5th. Gear swap in Turbo Transmission.

I have just obtained a Turbo Transmission with a LSD. Is it necessary to change the 5th gear for general road use with a LS1 in my 944?
Car will not be used on the track, road use only.

Not that I am aware of, it just allows for better highway cruising and top speed.

Necessary, no.
Highly recommended...yes!

On the other hand it's pretty easy to pull the trans out on these cars, so if you waited until later to do it i don't think it would be that much extra work.

Does it drop the cruise RPM by much?

I did the 5th gear swap. Does it help, yes, how much, not as much as you would think. There is a spreadsheet calculator on R---list that calculates the impact you should see based on rpm, tire size..., I may have a higher top end by maybe 10, but the rpm for 60 is around 2100 and 70 2500 in 5th.

I did the NA 5th gear swap and put larger tires on the back (currently running 285/35/18's) and my cruise is 2500rpms @ 75. With stock-size tires and the turbo 5th i was @ 3,000 rpms before.

There's a big NVH difference between 2500 and 3000, even though it's not a big RPM gap. The bigger tires also make all the other gears longer, i recommend them as well.

Thanks for your input guys.

Hey Posche, do the 285's fit with no fender mods? What year is yours again, late model?
Thanks,

The 285's fit with no fender mods. I've heard up to a 305 will fit with no mods, but i wanted a taller tire (285/35 is taller than the 295/30 that came on my rims) and tire sizes are pretty limited.

I have an '87 with 18x11 rims. In order to get my Turbo Twist II's (hollow spoke) to fit i had to switch to an '86 rear hub, but if you get the right offset you'll have no problem fitting 285+ tires.

Why did Wheel Enhancement tell me that they couldn't offer me anything off of another Porsche wider than 9.5"? You have some 11"? I was thinking CCW was one of the only options for wheels that wide, either that or conversion plates for wheels of a vette. The wide bolt pattern makes finding wheels for these cars kinda a challenge.

Wheel Enhancement ?...



Check out some of the eBay stores.
And LugmanUSA.

Adapters and spacers broaden the search considerably.

har har

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Whether or not I eventually bought the wheels from them it seemed like they would be able to tell me all of the available Porsche wheels, then I would only have to use a spacer and not an adapter. Apparently they blatantly gave me the wrong information, because I'm looking through their website posts and there are obviously wheels wider than 9.5" Maybe the guy I got on the phone just didn't know what he was talking about, and I didn't have access to the web when I called so I just took his word for it.

I don't, however, see anything that wide which is smaller than 18" in dia. I was hoping to go with 17", just to keep weight down and a little bit more sidewall for uneven pavement. I'm not convinced that the super low profile needed to keep the overall diameter in spec while using 18's or 19's is necessarily advantageous. Unless I use an adapter I might be out of luck for 17's (unless I spend an arm and a leg for CCW's)

To be honest i don't think i've seen any 17x11's, so maybe that's what the guy was talking about. There are some decently light wheels in 18" though...just don't get them through wheel enhancement, unless they're GENUINE porsche! I picked up some of those 18" techno wheels because i loved the style--they were 34lbs each!!!

Now i have genuine 996 Turbo Twist II's (the second one on their website). I paid $600/set for genuine Porsche hollow spokes and they're 22/24lbs front/rear, respectively. They're a funny offset so they're cheap, but to fit them on an '87 you have to use a 7mm spacer on the front, and swap to an '86 Turbo rear spindle on the rear + 15mm spacer. It's a lot of work but i love the wheels and the price was right.

Yeah, that sounds right. There don't seem to be many 17x11's anywhere (Porsche or not). Correct me if I'm wrong, but I think ZR1 wheels are 17x11's. Don't really like the way they look though. The other problem are tires, kumho makes a 295/35R17 which would be perfect on the back with an 11" wide wheel. They would be .2" larger in overall diameter than stock. Finding a good tire size for the front is tricky. I was thinking a 265/35/R17 or a 275/35/R17 (.6 under and .3 under respectively for overall diameter) would be perfect for the front but I can't find anyone who makes that size yet. I did find some at 255/40/R17 (.1 over) that would be perfect diameter wise but I'm worried that there would be too big of a width difference between front and back if I went with 255's up front 295 rear. I might just have to go with 18's.

I just realized I totally hijacked this thread, sorry. I'll shut up now.

When i swapped the 5th gear in my Turbo LSD transmisiion I stupidly installed a later NA 5th gear. Excuse is I never cross checked the NA box code with the gear charts.
Now I have obtained a 0.73 gearset and really do not want to drop the transmission again.

Has anyone modified the spare wheel well to allow sufficiant clearance to remove the transmission end cover? How much metal has to be removed?

I am currently attempting to do the spare tire well chop for a few reasons and the ease of trans dropping is one. I am think once I drop it I could easily use fiber glass to cover the hole. But its builders choice really.

As far as how much is needed it really is quite a guess for me, I figured I would cut out to the first flat section in the well above the curved wheel well. Some where right below the German markings. Depends on if you have plans for the well or not. If you do not plan on using it at all you can cut it out completely. I myself am going to put my fuse box and battery.

Thanks Colin,
Please keep us informed how it works out. Can you supply pictures when you cut metal.
Thanks Mike

It might be a little while for me to get the project caught up, in the middle of catching up on bills after my motorcycle wreck last year. But I will definitely post pics.

Colin,
Did you cut metal to do your 5th gear swap? I am about to do mine for the second time, the 5th gear from my original NA transmission was a a European ratio. I have obtained the correct ratio but really don't want to mess with dropping the trans. Any help welcome.

I haven't cut the spare tire wheel for the swap, since I had the tranny out. But I do intend to cut it out since it is useless to me with the big brakes and custom wheels. Anybody do that? I'd think you could do the 5th gear swap with that out f the way, but it's not hard to drop the tranny.

fliermike45 wrote:the 5th gear from my original NA transmission was a a European ratio.

What ratio did you get?

Sorry, I meant my transmission was a 1988 ROW (Rest of the World) spec.
Code was 5Y, 5th gear ratio was .83