LSD rebuild-able?
#31
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interesting thread as im having the lsd out of an 86 auto transmission rebuilt at the minute to swap into my GTS 5spd box. i will have to see about modifying the pinion shaft - how much do you take off it steve?
also a question to erkka: can i re-use the existing GTS oil pump without difficulty? i had thought it would be necessary to fit an external electric unit, my mechanic has also said the inbuilt ones might be more prone to failure.
also a question to erkka: can i re-use the existing GTS oil pump without difficulty? i had thought it would be necessary to fit an external electric unit, my mechanic has also said the inbuilt ones might be more prone to failure.
#32
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Gregg wrote:
They are there every time I look
I'll email them to you directly if you like.
Dennis K,
I've come up with a plan to add two additional friction plates to the unit I'll be installing. Details will follow once I buy the new plates and do the install. Can you let me know why your's failed with the additional lock? My friction plates were also completely stripped, but there was a whole lot of failure going on inside there!
Where did you hide them, John?
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I'll email them to you directly if you like.
Dennis K,
I've come up with a plan to add two additional friction plates to the unit I'll be installing. Details will follow once I buy the new plates and do the install. Can you let me know why your's failed with the additional lock? My friction plates were also completely stripped, but there was a whole lot of failure going on inside there!
#33
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Originally Posted by drnick
also a question to erkka: can i re-use the existing GTS oil pump without difficulty? i had thought it would be necessary to fit an external electric unit, my mechanic has also said the inbuilt ones might be more prone to failure.
#35
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Originally Posted by drnick
interesting thread as im having the lsd out of an 86 auto transmission rebuilt at the minute to swap into my GTS 5spd box. i will have to see about modifying the pinion shaft - how much do you take off it steve?
also a question to erkka: can i re-use the existing GTS oil pump without difficulty? i had thought it would be necessary to fit an external electric unit, my mechanic has also said the inbuilt ones might be more prone to failure.
also a question to erkka: can i re-use the existing GTS oil pump without difficulty? i had thought it would be necessary to fit an external electric unit, my mechanic has also said the inbuilt ones might be more prone to failure.
With a flat spot under the gear, the pinion gear receives lube oil as they turn on the pinion shaft, a simple modification would have prevented the failure that John experience. The depth of this Factory pinion shaft was .080
#36
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Thanks Steve!!!!!
Wonder why that isn't a standard
I'm going to cryo/rem a few transmission gears. Any reason not to have the spider gears done?
Here is a picture of the gear set not destroyed.
Wonder why that isn't a standard
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I'm going to cryo/rem a few transmission gears. Any reason not to have the spider gears done?
Here is a picture of the gear set not destroyed.
![](http://forums.rennlist.com/upload/diff_gears.jpg)
#41
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John - perhaps I had the good fortune of getting off the track pretty soon after it happened so there was not quite as much chewing.
Our best guess is the cross-pins (#3) break first, the fact that they are ground in half like lincoln logs gives them a natural fracture point.
Then, once the bevel gears are loose, they are free to climb axially and move about.
I cant quite tell from the photos - is that a 20% LSD you tore up? Mine is (pictures below).
Our best guess is the cross-pins (#3) break first, the fact that they are ground in half like lincoln logs gives them a natural fracture point.
Then, once the bevel gears are loose, they are free to climb axially and move about.
I cant quite tell from the photos - is that a 20% LSD you tore up? Mine is (pictures below).
#43
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They did something like that in the later PSD differentials, where they have a single cross-casting in the center. You can see its much stronger.
We are going this way: I heard from 928 Intl that the "hot setup" was the early (78-84) 40% Limited Slip was better than the Late-Model 20% LSD. 4 frictions disks instead of two, and we can also see it has a stronger core.
Problem is the size difference - the early LSD is wider than the late-model one, even after you transfer the ring gear over.
We took both to a CMM (Coordinate Measuring Machine) and had them carefully indexed so we could accurately locate the ring gear on the 40% LSD unit.
What I've done is make a large spacer to adapt the width of the 40% LSD to the late-model case. Photos below. If it works, you end up with the best of both worlds: the Borg-Warner transmission with the 40% LSD differential.
We even learned that you can re-stack the drive and driven plates in the LSD in a different order than they are now, and you would double the surface area available to the, and raise the LSD to 80% if you wanted to.
They are currently stacked drive plate/driven plate/driven plate/drive plate; and by restacking to drive plate/driven plate/drive plate/driven plate you have the same final assembled dimension, but twice the friction surface.
I left mine at 40% however, because of the 180 and 190 degree switchbacks at Pikes Peak - where I thought the 80% LSD might be too much.
I'll post again if it works - trying to get to at least a DE day or something with this LSD setup before the snow flys.
We are going this way: I heard from 928 Intl that the "hot setup" was the early (78-84) 40% Limited Slip was better than the Late-Model 20% LSD. 4 frictions disks instead of two, and we can also see it has a stronger core.
Problem is the size difference - the early LSD is wider than the late-model one, even after you transfer the ring gear over.
We took both to a CMM (Coordinate Measuring Machine) and had them carefully indexed so we could accurately locate the ring gear on the 40% LSD unit.
What I've done is make a large spacer to adapt the width of the 40% LSD to the late-model case. Photos below. If it works, you end up with the best of both worlds: the Borg-Warner transmission with the 40% LSD differential.
We even learned that you can re-stack the drive and driven plates in the LSD in a different order than they are now, and you would double the surface area available to the, and raise the LSD to 80% if you wanted to.
They are currently stacked drive plate/driven plate/driven plate/drive plate; and by restacking to drive plate/driven plate/drive plate/driven plate you have the same final assembled dimension, but twice the friction surface.
I left mine at 40% however, because of the 180 and 190 degree switchbacks at Pikes Peak - where I thought the 80% LSD might be too much.
I'll post again if it works - trying to get to at least a DE day or something with this LSD setup before the snow flys.
#44
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Carl, what makes you think later style LSD is 20%. AFAIK Porsche calls it same 40% like all 928 LSD. AFAIK number of plates do not mean how much force is transfered. Many BMW have 25% LSD which would be impossible to have if each plate adds 10%. I think % is determined by style of plates and how tightly they are packed.