GMC 4905 Mirror Head/Arm

[pabusnut]

I need a new mirror head for my 4905 for inspection.  There are multiple problems.  The mirror is cracked, and the pivot ball in the arm no longer pivots.  The non-pivoting was kind of OK because it is/was in the right position for me in my drivers' seat.

I know this has been covered before, but my search only brought up like 10,000 hits on the "mirror" keyword, and it will be sometime next year before I could read them all, so  I apologize in advance for the re-hashing.

1.  Somebody listed a source for the mirror head itself, which would be very useful.  Could you post it again?
2.  Is there a way to disassemble the ball of the mirror mount inside the mirror arm?  Mine must be welded fast from years of corrosion.  I would replace the ball mount with a new one also if I knew they were available.

I will post some pictures tomorrow, when my teen tech guru is available to help me with the weather(I think it has something to do with getting into a cloud anyhow)

Any and all help is greatly appreciated. 

Steve Toomey
PAbusnut

[GnarlyBus]

It took me years before I learned that my MC-9 had an Allen bolt on the underside of my mirror arm that loosened to adjust the ball. Idk if yours has this or not but I thought mine was seized before I learned about the Allen bolt.

[pabusnut]

There is a cover on the underside of the arm that I am sure conceals a spring and an adjusting mechanism of some kind, but I can't get that off at the moment.  The cover cap is probably at least 1-1/2 in diameter and has a screwdriver slot across the center of the whole diameter.  As I currently don't have a vise, it is hard to hold the arm and try to use an impact screwdriver on the cap.

I had a vise before I moved, and you would think I wouldn't lose something like that, but I did.  I guess I will use my Father's day gift toward a new Harbor Freight vise.

[richard5933]

Rosco makes mirror heads which will fit - they have them with both the pivot in the mirror and those like your where the mirror has just a threaded socket. Look under their transit bus mirrors. Luke was able to order a pair for me. You shouldn't need replacements if broken glass is the only problem - see below.

To free up the adjusting mechanism I kept dripping penetrating oil into it. Never was able to get the bottom cap off, but still got it moving. What I did was wrap the wing nut with a piece of an old inner tube, and used a large adjustable wrench to get a grip on it. Loosen it a little bit, then gently tap on the other end of the shaft with a hammer.

The wingnut shaft is supposed to turn against the adjusting part inside, but what happened with mine is that he shaft started to back out instead. By gently tapping the small end of that shaft as you try and turn the wing nut end it forces the mechanism to turn inside. Suddenly the pivot will fall free.

If the only problem with your mirror head is broken glass mirror, just take it to any glass shop and have them cut a replacement mirror. You might need a spacer behind it since new mirror glass is slightly thinner. I had them cut a piece of plexi the same size while they were cutting for this purpose.

The rubber trim can be rolled off, and there are two screws on the metal retaining ring. Pull the retaining ring and the glass can be removed.

[pabusnut]

Richard,

Thanks for the help!
I was able to get the pivot ball freed up, but not without some other difficulty.  One of the three bolts that holds the base of the mirror onto the mirror head itself broke off in the mirror head.  I guess now I will have to drill it out and hope I can get a tap to work in cleaning out the threads.  No easy out is going to help this bolt.

The mirror head is severely corroded on the inside such that I thought it was filled with dirty sand!  The aluminum still seems to be thick enough to last another 15 yrs or so.  If I can get that bolt out, and a new one in, I will just replace the mirror.  If not, I may have to get a new head.

Steve Toomey
PAbusnut

[richard5933]

For future reference, that mounting plate with the three bolts could have stayed attached to the mirror. The post coming out of the pivot is threaded where it goes into the 3-bolt plate, and it's possible to remove the mirror by putting an open-end wrench on the flat sides of the post and spinning the mirror. Easier to do once the pivot is freed up.

Try and get that broken bolt out. Hopefully you can drill it and use an easy-out type of remover. Otherwise, you may need to drill it out and re-tap the threads.

The Rosco mirrors are okay, but the OEM mirrors with the cast bodies are much sturdier. I had the Rosco on my coach for two weekend trips, and ended up putting the OEM back because the Rosco vibrated too much going down the road.

Worse case scenario, get a new mirror put in there and put it back together with two bolts - at least long enough to get you through the inspection process.

[chessie4905]

Or for more time, cut a pattern out of paper, take it to a glass company. Have them cut out a piece and glue it to the old mirror surface. Should be good enough, at least, to get through inspection.