4K vs 7A...should i?

[rabbit gti guy]

Ok so im in need of getting my tranny rebuilt...its leaking fluid out of a few seals and it doesnt shift good anymore.   Im pretty sure it needs 2nd and 3rd gear syncros...at the least and new seals.   Anyway...i found this 4K tranny...with a Quaife LSD in it.   The guy also swapped the 5th gear to 0.71, which is the same as my 7A right now.

I checked into the gear ratios, and as it sits the final drives are the same, as well as first and fifth.   the only diff is that on the 4K the 2,3 and 4th gears are a hair shorter...

my question is do you think i should run the 4K or should i look for a longer ratio tranny?   I like the 7A right now, as its fine on the highway, and i dont mind shifting.   im looking to up the boost and fuel eventually, and dont know if i should switch to a longer ratio.

what do you think?

[Quantum TD]

I presume that you're talking about a MK I Rabbit TD? The 7A and 4K only came in Rabbits originally.

I'd stick with the 7A. It's a pretty rare transmission, and it's perfectly suited for the 1.6 diesel. I'm not sure why VW didn't put that trans in all of their 1.6 diesel cars (or at least the 1.6 ones). It's perfect for acceleration and cruising on the highway.

I've personally tried the 4K on my 1982 Rabbit 1.6D (NA). It was the worst. I was in 5th gear by the time I hit 45 MPH. My max speed was only about 55-60 before I feared damage to the motor due to high RPMs.

I'd venture to say that even with the .71 5th gear, it would be a bad idea. You'd have a huge gap to fill between 4th and 5th gear.

Good luck.

[vanagonturbo]

The 7A and 4K only came in Rabbits originally.

Not correct. In the US, the Cabriolet (rabbit convertible), Scirocco, and the Jetta GLI got the 4K. In '83 the above mentioned cars also got the 2H. The 7A only came in Jettas, Rabbits, and no Cabriolets or Sciroccos. Just an FYI.

Like he said though, stick with the 7A. I am swapping one into my Scirocco next weekend. I have all the other options available to me but I will be using the 7A with 100mm joints and an LSD. Should be a good upgrade from the FF thats in there now.

[Quantum TD]

Not correct. In the US, the Cabriolet (rabbit convertible), Scirocco, and the Jetta GLI got the 4K. .

Perhaps. I've never touched a 1984-older Scirooco (fugly and uncomfortable, save for the pre-1982 Scirocco), a Cabriolet (gay as the day is long), or Jetta (as rare as hens teeth in the US). I do know however that the 4K was popular on the 1984 GTI.

Regardless, in my mind, the 7A is the best trans (in terms of gear ratios and final drive) for any 1.6 application (turbo or otherwise), if you want fuel economy. The FF is a nice second choice as vanagonturbo notes, but the lower final drive means poor torque at low speeds (i.e. crap acceleration).

I guess our final verdict (if I may speak for vanagonturbo) is that the 7A is worth saving and is the best fit if you want readily available torque and low RPMs at higway speeds (i.e. best fuel economy).

[rabbit gti guy]

7A - 3.94 final drive      3.45 1.94 1.29 0.91 0.71
4K - 3.94 final drive      3.45 2.12 1.44 1.13 0.71 (0.89 stock)

i know the tranny is "rare"...but i dont see too much of a difference in the gearing...i like the short ratio...i dont mind shifting...is there really that much of a difference?

plus the quaife LSD doesnt hurt either

[somolovitch3]

As an owner of both an 81 Caddy and an 84 GTI, HELL YES!

The Caddy will cruse at 65 mph very nicely, while the GTI is making 4000 RPM to do the same. Of course, one is a Diesel, and the othe a gasser, but let me tell you...I am looking for a different trany for the GTI.

Oh its great for to go whipping thru downtown trafic, just don't get on the freeway! Yea when you can shift from 1st to 4th and hardly notice it....... :roll:

Any one know of a taller geared trans out there?

tia