[Crumpler]

For the sake of time, the story is condensed.
Worf should be applauded for numerous off-line troubleshooting and cross country emotional health sessions.

Manual G28/11 with LS, original to US 86.5, came off hpde season with a strange noise associated with load.
Probably bearing noise, either from my driving or boosted engine or both, but as yet no definitive diagnosis.
Specifics, with video and audio, are posted on RL. To my surprise, no responses over there. I expected at least a troll reply.
It’s currently on my bench with LS out. Pending rebuild.
Anyway.

My quick fix was to take a chance on a used eBay transmission.
Unit is question was from an auctioned 85, eurospec. G28/10. Equipped with LS.
The further intrigue was the LS was done aftermarket, with no “12” code on the transmission case.
While purchase “returnable” for 60 days… I had the same uneasy thoughts any sane person would have.
Perhaps similar to when I wired money to Estonia for a drop in ECU conversion…
It still felt better then groveling before a certain rebuild egomaniac in southern California.

Unit arrived freight, in a pretty sorry state on the outside, but “ok” in general.


LS appears to have been sold by 928 intl. with ring gear stamped November 84.
My hunch was that it was done by a pro, simply playing odds that if set wrong it would be destroyed by now.
Gear compound looked ok for whatever that meant.


Cleaned up and mated with rebuilt TT.


Mounted with transmission cooler:


Test drive last night. All seems well.
The differences:

Smaller volume case. I think about 500 ml. Not sure how, maybe more internal fins in the case. The case dimensions appear the same.

Larger plugs. The G28/10 has 24 mm fill plugs. As opposed to the 22 mm on the G28/11.

Geared lower. It didn’t look like much on spec sheets, but it really does change shift points. I don’t see it as an issue, but interesting. Maybe you guys can educate me on what Porsche was doing there. Maybe taller gears in US to promote higher top speed?

Shift pattern itself is slightly different.
Through previous trial and error, I set everything per WSM. Even with Hans’ link delete, I’m comparing apples to apples.
Reverse and first are further left. You still get smooth 1-2 without guessing, but 2-3 and 4-5 are more kinda stand alone H, overall. If that makes sense.

[Gary Knox]

On the '928GT.com' web site, you'll find that the '85 Euros were 2.73 diff ratio. Higher numerical than any US spec car up until the GT, which was also 2.73. I suspect the diff you removed had a lower numerical ratio, therefore, the rpms would be lower for any set speed than they will be with the Euro tranny. Some of my track driving was with the 2.20 ratio, and some with the 2.54. LOVED the 2.54
Gary

[worf]

Shift pattern itself is slightly different.
Through previous trial and error, I set everything per WSM. Even with Hans’ link delete, I’m comparing apples to apples.
Reverse and first are further left. You still get smooth 1-2 without guessing, but 2-3 and 4-5 are more kinda stand alone H, overall. If that makes sense.

Shift planes further right/left are due to setting up the rear coupler. Nothing else. One spline off one way or the other makes a big difference especially with that mongo-tall lever you're sporting.

2.20 rear-end was always USA/Can for better fuel mileage. RoW of same year got 2.54 or 2.63 (I forget which.)

[Crumpler]

Got it.
Yes I’m looking forward to seeing how this translates to track driving.
Spec sheet just for kicks.


There’s a chance the splines weren’t set WSM previously on the rear coupler Dave, and now they are correct. I could buy that.

Mongo Tall ?
You better break the news to Hans, that’s his short shifter.

[worf]

No doubt my error is due to the fact that your shift lever is running Commando (no carpet, sound insulation, or console.)

[maddog2020]

Why is Worf always focused on everyone's underwear or lack there of status?

[worf]

Why is Worf always focused on everyone's underwear or lack there of status?

Huh?

[worf]

Oh I get it. I once wrote that your 928 running without an under tray was commando mode.

I could have just written naked.

Are you bothered by references to being unclad?

[maddog2020]

no, not bothered by it, just cracking a joke

[Crumpler]

How about another wormhole?

I had a pro tuner recommend higher weight gear oil.
Like a 75w-140.
That was in a scenario where I had not pulled the original tranny off yet. The tentative diagnosis at that point was a knicked gear causing “the noise”.
I assume that was proffered as a band aid to protect the gears while I finished the DE season.

In a world where I don’t want to ever deal with pulling a transmission on this car again, is there any merit to use a higher weighted gear oil as a prophylactic treatment?
Pro’s v. Cons?
What I’m seeing anecdotal is it would inhibit precise shifts?
I’m guessing if there was merit no one would be using 75w-90 anymore.

[worf]

I had a pro tuner recommend higher weight gear oil.
Like a 75w-140.
...
In a world where I don’t want to ever deal with pulling a transmission on this car again, is there any merit to use a higher weighted gear oil as a prophylactic treatment?
Pro’s v. Cons?
What I’m seeing anecdotal is it would inhibit precise shifts?
I’m guessing if there was merit no one would be using 75w-90 anymore.

I got nothin'. Other than: if 75w-140 was so great... why didn't Porsche spec it from day 1 in 1977?

Also, we hear very few reports of 928s grenading transaxles even in the Open Road Races. (This, unlike transaxle Corvettes that shred themselves in a few autobahn runs unless an oil cooler is added.)

But, Mark Anderson did, IIRC break transaxles on his purpose-built track cars.

He might have some perspective on keeping them alive.

[lupo.sk]

How about another wormhole?

I had a pro tuner recommend higher weight gear oil.
Like a 75w-140.
That was in a scenario where I had not pulled the original tranny off yet. The tentative diagnosis at that point was a knicked gear causing “the noise”.
I assume that was proffered as a band aid to protect the gears while I finished the DE season.

In a world where I don’t want to ever deal with pulling a transmission on this car again, is there any merit to use a higher weighted gear oil as a prophylactic treatment?
Pro’s v. Cons?
What I’m seeing anecdotal is it would inhibit precise shifts?
I’m guessing if there was merit no one would be using 75w-90 anymore.

Aaaah, the good ole oil debate, just for trannies… putting on my fake tits and a wig.

Your oil type & grade areprescribed by the manufacturer of the transmission. Your oil weight fully depends on which climate you live in and what is the use of your car. The -140 means is that the oil is thicker at its operating temp. It also means the film will hold better at higher operating temps and will usually have a much higher temperature tolerance. It will also mean the transmission might be harder to shift at higher temps, see old mercedes trannies on V8s (not even sure you got them in the US), they used something like 80w-130 IIRC and at higher temps and under heavy load, the transmission would feel like it’s freezing outside.

Bottom line because I’m a retard: don’t use 140 oil as it flows MUCH slower at operating temp than a 90 oil. Unless you only use the car for track events, I would not experiment here, adding a thermostat operated oil cooler would be my prefered choice.

[Crumpler]

Ok, good advice both counts. Thank you.
I’ll see how things go with 75w-90 and cooler.