Oddjob

The S2 and Turbo trans cases and gear carriers are the same. The bearings and gear sets 1-4 and reverse are the same parts.

In basically all respects, the S2 and the Turbo/Turbo S transmission are identical except for the R/P and 5th gear. So if you have an S2 trans with a Turbo 5th gear, its the same as a Turbo trans with an S2 R/P (this sounds much more confusing than it really is).

You can do the same with an 87-88 944S transmission. Put a Turbo R/P one of those - boom, you have a Turbo trans. Put in an S2 R/P and a 778 5th and you have an S2 trans.

There is no point in pulling the S2 R/P to install in a Turbo box, its the same thing. Depending on what 5th gear you want, use either the 829 or the 778. It is so much easier to swap 5th gears than it is to swap and setup a R/P. If you are pulling 155mph at a track, I would leave the S2 778 5th in the car. The 829 Turbo 5th would be a couple ticks into the redline at 155 mph.

Of course trans accessories can come into play with these decisions, i.e. LSDs and Oil Coolers. If you have an open diff S2 trans and a LSD oil cooled Turbo trans, then its kind of a toss up, which to use and which to borrow from (swap the S2 R/P into the Turbo case, or swap the LSD and oil cooler components into the S2 case)....

Footnote: The S2 does use the later Turbo S input shaft (so it also has the harder 1st and 2nd gear teeth). And the S2 LSD is the same as the Turbo S LSD, which has some slight changes versus earlier 951 LSDs. But I will argue that these upgrades are not that significant, and do not dramatically improve the strength and life of these parts.

special tool

I agree with oddjob 100% on the gearing, as usual.
The only thing to consider with reguard to S2 5th and track work is your powerband.
I consider the S2 4-5 shift too large.
Certain powerbands will not like it and fall off.

Post you engine's curve, and we can give sound advice for the decision of turbo 5th, or S2 5th.

mortymower

That clears things up a ton odd job! thanks, so now more importantly how difficult is it to swap 5th gear's. Can a home mech do it or is that trans shop only

M758

If you guys have left over .829 5th gears 944 spec guys would be happy to buy them from you. It is the 5th ratio of choice for us.

I have been told all you need to do to swap 5th is pull off the rear cover. Having looked at the tech manuals on this it appears about right. As for it being a DIY job, well that depends on what level of DIY you are. I have never had the need to swap 5th so I have never done that, but would gladly give it a whirl if I needed to.

NEAL WRIGHT

I'll keep the S2 box in the car. Just went to WSIR and it was really impressive how the car came out of the relatively slow uphill turn 6 in 4th. Before, with the 951, I had to almost redline the car over the hill and quickly shift into 4th once the track straightened and flattened out. Not a good feeling because the car is at 22 lbs of boost at that point and felt like it could snap at anytime. Now, I shift at about 5200 -5500 into 4th and cruise right over the hill with the torquey 911's.

Another big (at least it felt like it) gain was exiting turn 9 onto the 3500 ft front straight. I am able to hold more revs in 4th through the apex. Holding the revs allows better response and feel. The biggest plus is to get into 5th about 20% down the straight rather than about 40% down with the turbo box.

Thanks again for the info!

mortymower

Where does one aquire a S2 or N/A 5th gear?

IPSC

Sunset Porsche can order them in from Germany. An S2 5th gear is under $80.00 but... the S2 R&P is $950.00 both are a 4 to 6 week wait.

IPSC


Running a stage 3 vitesse putting 300 to (hopefully) 350 to the wheels through a Turbo S trans (LSD and OIL Cooler) at the moment

Would a set up of; a S2 R&P along with a S2 5th gear "fall off?"

IPSC

333pg333

No I don't believe it will fall off at all, in fact as confirmed by those that have the S2cwp, you will be on boost more often. Tool may beg to differ, but I think if you use your car more on the road, you'll find there are more benefits than disadvantages. You may suffer a little in comparison to the turbo 5th, but on the hwy it does drone a little at cruise.
Of course as Thom mentions, maybe the 6 speed is the way to go. Apparently parts of it are larger than the 5 speed. Certainly of the aftermarket LSD's that we get made here, the one for the 968 box is much larger...next on list...maybe...

M758

Is that the same for a .829 ratio 5th? I heard dealer sourced quotes of $550 for the pair. If so that would be a steal. I bet sunsent could turn 10 gear sets in no time flat to 944 spec racers.

vette951s

According to a letter from the Weissach Racing Dept. at Porsche that came with the documentation I received with my Cup car, it lists the following changes made to the transmission in relation to the standard 944 Turbo: .."higher degree limited slip axle, strengthened differential & axle gears, strengthened transmission gears, close ratio 5th gear, steel synchronizer rings"..
Some of these changes were also incorporated into the Turbo S box, but for sure did not include the 5th gear or syncro rings. I don't know what the exact ratio is for 5th gear, but I can say there was a seat of the pants difference on the race track when I swapped in a spare Turbo S tranny. I know Porsches definition of "strengthened" is usually "hardness blasted" or shot peened for stress relief.

John

Oddjob

My guess is the $80 is just for the speed or the drive gear, not the full gear set. You need both the speed gear on the pinion shaft and the gear/selector hub for the input shaft. The gear hub assembly from the dealer includes the slider and is going to be the expensive half of the gear set.

For the S2 5th if someone wants to confirm:

016 311 159 AG speed/drive gear
016 311 353 AD selector/idler gear hub assembly


0.829 Turbo 5th:

016 311 159 T
016 311 353 K

Oddjob

John,

The close ratio 5th is off the "52 Differences" sheet, correct? That is the only place I have ever seen anything related to different gearing, and its only associated with the Rothmans/Canadian cars, not the Euro Cups or the US Escort Club Sports.

I would like to talk to you about that, but dont want to go off on a tangent unrelated to the S2 R/P topic here, so Im going to send you a PM (and I still need to reply to your strut bar inquiry).

Jim

vt951

Anyone have any idea what would be a fair price for an s2 r&p set with low miles in good condition? I found someone who has an extra set, and I was thinking of offering $400. Don't want to low ball, but also don't want to pay way too much. Thanks...

jyoon

i doubt there is any real performance gain on the street with street tires from changing r&p's and gearing it lower than stock. at any given speed, the stock gearing or the s2 gearing may or may not be better.

333pg333

Huh??
There is a total performance gain let me tell you. Especially if you have a fairly stock engine hp and capacity. The stock 5 speed gearing was designed more for high speed autobahn cruising and is great for that but not great around town. Changing the cwp to the S2 will give you a real advantage around town and on the track. If you do a lot of long distance hwy cruising then you might want to think about it.