Where to get 47mm CV bolts?

[cay-ahe]

I've searched and researched CV bolts. When I buy a new CV/Axle assembly it comes with 47mm bolts. Now I want to replace these bolts before the heads strip and cause me headaches. As far as I can tell I can buy 50mm or 45mm bolts for my application. So do I get the 50mm and put a couple washers on there to shorten them? 48mm would be ok I think. Thoughts or source for 47mm bolts anyone?

[Grady Clay]

Keith,

The bolts from industrial suppliers typically come in 5 mm increments (45, 50 mm) in these lengths. When you see intermediate lengths (47 mm), they are typically Porsche part number pieces or ‘specials’ for an OEM supplier.

Using longer bolts is best accomplished by having them machined shorter. Do NOT use washers as spacers – these are already tenuous as to holding the CV joint in place. When shortening, be sure to have the ‘lead-in’ feature on the first thread or so.

The general spec for bolt through the flange is 1½ threads. Always check the back-clearance between the end of the bolt and the transmission casting when pushing the CV joint and flange toward the differential.

Please read this thread:
Reconstructing Constant Velocity (CV) Joints
While very long, it is the best word on CV joint attachment.
It is worth studying in detail.

I would go to the effort to convert a track 911 with the small 100 mm (type 923, 912E) CV joints to the larger 108 mm (928, 930 Turbo and 911 after about ’85) 6-bolt, M10, end-cap CV joints. This gives longer life and greatly reduces the possibility of a CV joint coming loose while on track.

Best,
Grady

[gtc]

My mechanic bought mine through WorldPac, I'm pretty sure.
Alternatively, if you can find and use a set of "moon plates" as well as schnoor (belleville) washers, they would probably take up your extra 3mm if using 50mm bolts.

[T77911S]

+1 for grady.

you can get the bolts at fastenal, but they will be 45,50,55 or so. but you want some threads sticking out the other side of the flange. mine were short and when one came off, i "upgraded" to a longer more correct length. they also sell the washers too. a bag of 50 is not that much.

[Grady Clay]

Originally Posted by gtc

Alternatively, if you can find and use a set of "moon plates" as well as schnoor (belleville) washers, they would probably take up your extra 3mm if using 50mm bolts.

Yes, probably an acceptable solution. Be sure the surfaces are clean and the plates are flat. I would not use more than two plus the Schnorr washer. Best is the correct length.

Best,
Grady

[RWebb]

bolts MUST meet the Porsche strength spec.

[cay-ahe]

Thanks for all the input.

Grady - I did read the thread you referenced it just wasn't clear to me what to do with my 47mm bolts. When you say convert "to the larger 108 mm (928, 930 Turbo and 911 after about ’85) 6-bolt, M10, end-cap CV joints" are you saying get different part # for the trans-axle flange and stub axle. What would be involved in the conversion? This sounds like the best way to go, although I've never had any issues.

[Grady Clay]

Keith,

Yes, the best solution is to update to the larger CV joints.

This takes a pair of:
108 mm, 6-bolt, M10 transmission axle flanges.
928S axle assemblies (standard ’85-> 911).
108 mm, 6-bolt, M10 stub axles.
and hardware.

Does someone have the part numbers, applications and descriptions?

The issue is finding the transmission axle flanges that fit your differential gears (course 18 spline) as the 915 flange starting in about ’85 is fine 43 spline.

Best,
Grady

[T77911S]

Originally Posted by RWebb

bolts MUST meet the Porsche strength spec.

yes, fastenal's are 8.8.

i just checked, a bag of 50 is 19.25 for the bolts.

[cay-ahe]

Great info. If anyone has part numbers or model numbers for these parts that would be great. M10 stub axle from a 19xx 9xx? So the splines inside my current hubs are ok?

[Grady Clay]

Originally Posted by T77911S

yes, fastenal's are 8.8.

i just checked, a bag of 50 is 19.25 for the bolts.

NO
Do NOT use 8.8

The CV joint bolts are 12K or 12.9 DIN/ISO specification.

Torque specification is:
M8 bolts (6 mm internal hex) - 33 ft-lbs (42 Nm).
M10 bolts (8 mm internal hex) - 60 ft-lbs (80 Nm).

Best,
Grady

[orcadigital]

As I understand it, Metric 8.8 = SAE Grade 5. Could be wrong.

But anyway, same as what WorldPac sells, Part #ATM893407237 available from NAPA. It is 8mm x 48mm which I "think" is what you are looking for? It fits 914's with 901's, and as I understand it was the same for 915's. I used them on my 914 before I sold it. They are the OE 12-Point as well.

Store Locator | NAPA Online

Hi Grady! *waves*

Grant

[RWebb]

just use chewing gum - no need for bolts

[gtc]

Originally Posted by T77911S

yes, fastenal's are 8.8.

i just checked, a bag of 50 is 19.25 for the bolts.

That is not exactly true, they also sell 12.9.

[Jdub]

Keith:

I am taking Grady's advice and plan on assembling the parts for this upgrade. For now, I will repair what is damaged to get the car on the road (for me, a helicoiled flange and fresh seal, plus new bolts/Schnorrs).

The trick for us with our SCs will be to find the coarse splined flanges in the 108 configuration. After that, I believe it is all downhill.

John

[cay-ahe]

Originally Posted by orcadigital

As I understand it, Metric 8.8 = SAE Grade 5. Could be wrong.

But anyway, same as what WorldPac sells, Part #ATM893407237 available from NAPA. It is 8mm x 48mm which I "think" is what you are looking for? It fits 914's with 901's, and as I understand it was the same for 915's. I used them on my 914 before I sold it. They are the OE 12-Point as well.

Store Locator | NAPA Online

Hi Grady! *waves*

Grant

I tried to verify it is 48mm and kept coming up with 45mm?

I did however find a Jetta CV bolt that is 8 x 48mm on this site part #893-407-237-M6036. I am hoping this would have the correct strength and threads. What do you think?

[cay-ahe]

Originally Posted by Jdub

Keith:

I am taking Grady's advice and plan on assembling the parts for this upgrade. For now, I will repair what is damaged to get the car on the road (for me, a helicoiled flange and fresh seal, plus new bolts/Schnorrs).

The trick for us with our SCs will be to find the coarse splined flanges in the 108 configuration. After that, I believe it is all downhill.

John

If you are able to come up with a parts list please let us know. I'll do some research as well. This may be a entrepreneurial moment. Coarse spline flange CV adaptation kits. We could be zillionaires.

[orcadigital]

Honestly I do not know Keith. I sold my 914 and the spare bolts i had. They did match the originals that came out of several cars though. Not knowing the original length of the 914 bolts though, I am just not sure.

As far as strength, they are provided to NAPA through their Altrom line, which is based in Canada, but specifically works with OEM suppliers for imports. The 893407237 is the original bolt on several Audi's and VW's. I never had any issues with them, and my 914 was a track car. It was also a stock 4 cylinder, so I wasn't exactly stressing them with oodles of horsepower either... Oddly, the NAPA catalog only lists them for 914's, but to be fair their catalog integration with Altrom, especially for Porsche, is an ongoing project.

If 901 and 915 CV bolts are the same, then I'd say they will work fine.

[Eagledriver]

I think that the 76-84 tranny's used fine spline flanges. The turbo/ 86 Carrera flanges are fine splined. This is why they make a great upgrade for SC trannys. Unfortunately this is also why they cost an arm and a leg. I have an early car (72), and I use the original flanges (108mm with course splines). These early course splined flanges will work with the 86 Carrera drive shafts by drilling and taping the 2 blind holes where the dowl pins used to go. The steel grease cap has a slight interference with the depression in the flange face but it seems to not be an issue. The grease cap just forms itself to fit as you tighten the CV bolts. Make sure you know whether you need course or fine spline flanges before you spend your money.

-Andy

[T77911S]

Originally Posted by gtc

That is not exactly true, they also sell 12.9.

i only priced the 8.8,

i thought that was what was on the bolts i took off when i replaced my CV boot.
i was concerned about the hardening so i went with what was on the bolts that came off the car.

my point is, they sell the bolts you need and in various lengths. plus they let me take a few home to get the right length. i now have a few threads sticking out the flange side as opposed to the botls being too short, but now i need to check the grade. i still have the ones i took out so i will dig them up and check them.