Some background: My car is a BAT 01 A4 Avant with an AWM 1.8t that is making close to 400AWHP. I saw full boost (25psi) at ~4800 RPM with the 01A. The reason I swapped a 6MT into my car is I had already blown up 2 5MT and wanted a transmission I could drive without worrying about breaking. So I used an 01E out of a 01.5 B5S4. I bought the trans used with 100k miles with the linkage and mounts for $800, which is a fairly low price. Most 01Es that don't require an immediate rebuild are around $1000, but you can score ones needing a 1-2 syncro or shift collar for around $4-500. The 1-2 syncros breaking and shift collars are common problems on 01Es.
First things first, is this transmission suitable for a 1.8L 4 cylinder engine?
This is the most asked question I have noticed when researching the swap. Having driven both now, around town and on the highway, I feel I can shed some light on the subject It isn't the ideal transmission, simply because it was meant for an engine that produced more torque than our 1.8Ts can, ie the 2.7t. Because of this, 1-3 gears are slightly taller, and 4-5 are slightly shorter. HERE is a thread that discussed the gearing of various transmissions, both 5- and 6-Speed.
The gearing is not really noticeable in first gear, but I did notice a slight difference when driving around town in 2-3. It is not bad to drive at all, and with the shorter 4.11 final drive vs. the 3.89 of the 5 speed, it really doesn't struggle to accelerate at all around town. On the highway, it drives pretty much the same, but there is more shifting necessary to keep it in the powerband, but that is with any BAT car really. At 85mph, the engine is turning at 3500 RPM, a drop of about 500 RPM from the 4k RPM with the 01A. I did notice an increase in gas mileage on my 252 mile trip to school, averaging about 22 MPG with 630cc injectors and tune. That was not all just cruising either, as I did multiple pulls and a tunnel blast.
Now that you've decided you want to get rid of your 5MT and swap in the much stronger 6MT, you'll need to gather your necessary parts. Depending on what year your car is dictates what parts you will need, and there are several options to take. There are several differences between the 5MT and the 6MT that need to be addressed before the swap can be completed. The option that I took is the easiest and the cheapest, IMO.
I'll break it down into the problems that you will face during the swap, and solutions to them depending on which car you are swapping into. The first thing to consider is:
Mounts
- If you drive a V6 A4, then you will be able to utilize the stock 01E mounts, since you share the same subframe as the S4.
- If you own a 1.8T A4, then you run into the problem of their subframe using a different style mount on the drivers side. To solve this problem, you can either:
- make your own bracket for the stock 1.8t mount
- cut the 1.8t mount off the subframe and weld in the V6 bracket
- swap subframes
Since my car is a 1.8T, I had to do something about my drivers side mount. I chose to make my own bracket for the mount since I had an 034 Street Density mount there already.
Axles
The S4 uses a 108mm inner axle flange rather than the 100mm flange that the A4s use. To make this work, you can:
- Swap 100mm flanges into the 01E, but the ones from the 01A do not fit. Where can you find 100mm flanges that will fit into the 01E? The stock rear diff. They bolt into the diff using a hex head bolt, just like the 01E. So remove the screws, swap the flanges, and put the bolts back in. MAKE SURE YOU KEEP THE BOLTS WITH THE FLANGES. The 01E flange bolts will not work with the A4 diff cups.
- Swap in the front axles from an S4. To do this, different parts are needed depending on the year of the car.
96-00 A4 1.8t
- S4 Axles
- S4 Uprights & Hubs
- S4 ABS Sensor
01 1.8T & 96-01 V6
- S4 Front axles
Since the 01 1.8T and V6 A4s all have the same larger outer CV Joint as the S4, no uprights are needed to swap in S4 axles.
Rear Diff
Because the final drive of the 01E is different than the 01A, the rear diff has to be changed. There are two differentials that will work, both have the code DAK:
- S4 Rear Diff
Direct bolt in, requires use of S4 rear axles or swapping of the diff flanges - Tiptronic A4 Diff
Direct bolt in, uses stock A4 axles
Driveshaft
The 01E is a few inches longer than the 01A, so a shorter driveshaft is needed. There are not many ways around this, you either have to use a S4 unit, or a aftermarket 1-piece unit made for the B5S4.
Shifter
The 01E shift rods can be used with any shift box in the car, but the 5MT shift boxes will NOT have a reverse lockout. The H-pattern isn't exactly nice, since I think the pivot ball on the 6MT shift boxes is moved slightly to the left.
Other Issues
I started a different thread asking whether or not I would have clearance issues with my CM FX400 240mm clutch/FW combo. The answer is there is no clearance issues and the cranks spins without issue when the transmission is bolted down.
EDIT: I found out this is not actually true. My fx400 disc was rattling, so I pulled the trans after about 5k miles. The CM flywheel/fx400 combo rubs the bellhousing ever so gently. Not enough to make a terrible noise, but enough for there to be marks before it self clearances. I have included a pic below. I simply removed slightly more material using a die grinder. Re-installed everything and haven't had a problem since.
The route I chose consisted of swapping the trans, driveshaft, and diff. The diff I got from an automatic A4 so everything else is stock A4. Because of this, I was able to complete the swap for just $1100.
- Trans - $800
- Driveshaft - $100
- DAK Rear Diff - $200
I am currently using my 01A shifter but plan on swapping in a 6MT very soon, and they are very inexpensive.
That's pretty much it for now, if I come across any relevant pictures I'll edit this post and add them in. I have a few pictures of my swap, but I just need to get them off my camera. If anyone has any info to add, post it up and I can either add it to the first post, or at least it will be in the same thread if someone is searching.
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Originally Posted by lorge1989
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