU knows the car is 4 motion. The exhaust is 4 motion specific. You might be able to run the fwd downpipe and make your own system.

 

[PickleRick]

You don't necessarily have to install the TDI fuel pump bucket, you can install a return TEE to bleed off the excess fuel pressure back to the tank.

@vwztips is the only person I'm aware of that has successfully done a clean, factory looking/wired 4 motion from an original gasser. I'm not sure if he did a build thread or not. Hopefully by tagging him he will respond


Frans can likely get you the transmission, rear diff and drive shaft that you need along with clutch/shifter assy.

 

[caffeine]

Modifying the filler neck is way easier than buying and swapping in a diesel fuel tank. The FWD diesel pump will drop into the 4motion sending unit without too much trouble, and the FWD fuel line assembly can also be swapped over, just cutting one of the hard lines short on the tank end (line assembly has a sort of cooler built in as well). Personally I think it's better to swap out the pump rather than put a tee in the fuel lines, as you'll end up with more consistent pressure to the tandem pump, and there will be no possibility of over-pressurizing it.

The 6-speed from the FWD car will not be usable in a 4motion car, but the clutch can be reused. Easiest transmission to use would be to get a 5-speed 4motion diesel transmission from Europe with a matching rear diff. If using a 6-speed diesel transmission, the driveshaft will also need to be imported, unless you can find a very rare factory W8 6-speed manual driveshaft here in North America. Another transmission option is the GVE 02X 6-speed manual from a B7 2.0T car, which would work with a factory auto 4motion driveshaft. Gearing isn't as long as a diesel transmission, but they're pretty commonly available, and gearing is still fairly good. Using the 02X comes with a couple other necessary modifications (like a custom trans mount solution).

Depending on what transmission you go for, and what transmission the donor has, the 6-speed shifter from the donor may be usable or the 5-speed shifter from the 4motion car may be able to be reused.

The factory 1.8T transmission will bolt up, but fuel economy will suffer considerably because of the gear ratios.

Aside from that stuff, and some wiring (year of the 1.8T car will determine how involved the wiring is), most other stuff is pretty self-explanatory, especially if you have the full diesel donor to use. Swap the cluster and lock cylinder from the donor to avoid any immobilizer issues. Since the donor already has a manual conversion, you may not need a tune at all (ECU does not care AWD vs FWD since the AWD system operates entirely mechanically). The one thing that may cause issues is if the 4motion car has ESP and the donor does not. If the 4motion car has ESP and the ECU isn't compatible with that, the ABS/traction control light will be permanently on until the ECU is tuned for it. Either way, the ABS module will need to be coded with VCDS to communicate with the diesel ECU.

 

[GTiTDi]

Unless the 1.8T is junk I wouldn't bother. They can last 250K miles without major issues and make plenty of power with reasonable fuel economy.

 

[PickleRick]

Unless the 1.8T is junk I wouldn't bother. They can last 250K miles without major issues and make plenty of power with reasonable fuel economy.

Blasphemy!!!

 

[GTiTDi]

Blasphemy!!!

hey, would be a great gasoline powered ride for our ever fluctuating fuel pricing and threats of "diesel shortages"

 

[oilhammer]

I agree the AWM is a pretty good engine, but "reasonably good fuel economy" is probably not their strong point. While my 2004 4Mo wagon is still kicking along just fine at nearly 260k, it gobbles premium gasoline to the tune of about 22 MPG average, and that's mostly highway. RC1 helped it get out of its own way, but it doesn't have the punch the BHW does and its gearing is so short it uses all the tach to get the job done. Mine's a slushbox, so that certainly doesn't help. B5s are heavy. 4Mo B5s even heavier.



But boy when it comes to blasting through the snow.... it is a hoot!

 

[PickleRick]

Doesn't the 1.8t require high test? The only gasoline I purchase is sub 5 gallons a week to run a genny for ac/coffee on the lake every weekend and occasionally my JD mower. I never bother to look at the price since I get so little


The little lady has to put the good stuff in her disco so I hear her screaming on a regular basis when it exceeds 3.75 a gallon

 

[oilhammer]

"Premium" = "high test", yes. And yes, it does require 91 octane. If you run regular, you'll notice right away, because the ECU will retard the timing as soon as it detects an input from the knock sensors, which happens pretty much the very first time you accelerate on that key cycle. If you listen carefully, you'll even hear that slight detonation before the ECU pulls it back. It is pretty obvious, especially in the heavier Passats.

 

[pro51492]

I just stumbled upon what seems to be a 2004 1.8T 4 motion wagon with a manual that has been converted to a BHW it shows gas via auction search but I know a BHW when I see one. I pulled the trigger and bought it. The car seems super clean but have not seen it in person. Might have been a former members car, I can’t imagine that many of these are floating around.

IMG_0145.jpeg

• pro51492
• Oct 4, 2023

04 B5.5 4 motion BHW

IMG_0149.jpeg

• pro51492
• Oct 4, 2023

04 B5.5 4 motion BHW

 

[GTiTDi]

I agree the AWM is a pretty good engine, but "reasonably good fuel economy"
about 22 MPG average,

Well I'd say the slush box has EVERYTHING to do with that poor mpg figure. Overall load the vehicle deals with has a lot to do with it too. One customer with the cleanest 04 b5.5 awm 4motion 5spd around here says he sees a low of 28, but he is a little old man. The others I see are ratty comparitively, and the owners couldn't be bothered with figuring out their mileage.

 

[oilhammer]

Even my manual FWD AWM sedan I resurrected and owned for a minute wasn't going to break 30. I think the general low gearing that most VAG cars had during that period, manual or automatic, took a lot out. The newer stuff they have geared up considerably. But then on certain applications, like the 2011-2015 NCS Jetta S, with the standard 115hp "2.slo", they feel somewhat sluggish off the line and around town. But they'll cruise nicer down the highway.

I think (I know) I'm just spoiled by the diesels. I drive 100 miles a day, it would be a lie altering thing to drive something that got less than 40 MPG every day, although the fuel price per gallon offset obviously makes a ~35 MPG gasser that is happy with regular gasoline certainly an alternative.... but then there really are not any that I'd generally WANT to drive.

I honestly feel the ALH+ manual Golfs check all the right boxes for me as a daily driver. They look good, they fit good, they drive good, they are well known and easy to service, easily modified with little if any downsides, and they hold up well. I dare say I'd rather drive my 613k+ mile 2000 Golf over my wife's brand new 2024 Mini Cooper. The Golf is bigger, faster, and uses less fuel.

 

[PickleRick]

It's hard to imagine a 1.8t wagon 4motion getting 30 plus mpg. The fuel sipping 94 accord wagon only got north of 30 if you did drive like an old man on the freeway.

 

[oilhammer]

I don't remember what the EPA MPG estimates were for the gas Passats at the time. The BHW was 38 hwy, and that's pretty much on par with what ours has always gotten. For some reason 31 sticks in my head, but I cannot recall if that was manual or automatic, but I seem to think it was the manual, because that was what I was comparing as I'd never willingly purchase something with only two pedals if I'd had the option of not doing so. And the AWM cars were indeed available here with manuals, but all the BHWs were automatic.

I have owned four AWM B5s; a manual FWD sedan, an automatic FWD sedan, an automatic FWD wagon, and the 4Mo automatic wagon I have now. None of them could ever break 30, but the manual sedan could probably come close. I of course do not drive for MPGs, so there's that.

Worst [modern] dub ever that I had for a bit was a 2002 automatic 2.slo NB. It's hard to stomach how much gasoline that thing could consume. I don't think I drove it enough or through enough tanks to get a good average, but I know I did with my 2005 2.slo which was a manual, and that got about 27, and the 2002+auto was much worse. It may have been down around 21 or 22. They're that bad.

I realize at the time VAG probably had little need to have a fuel-sipping gasser in light of the superior diesels available alongside them on the dealer lots, but they did have 1.6L 75hp gassers available in Europe that probably were not as thirsty (although they would have likely been deemed too slow for the American market.... but they sure sold plenty of Golf 4s in Europe so-equipped).

 

[Mozambiquer]

My current daily driver is a 1.8t awm fwd 5 speed passat wagon. I average about 23-25 mpg running 91 octane. Not as bad as my W8 auto did, but not a lot better.
It's fun to drive though, so there is that.

 

[Spring1898]

Sounds like I am better off waiting a couple more years until we can import them direct from Europe.
Maybe we should get a 'group buy' container ship, lol

On a semi-related topic, did the Jetta ever come with 4 motion and a 1.8T?

 

[adamss24]

The Octavia was offered with AWD, 5 speed gearbox and 1.8t 150bhp…rare sight though !

 

[Zak99b5]

In one of my old Passat wagons (AEB 1.8T, manual, fwd), I could get close to 30 on the highway, according to the MFA of course. Hand calc was always a little less, but not that much.

On my other Passat AEB wagon with a tiptronic it was more like low-mid 20s.

My AEB Audi A4 avant quattro, manual, also got low-mid 20s. It was also Unitronic chipped. The jump from 150 to 200 hp was astounding. Fun car.