915 transmission / LSD question

[mikedsilva]

I just had my 915 rebuilt with new syncros on 1 and 2.
The box arrived back today, but when I went to turn the drive shafts (out of curiosity) while it was on the pallet, they would not rotate.

I tried selecting a different gear, but it feels like there is a mechanical restriction.

The question; should it feel this stiff when turning over by hand? I know before I sent it off, that it would turn fine and drove ok, but that it had noisy bearings.
But now it feels ultra stiff.

What could the cause be?
Incorrect pinion depth?
Or am I not getting it fully into gear by trying to shift merely by grasping the shift shaft by hand?

[mikedsilva]

Well, an update to this initial post.

The box was installed yesterday, and when I went to reverse up the driveway, the car kept stalling.. I thought I had mis adjusted my clutch so did it again.. no, it was fine.
Gave it more revs to get up the drive way, and again it stalled halfway.. this time, the car was stuck in gear, with the clutch pressed in.. if I used my body weight to try and rock the car, I could force it out of reverse back into neutral and it would roll back into the garage.

Finally gave it a massive amount of revs, and shuddered my way up the drive.. clutch dust in the air.
Got it into first ok, and went to take off... really loud gear whine. If coasting, it was quiet but as soon as I cracked open the throttle, and put a very light load on, it would whine its head off.

Got into second, but it grinds and pops out.. have to nurse it home... cannot get back into 1st. need to come to complete stoop, then find first.. get it home.. really disappointed.

The box was just rebuilt by a retired porsche specialist. What could be wrong?
Before he rebuilt it, my only complaint was a VERY loud bearing noise which I presumed was a loose race in the diff housing. The box has an LSD and it feels like in reverse, it is binding up really badly.

I've started the removal process again.. so frustrating.. any ideas what it could be?
Should I pull it apart myself first.. I have done a few motors before and 1 901 box for a 914... But not sure different tools are required.

I am suspecting incorrect pinion depth as the source of the really loud whining.
In the videos below, I was holding my phone and trying to change gear.. the audio isnt the best.. a lot of the knocking sound, is actually from the front suspension.. but you can here the whine.
Apologies for the profanity.

I am gutted.

https://www.youtube.com/watch?v=M0sjodqPcWE

[Walt Fricke]

Mike - by pinion depth, you mean the side to side adjustment you might make after changing the axle bearings in the sides of the transmission? The ones you adjust by the tedious shuffling of the shim pack after you determine the total stack thickness to get it right side to side?

You could, conceivably, change these without taking the transmission out of the car (though it sure is easier with the transmission mounted to an engine stand). But it is hard for me (as opposed to a guy who makes a living rebuilding transmissions gone bad)to see how it is possible to mess any of this up so badly that the transmission basically won't turn over. What does it feel like if you jack the rear up, tranny in neutral, and try to rotate a rear wheel by hand? If it is hard to budge, what happens if you loosen all the bolts holding the side plate in place, to release the compression that plate causes? As long as you don't let the cover come off far enough to expose the O ring, shouldn't dump your oil?

[mikedsilva]

Originally Posted by Walt Fricke

Mike - by pinion depth, you mean the side to side adjustment you might make after changing the axle bearings in the sides of the transmission? The ones you adjust by the tedious shuffling of the shim pack after you determine the total stack thickness to get it right side to side?

You could, conceivably, change these without taking the transmission out of the car (though it sure is easier with the transmission mounted to an engine stand). But it is hard for me (as opposed to a guy who makes a living rebuilding transmissions gone bad)to see how it is possible to mess any of this up so badly that the transmission basically won't turn over. What does it feel like if you jack the rear up, tranny in neutral, and try to rotate a rear wheel by hand? If it is hard to budge, what happens if you loosen all the bolts holding the side plate in place, to release the compression that plate causes? As long as you don't let the cover come off far enough to expose the O ring, shouldn't dump your oil?

Walt,
I have the engine and box out of the car now. When I get home tonight, I will remove from the engine and get it on the stand. I've not rebuilt a 915 before so am unfamiliar with the side to side shims.. I'll report back my findings after playing with the box and turning the shafts. Hopefully, there wont be any permanent damage to my pinion and crown.

[kamaro]

Definitely something horribly wrong inside that transmission. I would contact the rebuilder immediately and let him handle it.

[Superman]

My advice: LSD is not what it used to be. The guys who made the best LSD are no longer around. Today's LSD is not worth your time. Try psilocybin mushrooms.

[Superman]

[mikedsilva]

Originally Posted by Superman

hahaha
thanks, I needed the laugh.

[ClickClickBoom]

Originally Posted by Superman

My advice: LSD is not what it used to be. The guys who made the best LSD are no longer around. Today's LSD is not worth your time. Try psilocybin mushrooms.

https://en.m.wikipedia.org/wiki/Owsley_Stanley

[Peter Zimmermann]

Porsche Wiki

I'm not sure if you're aware of my 915 Tutorial, but this should help! The web site is Redline Technik, but the article might be difficult to locate. Part 5 of 9 is what you might need!

[Dan J]

1) Take it out

2) Send it back

Simple

[175K911]

/\ /\ This /\ /\
You paid someone good hard earned $$ to have the trans rebuilt, it's their responsibility to get it right. And if you open it up yourself you run the very real risk of the shop saying they have no further liability for anything that's damaged.

[mikedsilva]

Originally Posted by 175K911

/\ /\ This /\ /\
You paid someone good hard earned $$ to have the trans rebuilt, it's their responsibility to get it right. And if you open it up yourself you run the very real risk of the shop saying they have no further liability for anything that's damaged.

Yeah, I hear you.

I took it out the car and installed another transmission that I know works, but has no syncro on 1st gear anymore. I am running in a new engine so I want to put some miles on it while I send the other box back.

I didn't open it, however I did drain the oil in preparation for shipping and there is lots of shiny glittery metal in the oil, like you would see in your engine oil after the first run.

Somehow, I don't think that is a good sign!

[mikedsilva]

Originally Posted by Peter Zimmermann

Porsche Wiki

I'm not sure if you're aware of my 915 Tutorial, but this should help! The web site is Redline Technik, but the article might be difficult to locate. Part 5 of 9 is what you might need!

Hi Pete, yes I have downloaded your tutorial.. I don't have any tools useful for transmissions, (just engines) so I am leaving this to the 'professionals' at this point.
Mike

[Peter Zimmermann]

Originally Posted by mikedsilva

Yeah, I hear you.

I took it out the car and installed another transmission that I know works, but has no syncro on 1st gear anymore. I am running in a new engine so I want to put some miles on it while I send the other box back.

I didn't open it, however I did drain the oil in preparation for shipping and there is lots of shiny glittery metal in the oil, like you would see in your engine oil after the first run.

Somehow, I don't think that is a good sign!

So true, that is NOT a good sign!

[mikedsilva]

Update to this thread.. with the help of a friend, we opened the box to discover the problem.
In the below diagram, there is a spacer washer #34.. but the fellow that rebuilt my box had not installed it. Instead, he installed it at the position of the 2 washers #46.
This then caused gear#35 (2nd gear loose) to be too close to gear #33 (3rd gear fixed). Which meant that #35 interfered with washer #3 on the input shaft. The binding was the gear grinding the washer and there was LOTS of metal fragments.


Anyhow, we are in the midst of fixing the error. However, now there is dispute on the 2 washers at #46 on the pinion shaft. For some reason, that picture does not show the roller bearing between those 2 washers.
Also, my builder has a different diagram that shows only 1 washer at that position.

Here is a pic he sent me. I believe that washer #2 in the below diagram, is in the same position as #46 in my above diagram.
Incidentally, my box is an original unit from a 1977 Carrera 3 with LSD.
Which one of us is using the wrong diagrams?

[VFR750]

You have a parts diagram for a 1983 transmission but you said it was a 1977 Carrera 3.0 transmission?

[mikedsilva]

yes I did.
The diagram above for the 74, would that no be a mag case?

[john walker's workshop]

Between the two 46 thrust washers is a roller bearing that is not shown.

[mikedsilva]

Originally Posted by john walker's workshop

Between the two 46 thrust washers is a roller bearing that is not shown.

thanks John.

Should there be 1 thrust washer there, or two?