What Steel Intermediate Shaft Gear are People Using These Days?

[Evan Fullerton]

Still collecting parts for my build. With stiffer valve springs (Aasco) on some big valve heads (xtreme) and a GT3 oil pump i’m going to be loading the intermediate shaft gear a lot more then a stock 3.0L so I want to go with a steel intermediate shaft gear.

Straight cut options:
JB Racing - called them, out of stock not planning on making more.
Pauter - Rumor is they are LOUD and after seeing the finish work on the $$$ rockers I bought from them, not overly keen for such a critical part.

Factory options:
993 gears seem to be available. Different tooth count to the original aluminum gear I read so have to replace the crank gear also.~$900 currently I am seeing.

996 Turbo gear. I believe the same as the 993 gear but Porsche lists a different part number. Porsche seems to want less money for this one for some reason. Back when I worked at a Porsche shop we did have a 996 Turbo come in with a broken drive gear on the crank. Maybe a 1 off quality issue but slightly concerning. The revised tooth count doesn’t seem like it would be as strong but probably quieter?

GT3 - These use what was originally a 959 part but appears to be super seeded to a 000 number now? Looks to be the lightest strongest option as it is 1pc. with the intermediate shaft so no bolts to come loose which I guess happens occasionally on 996TT due to the harmonics…….. but they want $2500 these days for one from what I can see. It does however also use the original tooth counts. Seems like a winner but the price is a bit steep. Found a 997 number for it also from a Cup catalog but I don’t think PMNA is likely to sell it to me though I suspect it’s cheaper then the street car part number?

I don’t have access to PET so I can only rely on Google but anyone have experience with any of these different options as a retrofit into an early engine recently and have a good part number for one to fit a 0 case?

[JackkTheMackk]

I was in your exact shoes a year and a half ago with my 3.2SS. gt3 pump, JBR springs/steel retainers (so would not use Ti retainers in a street car), extreme heads, dc60 cams, etc etc. I was lucky enough to score some JBR straight cut gears. The whine is not that loud and I don’t mind it.

You might have trouble finding JBR straight cut gears so the second best alternative would be paying for a new set of matching 993 gears. You will need both the bottom and top gears. I saw photos of failed pauter gears and would not put them an in engine.

Don’t forget to change out both cam gears on the IS shaft for new gears while you’re in there.

[stanglife]

Can I piggy back on here?

Building 964 and considered changing the gears - case is 0. Is changing from aluminum something that is common on hot-rod motors? Also have built heads/springs/cams.. Is there a popular path for this on 964 builds?
Thx!

[Evan Fullerton]

Stanglife,

Based on my research, only ‘89 964 would have had the Aluminum gear. Is yours a super early build?

I don’t know what prompted Porsche to switch to steel in 1990, I suspect it was durability with the added power steering pump load or possibly also noise with why they changed the tooth counts?

All the racing cars seems to run straight cut steel gears for durability back into the 70’s. 959 used a helical cut steel gear that was very similar looking to the 962 setup but helical cut with the older later tooth profile of the aluminum gears.

I have to assume driving 4 cams and cam driven water pumps added a lot of load.

[gled49]

Use the 993 intermediate shaft and crank gear, it will hold up and run quite.

[gled49]

Pictures

[blue911rsr]

What was the failure on the Pauter gear

[Evan Fullerton]

Pulled the trigger and ordered 996 105 911 70 we will see what shows up.

The 996 Turbo crank gear can be bought separately and has a 901 part number so that has me thinking Porsche went back to the earlier bigger tooth profile after the 993 for both the turbo and the GT3. Has to be a reason right…… and it’s cheaper.

[svcetiquette]

I've tried to figure out what steel gearset this is in my current race engine. It only has "2705" engraved in it, and "Made in Germany". No 0 or 1. I've searched for the source, but haven't had any luck. Maybe someone recognizes these from another aftermarket source.

[Evan Fullerton]

Looks like a factory gear to me.

If you count the teeth and compare to the aluminum one, if it’s the same, I would say 996 Turbo…. If the number is different, 964/993.

The same 4 digit number marked on the gear should also be on the corresponding crank gear to be a matched set.

From what I could find the intermediate shaft gear either 993 or 996 only comes with the crank gear as a matched set.

[stanglife]

Originally Posted by Evan Fullerton

Stanglife,

Based on my research, only ‘89 964 would have had the Aluminum gear. Is yours a super early build?

I don’t know what prompted Porsche to switch to steel in 1990, I suspect it was durability with the added power steering pump load or possibly also noise with why they changed the tooth counts?

All the racing cars seems to run straight cut steel gears for durability back into the 70’s. 959 used a helical cut steel gear that was very similar looking to the 962 setup but helical cut with the older later tooth profile of the aluminum gears.

I have to assume driving 4 cams and cam driven water pumps added a lot of load.

It's a 90 crank so it's likely not aluminum. This is just me learning more and more - thank you for the information there!

The engine it came from had unknown miles but crank is standard. So many other new parts in the engine, I am curious if replacing these gears would be of any benefit. Here are some pics..at the time I was taking pictures of the chain gears but the IS is in there too.

[stanglife]

[Old H2S]

I'll go first..That looks new.

[stownsen914]

I see chain marks on the sprockets, but appear to be in good condition. No pitting evident on the larger gear.

[stownsen914]

Been contemplating the same for my 3.5L race engine. An aluminum gear was in it, and turns out is probably the reason I tore the engine down - metal flakes in the oil filter. The aluminum gear shows substantial pitting.

@Evan Fullerton 996 105 911 70 seems to bring up an intermediate shaft assembly, which may include the crank gear? Is that what you purchased?

[Evan Fullerton]

Long story short, I ordered from Porsche 996 105 911 70 and supposedly a new in box 993 105 911 56 off eBay.

We will see if there is any differences between them, both are supposed to arrive in a week or so and I’ll post my findings. Assuming they are the same or similar, if anyone needs a set for a 0 case…… I’m going to need to offload one of them.

[stownsen914]

Gotcha, may be interested

[Evan Fullerton]

Well here is the 993 part number option. Gears are both laser marked with matching numbers and both have a 0. Comes with the shaft.

[Evan Fullerton]

Here is the 996 Turbo gear. Looks VERY similar but the big gear/shaft isn’t as shiny. Looks like it was acid etched or something after manufacture.

[JackkTheMackk]

Mind weighing the both of them? Curious if they’re different weights.