duane

What if any are the differences among these three transmissions besides the final drive ratio? How interchangeable are they? Thinking of changing an auto 87 S4 to a manual.

Thanks!

Andre Hedrick

I spoke with Mark A, last thursday and pitched the same question. There is no notable difference other than pure strenght of the box. Most people do not need the rare G28/13 or G28/55, the 10/11/12's share the same syncros and shifting characteristics desired, on the 13/55's are beefyer (sp). Mark's reason to me for using the tougher 13 v/s the available 10/11/12's was he kept breaking 3rd gear with "RACING". There is a several thousand dollar difference and a longer waiting list to find a 13/55.

Cheers,

John Veninger

How is the 13 stronger than the 12?
The 12 is a S4 Euro trans and 89 only US with a 2.64 vs the 13 is only an 87-88 US trans w/ a 2.20.
Thought Mark used a 57 and Joe F. used the 55.

Andre Hedrick

John,

DOH! I will have to ask Mark A to educate the dunce from NorCal, again.

So the 10/11's and the 12/13 differ?
What in the world is a 57?
Or is the 55 LSD and 57 os PSD?

marton

all manual boxes have the same external dimensions; except the later ones which are a couple of mm wider at the half shaft connection.

The late & post 86 boxes have a better and stronger synchro design.
If the box comes complete with rear end then the final drive ratios may vary.

It is rumoured that the GTS boxes are stronger but exactly "how" I do not know

Marton

Andre Hedrick

I thought the 55 was the GTS box? The difference was the GT/GTS has an external oil cooler for the tranny?

Note to self again!

FlyingDog

55 is GT. 57 is GTS. 89GT trannies have stronger straight cut ring and pinion. GT and GTS trannies have harder/stronger gears.

IIRC, 12/13 have wider gears than 10/11.

John Veninger

GTS 5 speed changes:

John Veninger

Anyone have a spare 57 for sale

Vilhuer

To put it simply:

10 and 11 = '85-86, only difference between two is gearing
12 and 13 = '87-89, larger and stronger input shaft bearing and some other more minor changes
55 = GT, stronger again, '89 with LSD and '90-91 with PSD
57 = GTS, see John's list

All are good enough for normal use.

John Veninger

The 55 has 2.73 gears. LSD in 89, PSD in 90-91

Vilhuer

12 = 2.64 and 11/13 = 2.20, LSD optional on all three.

It is strange Porsche didn't change G28/55 to some different number when PSD was added. Casing is different because of it and all.

John Veninger

Maybe Hans though it was quicker just to hold the #5 to stamp the 55 vs picking up the #6 for two years