Alt Shaft stripped HELP

74cookiecutter · 74cookiecutter's Garage

I started to title this post. "Does this shaft look short" but I reconsidered the possibility that Zman might jump over from OT and edit my pics.
So...
I was replacing my outer pulley half with a new stock 96mm outer half. It didn't fit with my fan belt.

(My current outer half is the 82mm w smog pump belt groove. why, since the car never had a smog pump? and why wont the orginal spec pully fit with the correct 710 or 725mm fan belt? (earlier post that went unanswered!))

when I went to put the old pulley back on I stripped what was left of the first three threads on the shaft.
Unfortunately that's as far as the nut goes on when it was on tight.
I noticed a month ago that the shaft was only long enough to go half way into the nut and wondered how long this could last.
Apparently not long.

can I just replace the shaft or do I need a new Alt?
Either way, I know I need to take the fan out and then the Alt. right?
I tried to remove the fan without loosening any fan housing bolts or fasteners but no luck. Losened the fan housing strap, no luck.
I noticed the key hole on the edge of the shaft and wondered if that had something to do with easing the removal of the fan?

Can someone point me to a thread that specifically adresses this removal process and tell me what kind of damage i'm in for $$$ to fix the shaft issue?

TWork, rlane, bigchillcar I've noticed you all have some experience in this era 911 engine and the Alt/fan problems.

john walker's workshop · 05-10-2006, 06:26 PM

the housing, fan and alt are removed as a unit and disassembled on the bench. there are thread files that may smooth out the boogered threads, and a thread die ccould probably get them straightened out enough to get a nut started again, but if they didn't even go all the way thru the nut, you may be screwed. the shaft is the alternator's rotor basically, so the alt would need to be replaced if all else fails. i've used a smooth stone grinder to remove the offending threads, but that may not leave you with much.

74cookiecutter · 74cookiecutter's Garage

thanks, Yes i thought about trying to rework the threads, but since the ones that are rolled over and smoothed are the only ones that the nut covered it would be a moot(sic) point.
With that said. what bolts, nuts clamps have to come off to get the assembly out?

david lipman · 05-10-2006, 07:13 PM

BTW: bought a rebuilt alternator on ebay for about $100 that worked out well, and noticed the guy advertises a lot. I think his name was "shant" or something like that.

74cookiecutter · 74cookiecutter's Garage

I need to pull mine out to find out what I have. Given that this engine was heavily reworked around 83 I am finding parts that I thought would match are not fitting or have been upgraded to the improved version. Neither my dad nor the prior owner provided quite enough information to make working on her easy.

If I can, I'll avoid the 350+ hit for the reworked/new alt. But I don't want to be doing this job twice either.

My trip to the hurricane ravaged Gulf Coast last week made me a little concerned about purchasing used parts with unknown origins.

74cookiecutter · 74cookiecutter's Garage

Hey. It's wonderful to read. I just found Waynes instructions for this process in 101 projects...

74cookiecutter · 74cookiecutter's Garage

OK, I got the damn thing out. Man that was a lot harder than I anticipated.
And I've found more problems. AKA.. more places to spend money I don't have!

The Alt shaft, which was barely long enough to start with, had its key frozen to the shaft. Can someone take a look at these pics and tell me if this looks like the correct shaft design? If it was/is/was then why is the Nut not going on any further than halfway?

To add to my concerns... the Fan Housing has a crack on the inner support ring. I doesn't go through the wall of the inner ring but it sure is long(see pic). Should I be concerned? Since this is a non-moving part I'm tempted to ignore it or just JB Weld it.

As if those issues weren't enough.
I am concerned that the strength of the Fan center pulley support piece has been compromised. The pulley support piece (with the flat sides and round top and bottom) has tool marks beside it where someone took a rotary blade and cut down each side of the support piece and slightly into the face of the steel. Plus the pulley has washed a groove in this piece from when it was put on without the shims(see pics). and now there is about an 1/8th inch of play in the the rotation of the outer pulley half (When tightened it doesn't appear to move though.

john walker's workshop · 05-11-2006, 09:19 PM

that looks like the old 50A unit which is hard to find as a rebuilt. you may have to go new. the core isn't rebuildable with the threads wasted like that.

74cookiecutter · 74cookiecutter's Garage

Which Alternators will fit and provide the correct shaft length? This alt shaft was about 10-15mm too short.
Will I be facing the same short shaft problems on all the new ones?
Or is there something wrong with this unit?
IE: been reworked/modified or is it the wrong unit for my fan?

Evans, Marv · 05-11-2006, 09:50 PM

I think John is right about the rebuil situation. Looks like somebody whacked the end of the shaft with a hammer or something. If that's the case, I'm surprised the nut could be threaded on at all and the bearings haven't gone. You should look around for a rebuilt one outright. That crack in the housing is a big one. You can have them welded, but it usually isn't pretty. But as long as it works, it's OK. Besides, if that's a 50A unit as John says, the housing will only take another 50A alternator. They're too shallow to put a 70A unit in. So you probably need to look for a 70A housing and alternator. The fan can probably be used. but basically I think you are screwed. Also I hope you didn't mess up the threads on the nut. It's a m16x1.0 and really hard to find. To get it to where you're not going to have problems, you're going to have to spend some money. Start with some WTBs on the for sale board. Good luck.

74cookiecutter · 74cookiecutter's Garage

I thought that was the way this thing was going to shake out. BTW the end of the shaft wasn't bent or as bad 10hours ago. I was the one who beat the end of the shaft till it mushroomed and bent. I figured what the h***. The nut wouldn't hold those last three threads, the shaft was too short and two people already said I need a new Alt. (3 strikes, you're out) What is the depth required for the larger Alt? I was looking at this one in Pelican:Paris Rhone 75 Amp New Alternator, 911/911 Turbo (1975-83)
Could the old Alt have been a larger unit and therefore left too little shaft sticking out?
Am I correct in assuming the housing will require TIG welding since it is Mg?

bigchillcar · bigchillcar's Garage

robert...maybe check out what david lipman suggested above: find another 55 amp marchal alternator if you can (like mine)..get the housing that you have tig welded and just use it. unless you plan on running a big amp with stereo, you don't have to have the 70 amp alternator that requires the new housing. i'd stay cheap and look for a replacement 55 amp. next question is can the fan be salvaged. maybe the guy you mentioned today with a tig can correct the cuts and grooves in the fan..then i think you'd basically be good to go as cheaply as possible..but the bottom line is that i think it will work. sent you a pm..ask grady's opinion on the fan.
ryan

david lipman · 05-12-2006, 04:20 AM

I've repaired a housing crack with JB-Weld, seems to hold ok. Can't see your crack from the picture, but might be worth a try since its not all the way through...yet. Magnesium is porous, so good for epoxy, just clean well.

david lipman · 05-12-2006, 04:22 AM

Also, I've seen entire 7R housing/fan/alternator assemblies on E-bay for under $400

Jim Sims · 05-12-2006, 05:31 AM

"I was the one who beat the end of the shaft till it mushroomed and bent. I figured what the h***. "

If you did this action with the alternator still installed this may be the origin of the fan shroud (fan housing) crack. Magnesium alloy isn't very tough.

Evans, Marv · 05-12-2006, 07:39 AM

Jim may be right, although it looks like there is some oil in the crack at the beginning, so it may have been cracked a little to start with and expanded later. I'd definitely go for welding it. Although the way that glove is positioned when it fell may be a bad omen for this project. I also think Ryan's suggestion is a good way to go too if you don't need the extra amperage. I had my alternator rebuilt for $90, but now yours isn't any good for that, nor is it any good as a core.

jtfreels · 05-12-2006, 08:18 AM

sent you a PM

74cookiecutter · 74cookiecutter's Garage

Hey guys, I had the fan housing off before the brutality began.
It ain't my fault it's cracked!
In hine sight I do regret trashing the Alt but, I'm not sure why its shaft was too short anyway.

Another mystery I may never solve.

D lipman- I checked e-bay last night and nothing there then. I will keep looking though for entire assembly incldg Alt. My main concern is selecting an Alt that will fit what I have and provide the correct shaft length for my fan setup. If any one has there Alt out and can take some shaft measurements (the Alt shaft) I'd appreciate it.