late 901 trans into SWB car help

[ty901]

I went through something similar about 2 years ago with my '66. this go round has a twist.
the car is a '68 w/ 90mm CV joints & axles. it came to the current owner w/ a 4-speed trans.
I supplied two core 5-speed transaxles which the owner sent out to be rebuilt. (ie; use the best of both and build one)
one is a 901/13 type MAG case. the other is a 914/01 ALU case. the owner did not specify to his builder that the rebuilt unit was going into a SWB car. both supplied candidates have the later 100mm output flanges. the flange mismatch was discovered attempting to install the rebuilt trans and the axles. I guessed (hoped) that the 90mm flanges from the 4-speed could be installed on the rebuilt trans and all would be happy.
not so.
input appreciated.

[djpateman]

The 914/01 is not an ALU case, and the breather hole is in the wrong location; it is for a 914 application only. Generally the 914 boxes have a larger differential than the 901/902 boxes, and similar to the early 915 boxes. I might be interested in it.

[Matt Monson]

Originally Posted by djpateman

The 914/01 is not an ALU case, and the breather hole is in the wrong location; it is for a 914 application only. Generally the 914 boxes have a larger differential than the 901/902 boxes, and similar to the early 915 boxes. I might be interested in it.

His 901/13 box is the same way, with the bigger bearing on the differential.

The only way I see to making this work is changing out the axles.

[jpnovak]

The 68 is slightly unique in its output flanges, half shafts and matching stub axles. The output flanges are smaller diameter and have a different length than the later ones. The differential uses smaller bearings and overall width. There is a post somewhere in the archives that details some expensive machining required to match the later output flanges to the early transmission.

As Matt mentions, the only way I know to make this work is to swap out the stub axles and half shafts to match the transmission you are going to use.

Or, the other option is to find a 68 transmission and rebuild it. Not the easiest to find one these days.

[ty901]

thanks guys. Naive question: would it be possible to mix and match CV's ? eg: 100mm output from the trans to 90mm @ the stub axle ?

[jpnovak]

The internal spline diameter/count is often different. Then there is possibility of an axle length issue.

I have never tried to build one.

Wonder if a 924/944 joints/axles could work.

I ran into similar issues on my old car between 915 100mm-6 bolt flanges and 108mm/4bolt_2pin axles. I ended up swapping the stub axles in the trailing arms. That was the easiest option.

[ty901]

if we go the route of swapping out the stub axles, will any LWB era stub axle work ?

[ty901]

Originally Posted by jpnovak

The internal spline diameter/count is often different. Then there is possibility of an axle length issue.

spline count and axle length are different.

[ty901]

Originally Posted by jpnovak

I ran into similar issues on my old car between 915 100mm-6 bolt flanges and 108mm/4bolt_2pin axles. I ended up swapping the stub axles in the trailing arms. That was the easiest option.

when you say "old" are we talkin' SWB old ?
we're thinking that this could open a can of worms.

[ty901]

Originally Posted by Matt Monson

His 901/13 box is the same way, with the bigger bearing on the differential.

The only way I see to making this work is changing out the axles.

what we're seeing is MAG case 901 / 902 / 914 (mid-'69 forward ?) have a 35mm ID carrier brg. vs. the earlier units which have a 34mm brg.
we're thinking about sourcing an earlier carrier and having that swapped in.

comments please.

[gled49]

ALU trans carrier (diff) will not fit in a Mag trans. I think u have to make peanut butter/marshmallow conversion to your axles. SWB trailing arm stub axles are complete different from LWB. No diff parts are exchangeable between SWB Alu & LWB Mag, except the R&P gears. G

[ty901]

thanks Gordon.
the plot thickens.
I never liked the idea of stub axle swapping so it's nice to know it can't be done
another idea rattling around my pea brain is this... it seems to me that the LWB axles are at least a couple of inches longer than SWB.
what about cutting the LWB axles to length and then cutting splines to match a SWB CV joint on those ends ?
could this be done ? am I crazy ?
answer the second question first

[Matt Monson]

Originally Posted by ty901

thanks Gordon.
the plot thickens.
I never liked the idea of stub axle swapping so it's nice to know it can't be done
another idea rattling around my pea brain is this... it seems to me that the LWB axles are at least a couple of inches longer than SWB.
what about cutting the LWB axles to length and then cutting splines to match a SWB CV joint on those ends ?
could this be done ? am I crazy ?
answer the second question first

Going to answer your first first question. The bearing size that is different is in the cover. And you can’t put the aluminum cover on the mag case gearbox.

You could do the reverse of Grady clay’s simplified differential hack. But then you would have early differential guts with the troublesome pinned bolt in your later differential.

Skip the cut and machine step out completely. Have swayaway or mark Williams make you a custom axle. Make is SWB length with splines for the LWB cv joint.

But are we even sure the splines are different? Have you tried to put a lWB joint into your existing SWB axle? There’s a really good axle thread around here. I’ll see if I can find it. It’s 10 or 15 years old but has pictures and length and spline count etc.

[ty901]

Originally Posted by Matt Monson

Skip the cut and machine step out completely. Have swayaway or mark Williams make you a custom axle. Make is SWB length with splines for the LWB cv joint.

the LWB axle is about 4" longer so there's that, BUT the diameter around the spline area is 27mm while the central portion of the axle is 26mm. I know how to contact SwayAway, but not Mark Williams. can you help ?

[ty901]

Originally Posted by Matt Monson

But are we even sure the splines are different? Have you tried to put a lWB joint into your existing SWB axle? There’s a really good axle thread around here. I’ll see if I can find it. It’s 10 or 15 years old but has pictures and length and spline count etc.

oh how I wish it was that easy. SWB axles are something like 26 splines while LWB are 32.

[Matt Monson]

https://www.markwilliams.com/axles.html

I know they make 930 based stuff for sand rails. I had them make custom stuff for me a few times when I was at Carquip. A lot of local drag racers here in CO use them.

[ty901]

here is the / our solution: custom axles. Mark Williams makes HP race type axles only ($460 ea.) Brian @ Sway Away does this as well but also offers axles for a more "normal" horse power application (~ $360 ea.) our samples were just shipped to S.A. we need to verify the new axle length. the later output flanges are about 10mm shorter. I'm not sure what the side to side measurement is as mounted on the trans. at least we've reached the home stretch
thanks again to all

[geoff_68s]

Are there significant case differences between the SWB 4-speed and 5-speed, or would it be possible to rebuild the five speed gear stack into the correct for the '68 four-speed case, retaining the diff and output flanges?

(this is an interesting thread for me, I have a four-speed in my car now, which is incorrect, so I'll probably be trying to solve a similar problem when I find a decent five-speed to swap in)

[Matt Monson]

Originally Posted by geoff_68s

Are there significant case differences between the SWB 4-speed and 5-speed, or would it be possible to rebuild the five speed gear stack into the correct for the '68 four-speed case, retaining the diff and output flanges?

(this is an interesting thread for me, I have a four-speed in my car now, which is incorrect, so I'll probably be trying to solve a similar problem when I find a decent five-speed to swap in)

You’re describing something totally different. There’s no difference between a 4 speed and a 5 spd case of each kind. But there are significant difference between a mag case and an aluminum case.

[911pcars]

No one has yet mentioned the two types of half shafts on the 911.

Early 911s used a Nadella U-joint on each end. A typical universal joint.
Later 911s, 68 on ? used Loebro CV (constant velocity) joints. Thereafter, the CV joint dimension changed along with the number and size of attaching screws (M10 vs M8).

Not sure of the spline count on the output flange, probably coarse splines on the early versions and a mix of coarse and fine spline on later 911s. I don't have those details.

AFAIK, the gearbox output flanges aren't interchangeable due to the different joints used.

The question then is; will later axles and output flanges on a later gearbox (901 or 915) fit into the side gears of the 901 gearbox? That about right?

Sherwood