83 3.0L Engine & Trans Swap to 85 3.2L Engine & Trans - Axle Options

[Gordo2]

Folks,

I have an 83 SC with stock trans & axles (type that has open/detachable CV's with 6 bolt flanges that attach to the trans and outer wheel hub -100mm?).

I bought an 85 Carrera and want to swap the engine and trans into my 83. The Carrera has the newer, sealed CV joints (108mm attaches to wheel hub with the axle nut as opposed to individual bolts through the CV).

Should I take the flanges off my 83 trans and mount to the 85 trans and use the original older style axles/CV's or swap the wheel hubs with the ones off the Carrera and go with the newer style axles/CV's?

I searched and didn't find any help, appreciate your input.

Thanks, Gordo

[Peter Zimmermann]

What is your ('85) 915/xx number?

[Gordo2]

The 85 shows 915/73 74F 03393

Thanks, Gordo

[Flat6pac]

The trans hubs are interchangable to both transmissions, so what ever is easiest...
Bruce

[Peter Zimmermann]

Originally Posted by Flat6pac

The trans hubs are interchangable to both transmissions, so what ever is easiest...
Bruce

That should be correct. Porsche assigned a lot of different part numbers to the axle flanges for '83-86 models, and I've never seen an explanation as to why. That said, I've never seen a 100mm flange not fit into another '80> 915, even those fitted with LSD ('79 and earlier had coarse splines).

[Flat6pac]

78/79 are fine spline also
Bruce

[Peter Zimmermann]

Originally Posted by Gordo2

The 85 shows 915/73 74F 03393

Thanks, Gordo

That's the correct number (/73) for an '85 915, and that trans should be fitted with 108mm flanges. You can remove those flanges and replace them with your SC flanges (the axle flange seals are the same).

[Gordo2]

So to sum up,

1. The transmission flanges between the 85 and 83 trans that I have are interchangeable. Differences in flange size.

2. The hubs are the same? I should be able to insert the axle stubs from the 85 into my 83 hubs?

Based on above, I'm confident in # 1, not so sure on # 2.

Thanks again folks,

Gordo

[Flat6pac]

#2, the splines and length are the same

[uwanna]

Using the later axles would be a very good idea. With the larger CV joints and larger axle you'll a much more robust setup. All Turbos since the beginning have used the larger axles and CVs. One point of strength is the use of
10mm CV bolts instead of the kind of puny 8mm ones!

[KTL]

Originally Posted by uwanna

Using the later axles would be a very good idea. With the larger CV joints and larger axle you'll a much more robust setup. All Turbos since the beginning have used the larger axles and CVs. One point of strength is the use of
10mm CV bolts instead of the kind of puny 8mm ones!

I agree wholeheartedly. There's many instances on this forum of people dropping axles on account of the smaller CVs and smaller 8mm bolts. It's much less common to hear of people with the 10mm bolts and 108mm CVs having axles come loose. This is one of the upgrades i'd like to do to my racecar.

[Peter Zimmermann]

Originally Posted by Flat6pac

78/79 are fine spline also
Bruce

Uh, no. Here's the story. 915/61 model 915s, built through the 1979 model year, use coarse spline flanges that carry part number 923 332 209 02.




Beginning with 1980 SCs, the switch was made to stronger, fine spline flanges, part number 915 332 209 12. These flanges were also used on 1984, non-Turbo Look, 915s. 1980-83 models were type 915/63 (USA), and '84 Carrera models were 915/68 (USA). 915/62 (RoW '80-83) and 915/67 (RoW '84) used the same flanges as the USA models.




This is the difference between the two flanges...




And...



Even the bolts are different. 915/61 transmissions use a "stretch" bolt with flat washer, while 915/63/68 models use a "hex" bolt with no washer. Stretch bolts require a 19mm socket, hex bolts require a 17mm socket, and the torque for the two fasteners is different.



Then the game changed in 1985, when the 915/72(RoW)/73(USA) were fitted with 108mm flanges/CV joints, identified by the use of seal caps/covers on the inboard CV, instead of previously used gaskets, and 10mm bolts. This enabled Porsche to use the same 915s/flanges/axles in all regular and M491 Carreras.

[KTL]

Very nice summary Pete. Feel free to send me some of those 108mm flanges w/10mm bolts if you have some just sitting around collecting dust.............

[Gordo2]

Pete,

I've been searching threads on this stuff for the past 3 nights and didn't find anything as conclusive as what you just posted - you just dumped the masterload!

Much appreciated, great stuff.

Thanks again. Gordo

[Flat6pac]

The 923 part number is for a sportomatic trans.
Im not trying to be difficult but 30 years of knowledge bites the dust if im wrong
Bruce

[uwanna]

Gordo,
The flanges in the pic below are are the two types of 108mm w/10mm bolts and the 100nn w/8mm bolts. The ones on the left are the early Turbo flanges, the middle are what you have on your '85 915, and the ones on the right are the ones on your SC. The middle ones have become very sought after and are rare as "hens teeth" because they were only used from '85 1/2 thru '86. If you decide not to use them, they will bring $400-500 in a heartbeat on the for sale forum!!
However, I'd still suggest that you use the larger''85 axles w/much larger CVs on your engine swap! One other plus on the larger axles is, they have a "cap" on the inner CV and don't need a gasket. Much cleaner and no greasy hands when removing inner axle from the flange!

[Flieger]

Originally Posted by Flat6pac

The 923 part number is for a sportomatic trans.
Im not trying to be difficult but 30 years of knowledge bites the dust if im wrong
Bruce

I thought 923 was the 912E type number. The sportomatics were 905 for the 901 and 925 for the 915 version.

[Gordo2]

Originally Posted by uwanna

Gordo,
One other plus on the larger axles is, they have a "cap" on the inner CV and don't need a gasket. Much cleaner and no greasy hands when removing inner axle from the flange!

Having recently removed, cleaned, inspected and re-packed the CV's on my '83 - I definetly recognize this as a tangible benefit...

Gordo

[Peter Zimmermann]

Originally Posted by Flat6pac

The 923 part number is for a sportomatic trans.
Im not trying to be difficult but 30 years of knowledge bites the dust if im wrong
Bruce

Early Sportos, through sometime in '74/75, used part number 901 332 209 15, or 209 21, depending on which housing was used.

Beginning sometime in '74 part number 915 332 209 01 covered 911/911S/Carrera 2.7 models, but NOT Sporto.

Beginning in '75 (probably with the intro of the 912E), a switch was made to #923 332 209 02, used on 912E/911S/Carrera 2.7, but NOT Sporto (this was when the switch to 100mm flanges occurred).

Then, probably when the switch was made to the 3-speed Sporto, flange # 925 332 209 05 was introduced for the last series of Sportos built.

[Gordo2]

Thanks for the info guys - smooth as silk.

I removed the axles, and transmission & wheel hub flanges from the '85 and installed on the '83. I would like to say "no sweat" but it was about 95 degrees this weekend.

Gordo