ALH Golf Trans to BEW Jetta?

[hyoung319]

Can you put an ALH transmission into a BEW Jetta? My BEW is automatic which of course quit on me. I have a manual ALH sitting and was wondering if the swap is possible.

 

[Shenandoah]

hyoung319,

I'm sure others will comment, but as far as I know, the manual transmissions from the ALH and BEW are the same. In my Audi TT -> TDI conversion I put an ALH motor paired with a manual transmission from a BEW. Everything matched fine.

Eric

 

[oilhammer]

The BEW's version of the 02J is geared slightly taller, but other than that, they are essentially the same as what was used in the ALH. Keep in mind, the ALH cars through 1999 style used a version of the early (crappy) style shifter like the A3 platform cars used. So you don't want that.

 

[GlowBugTDI]

The BEW's version of the 02J is geared slightly taller, but other than that, they are essentially the same as what was used in the ALH. Keep in mind, the ALH cars through 1999 style used a version of the early (crappy) style shifter like the A3 platform cars used. So you don't want that.

So technically you could swap out for a bew trans and increase mpg?

 

[hyoung319]

So technically you could swap out for a bew trans and increase mpg?

I would just like to say if you were to do that definitely do not go auto. Tiptronics are by far the worst.

 

[Matt-98AHU]

So technically you could swap out for a bew trans and increase mpg?

Sort of... except the 5th gear is such an infinitesimally small difference that most people don't even notice.

0.756 5th vs. a 0.744, effectively.

2600 RPM on the 0.756 5th is about 75.18 MPH.

2600 RPM on the 0.744 5th is 76.39.

I did the math on the difference when going exactly 75 MPH... it's about 42 RPM (2594 vs 2552 at 75.01 MPH for both).

You're going to need a noticeably larger difference in RPM than that to make a noticeable dent on MPGs.

 

[oilhammer]

It is about 100 RPM difference at 80, so not a lot. And I am not sure I notice any real difference in MPGs. I only used a BEW 02J in my ALH because it was a '99.5 and I was swapping over the craptastic "wooden spoon in a bucket of marbles" shifter setup. And I had the whole trans, so I figured "why not?"

You'd have to swap in one of the taller 5th gear sets available, and unless you only drive the car at high speeds, I am not a huge fan of that. Because the 4-5 gap increases enough that I feel like I am lugging the engine too much trying to use 5th at around 45-50 MPH, so I would tend to use 4th more, in which case any fuel savings would be a wash.

But if you cruise long distances at a steady 70+ as a primary use, then yeah the taller 5th is great.

 

[Shenandoah]

The 5 speed manual in my Audi TT -> TDI was originally in my 2005 BEW Beetle. When it was in the Beetle, I put in a .658 5th gear as I was commuting about 60 miles (highway driving) a day. Later, I put a 6 speed manual from RyanP in my Beetle.

When I did the TDI conversion on the Audi TT I picked up for cheap, I put the 5 speed manual from the Beetle in with the ALH as the 5 speed gas Audi transmission wouldn't have been geared right for the ALH. As Oilhammer mentions, it's a big jump from 4th to 5th with the taller .658 5th gear. For the most part I do not shift in to 5th unless I'm on the highway or going over 60 mph. With the .658 I'm turning about 2500 rpm at 50 mph, just under 3000 rpm at 60 mph.

EDIT: my rpm values while in 4th gear were incorrect above. Here are the correct values while driving in 4th gear: At 50 mph - 2250 rpm; at 55 mph - 2500 rpm; at 60 - 2750 rpm


Eric

 

[Matt-98AHU]

It is about 100 RPM difference at 80, so not a lot. And I am not sure I notice any real difference in MPGs. I only used a BEW 02J in my ALH because it was a '99.5 and I was swapping over the craptastic "wooden spoon in a bucket of marbles" shifter setup. And I had the whole trans, so I figured "why not?"

You'd have to swap in one of the taller 5th gear sets available, and unless you only drive the car at high speeds, I am not a huge fan of that. Because the 4-5 gap increases enough that I feel like I am lugging the engine too much trying to use 5th at around 45-50 MPH, so I would tend to use 4th more, in which case any fuel savings would be a wash.

But if you cruise long distances at a steady 70+ as a primary use, then yeah the taller 5th is great.

Fun tidbit I found out recently:

There are a couple 0A4 transmission codes from Mk7s with 1.8TSIs that have taller gearing than Mk4 TDIs.

Same 3.39 final drive, slightly taller 3rd gear, a 0.84 4th instead of the 0.9something the TDIs have, then a 0.66 5th.

Would be a great upgrade for a BRM being that it's the same transmission family, so the shift bracket fits and all.

I personally would love to use the gears themselves in a Mk4. It at least somewhat addresses the huge gap between 4th and 5th when you just swap on only the 5th gear on a standard TDI transmission.

Still a largER gap than the standard TDI transmission, but not near as bad as just swapping a 0.658.

 

[dhangejr]

One sily lesson i learned...

basically the difference between the BEW and ALH 02j trans' is the ring gear size.

o2js < 2004 have a 114mm ring gear inner diameter

The 02J > 2004 are 113mm ring gear

it only matters if you are re manufacturing the trans tho...

 

[oilhammer]

The NCS 2.slo Jetta S 5sp, which I am not sure which it is, but it is not the same as the 02J, is geared really tall, too. Which makes those cars really feel sluggish around town, but they are not too bad on the highway, and light years better than the old 2.slo cars that would scream 4k at highway speeds.