half shaft angle to the transaxle??


In a set up with a Porsche transaxle, what kind of angle should I expect to see for the half shaft to the axis of the transaxle looking down from above the car?

How close to 90 degrees should I expect? How much deviation is allowable?

We loaded the engine into the car today. The outside of the half shaft is somewhat forward of the inside ... so the angle that the half shaft makes with the centerline of the transaxle is less than 90 degrees. Looking to understand how bad off I am.


Tim Kay

Lifetime Supporter

I am watching your post with interest because you and I are close to the same phase /ubbthreads/images/graemlins/wink.gif

I installed trans and motor mounts in the last 2 weeks (G50/52). My half shafts are roughly 2-3 degrees forward and 20 degrees high at the trans flange center-line. Of course I say roughly because the cv's and axles aren't in yet and I am 'eyeballing' and using a straight edge to get approximate angle.

I am not too concerned about the angle being any problem. CV's should not be 'straight on'. They are designed to have some inclination to them at all times. Now depending on the size of CV, that will determine to what maximum degree you can go but with our cars we will never approach the maximum inclination in our suspensions (could be wrong but I believe it's 28 deg max with 930 cvs)

In our case, the angle already achieved in the vertical direction automatically takes care of any minimum inclination (we have more than enough there) so whether your 'straight' on with the for\aft position doesn't matter one way or the other. (hope I didn't confuse you /ubbthreads/images/graemlins/crazy.gif)

Chris Kouba

Just to clarify, the cv doesn't care if it's vertical or horizontal displacement, right? I would assume the only concern is the total angular articulation regardless of which direction its components go.

Just a question...

OK Guys,

Am not using CVs ... can't afford them. Am using Spicer 1350 u-joints on heavy flanges and slip tubes. Difference in cost of the approaches is over $1000.

Looking down on the car, the angle as assembled measures between 2 1/2 and 3 degrees with the wheel end of the half shaft being forward of the transaxle output plate center.

The chassis was originally configured for a G50. Am using a G50/52 that appears to be slightly longer.

Which is better ... leave it as is, or move the upright back closer to a 90 degree angle and cause the shock to move to a less than 90 degree angle when viewed from the side of the chassis?

If I move the upright back 1/2", the shock will have a 2.5 degree slant from the rear upward to the shock mount when the shock is fully extended and unloaded. This angle could be as great as 3.5-4 degrees when the shock is loaded and compressed.

The structure of a shock doesn't seem as if it ought to be as forgiving of angles in that direction as the double u-joints and slip yoke.

Tim Kay

Lifetime Supporter

Can't offer much here regarding 'u-joint' knowledge but my first concern is that moving the rear upright wherein changing the geometry of the shock may create a problem on the lower a-arm in terms of load (not to mention maintaining correct geometry thoughout). I would tend not to change the shock angle and go with the angles on the half shaft. My .02 /ubbthreads/images/graemlins/crazy.gif
"the angle as assembled measures between 2 1/2 and 3 degrees"

Agree with Frank, about 12 deg. max, 2.5 to 3 is well within that.

You may want to take the spring off the shock and go through full suspension travel and look at the total driveshaft angle. It's probably greatest at full droop. The front to rear offset will add to the total but not by much.

A max total angle is probably called out by the manufacture.

You could probably even disconnect one end of the shock and let the suspension full droop until it hits/binds then spin the wheel and check for axle joint bind just as a confirmation.

Agree with Tim also, suspension geometry is more critical than a 3 degree offset axle.

Tim Kay

Lifetime Supporter
My half shafts are roughly 2-3 degrees forward and 20 degrees high at the trans flange center-line.

[/ QUOTE ]
Update, took a closer look and the vertical angle on my short shafts are more like 15 deg full droop, more likely about 12 deg static like mentioned by Kalun and Frank.

I quess the main thing is ideally with cv's you want some but minimal degree of articulation, there is a bit a latitude though. With u-joint half shafts vs cv half shafts it may be a bit more sensitive, I would like to know /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/smirk.gif

Check with Bill Bayard. He's running same axles/tranny.
My recollection is that his shafts have signicant "misalignment"
but it sure doesn't seem to be a problem. Most DRB's
have the same setup and they seem to be very durable.


Lynn Larsen

Lynn Larsen

When I was doing my research to make sure my U-joints were in phase, I repeatedly saw 3º as the max on U-joints. Keeping in mind that this has some built in over engineering, I'd say you are OK.


Tim Kay

Lifetime Supporter

1) CV's are stronger (u-joints may be equal but not stronger - they both break /ubbthreads/images/graemlins/mad.gif)
2) CV's more readily available in the event of r&r
3) Less maintenance
4) Safer - in the event of failure the axle will remain inside the CV housing and a u-joint failure can cause the axle to become a 'demolition ball' and destroy whatever is around it.
5) Cost for u-joints, by the time you fabricate stub axle flange adapters, trans output flange adapters, yokes and axle slide yoke you may be comparable to cv's /ubbthreads/images/graemlins/confused.gif
6) In a GT40 application - extreme angle inclination won't come into play, CV's will allow for that. (in off-road cars CV's are most common due to long suspension travel in addition to strength)
7) As in the above topic, alignment may or may not be a bit more critical with u-joints.

My half shafts cost $ 650 pair (not including the trans adapters) and Bill Bayard hasn't broken one yet.
They look stronger than any CV's I can get for that level
of cost.

But if I had an unlimited budget, I'd go for CV's
since they are the more modern design....less space...
less vibation....can handle more mis-alignment.
Of course most kits already come set up one way or the
other....and changing over isn't cheap.


I just saw the picture of your car on another thread. I may be asking a stupid question but, why can't you leave your motor mount height about where it is but drop the rear of the trans? From what I see, this would give the motor a tilt as in a front engine application, give your distributor some distance from the fire wall, flatten your half-shafts and lower your center of gravity. I am looking at doing this type of install on my GTD this winter and it seemed possible?!
P.S. AWESOME Exhaust!!!


The engine is not quite level ... slanting slightly down to the rear. There is 1" clearance under the transaxle at the rear of the frame for a mount. Can bring it down a little, but not much.

The half shafts cost $521 ... and they are a bit sturdier than Bill Bayard's.

The adapters are being made out of 17-4PH stainless steel. The material was $45 on eBay. The adapter to transaxle bolts are grade 12.8 (6 10mm-1.5 pitch on a circle of 3.695") and the half shaft to adapter bolts are grade 8 7/16-20s (4 on a circle of 3.75" but NOT evenly spaced!).

I think the 2.5 to 3 degree forward rake of the half shafts will be OK. The distance between the engine/transaxle adapter plate to the centerline of the transaxle output pinion is 8.440" compared to Bayard's G50 at 8.308" Short of relocating the engine forward ... which really would put the distributor in the soup ... there's no fixing it without relocating the lower mount for the shock.

The distributor problem has been fixed by rerouting the front plug wire back through the cap. Gives me 1/2" clearance in the front of the cap with no obstruction over it.

I do have to modify the valve cover to get rid of the high standing breather. I have a breather tank for it, but will have to work on the cover.

Assuming I can make the adapters (which are ~$450+ship from GT40 Australia), I think things are pretty much OK. I did screw up the second bolt circle on the first adapter blank and am remaking it. I was able to do the proper location of the holes by transfer punch on the test blank but it really does need to be replaced.

The rear transaxle mount is next, then the fluid circuits.

Thanks VERY much for all of your comments. They really did help me work through the thing!