mortymower

I have a 951 trans with a S2 ring and pinion installed by the previous owner. I like the first 4 gears but I want to install the S2 5th gear so I can reduce the Highway RPMS a little bit. I hear all you have to do for 5th is remove the back cover on the trans. How hard is this job, does the trans have to come out, and where do I actually purchase the S2 5th. Thanks

IPSC

An S2 5th gear can be had for under $100 from Sunset Porsche BUT... it takes 4 to 6 weeks from Germany.

IPSC

Oddjob

Yes, you need to drop the trans. 5th gear set is "behind" the rear alum cover, but it takes a little work to get it off. I recommend taking a peak at the trans section of the factory manual to get an idea of the scope of the project.

A lot of S2 track cars "mysteriously" end up with 0.829 Turbo 5th gears in them. Probably can make some calls around to some race/track prep shops and see if they have any leftover S2 .778 5th gear sets. Probably would be more than willing to do an even swap for the .829 5th.

New is an option, but $100 seems way too good to be true. Id be extremely skeptical that they did not quote the correct/complete items for the 5th get set.

016 311 159 AG Driven Gear
016 311 353 AD Idler Gear/Selection Hub Assembly (unfortunately this is only sold as the complete assy)

Cory M

The short 5th gear is in high demand for guys racing NA 944's. I recently swapped my tall 5th for a short one, I traded straight across for it. I dropped the trans to do it, dropping the trans took me longer than the swap itself. The part numbers of the seal and cap you need are in my post on the 944Spec forum: http://nasaforums.com/viewtopic.php?f=40&t=19223

You also need a gear puller, snap-ring pliers, a butane torch or hot plate is helpfull to expand the gear before sliding it onto the shaft, you will need new gear lube, an impact is helpfull for removing some of the bolts. I couldn't find the gasket locally so I used "Great Stuff" sealant and it worked fine, the cap is a must though.

If you posted a "Want to Trade" add over on the 944Spec forum you would have a line of people willing to trade you for their tall gear in no time.

M758

Do a swap with a 944 spec racer.

We want the 0.829 5th that you have and would gladly trade you the 0.729 5th gear pair.

Jeremy Himsel

Yup, I'll swap you the one out of my Sepc car trans.

mortymower

I don't have the factory manual and clarks has nothing, where can I find a procedure?

Oddjob

Sorry to chase off the N/A vultures....

Morty, you dont want the 944 N/A 0.729 5th, thats too tall. Stick with looking for the S2 .778 5th.

You will have a hard time finding any trans write-ups other than the factory manual.

333pg333

For the 951's with the S2 cwp, what would the transition be like having a taller 5th gear ratio? Obviously it is dependent on use and power band, but is it a realistic option or would you just go into wallow mode while it built up boost - speed eventually?
Sorry a bit of a convoluted question but I'm sure you get what I'm asking.

Oddjob

The S2 R/P is 15% shorter than the Turbo R/P.

So if you put the S2 R/P in a Turbo trans - the final drive will be 15% shorter in each gear than a stock Turbo trans.

The final drive in 5th gear with the S2 R/P and S2 0.778 5th is 7.5% shorter than the stock turbo transmission.

The fiinal drive in 5th w/ the S2 R/P and the N/A 0.730 5th is approx the same as a stock turbo trans. So you would be shifting from a 15% lower 4th gear to a basically stock 5th final drive ratio. That would be a big drop from redline in 4th, 2000 rpm down into 5th - would feel like hitting overdrive.

And thats why all the N/A guys cant get rid of the tall 5th fast enough - worthless on a track car. Maybe something you can deal with if you have a street only car and do a lot of freeway cruising ....

Cory M

The original posted said he wanted to reduce the highway rpms, the .729 944NA 5th would do that... I added a link to some pictures to my thread on the 944Spec board if you want to see what the trans looks like with the rear cover off.

Oddjob

The S2 is the .778, not the .730. Its all subjective, but I would argue that the 730 would be too much of a drop between 4th and 5th, and reduce rpms more than a little bit.

333pg333

Thanks Jim. I pretty much expected that answer but that's the compromise you have when it's a street/track car. I love the S2 cwp swap, but that top gear is a bit of a pain when on the hwy. Short of doing a 968 6 speed swap and then customize the gearset, I don't think there's a magic answer. The only possible thought I had was that with a lot more power and tq than stock with a larger capacity motor(say 3.0L +, 450hp/tq + ), you might be able to live with it as you can just push through with the extra horses?
could have a quicker

mortymower

I would like to reduce the RPMS as much as possible and whenever I want to accelerate on the highway I drop down to fourth or even third anyway and I rarely hit redline in fourth on the street so I dont think it would be a problem. That way I would have the first four gears really short to accelerate and the 5th to cruise. However, would the N/A 5th be strong enough for a 300-350 HP 951

Cory M

I think the taller 5th would handle the power just fine, it is a common swap for V8 conversions who want to reduce their freeway RPMs.