GM 4104 Spicer GRINDS GEARS BAD

[John T]

  My buddy has a 1960 4104 GM Bus RV with a 671 Detroit and Spicer 4 speed tranny with a dry single disk non braking (I see NOTHING in clutch or bell house that looks like its any braking mechanism??) push type clutch. He has had problem for years that gears had to grind bad to put tranny in gear so he just replaced:

  Clutch disc and pressure plate with 6 adjustable fingers,,, New Throw out and Pilot Bearings, both fit and work correct,,,,,,,Disk is on right direction and hub fits n slides sweet and smooth on input shaft,,,,,,,,Flywheel turned/machined down smooth,,,,,,,,,,The two side bushings in bell housing (where big bell housing arm pivots when pedal is depressed) are new and tight,,,,,,,Currently the fingers are adjusted so there's like 1/8 inch between throw out bearing when at rest to the fingers (so throw out don't turn all the time DUH) but we have tried like 1/16 or less clearance yet NO HELP,,,,,,,clutch linkage adjustment set tight so as soon as  pedal starts down the throw out tightens up against the fingers,,,,,

   BUT WHEN PEDAL IS ALL WAY TO THE FLOOR HE ONLY GETS LIKE  ½ INCH OF THROW OUT TRAVEL (1/2 inch of throw out depressing fingers to disengage clutch)          Id like to see it move maybe ¾ to 1 inch for more spring depression???

If started in gear with pedal depressed the bus dont move (but hey it weighs what 10 tons lol) , it releases enough for that, but still grinds bad if put in Neutral then try to get in gear.


  QUESTIONS:    1) Is ½ inch enough travel so fingers move far enough to disengage
                                  clutch?
2)   How critical is the 6 fingers adjustment??? We screwed them way
      out so theres only 1/8 inch (even tried less then 1/16 still no help)
      between them and throw out at rest trying to maximize travel when 
      pedal is depressed to push fingers deeper.  They were way back
     from rebuild shop, but as set there was like ¾ inch before throw out 
     ever contacted them, so we adjusted them more outwards so they
     will be closer to throw out  when its all the way back.
  3) They supposed to use 40 wt oil?? His is much thicker

Our plan is to fix any slop or wear in clutch pedal and linkage especially rear where the cross direction pivot is TO TRY AND GET MORE THOW OUT AGAINST FINGERS TRAVEL WHEN CLUTCH PEDAL IS TO FLOOR

PS Today we checked and tightened and adjusted and took up about any and all slack we found in the linkage from pedal all way back to bell housing (after today I no longer think linkage or its wear is the problem) when the pedal starts to move the big bell housing lever arm moves buttttttttt I still don't believe the throw out travels far enough back to front i.e dont push fingers deep/far enough

PS FINGER ADJUSTMENT: We have them adjusted outwards a bunch so they are closer to the throw out when its all the way back in full retracted rest position. If they are moved farther towards pressure plate all that does is we have to take out more rod linkage slack to bring the throw out up closer to the fingers again. HOWEVER they are alllllllll adjusted equal distance from throw out.......
WHY ISNT IT RELEASING ?  GEARS STILL GRIND BAD,,, PLEASE HELP BEFORE IT DRIVES ME TO DRINK AS I HAVENT ENOUGH HAIR TO PULL OUT LOL

[zubzub]

Setting up the clutch is fairly complex in da book.  I have yet to do it so I can't help there, I can say that there are enough details in da book to suggest that you need it to set up the clutch properly.  ie not a seat of the pants operation.  I tried to do a sanpshot of the section but cvan't get all the info into a snap, if you have a good email I can send you the entire manual (I think, not sure if perhaps the file is too large) others here also may have a way to send the manual to you.

[John T]

  Thanks, my e mail is    jmn50@msn.com        I appreciate the help but DO NOT EXPECT YOU TO go to more trouble then necessary.  Monday Im gonna re set the fingers close to where they were when we picked up clutch at rebuilder which is about paralell with the clutch disk, they are way out from that now closer to throw out...

  John   jmn50@msn.com

[zubzub]

check your spam filters I sent it through send big files.com

[Damn Yankee]

My 04 did the same thing and it drove me crazy. The first thing I did was go to a lighter weight oil (40W is ok) I also poured in an engine additive, like slick 50. This made a HUGE improvement, BUT.......after it set for a day or more it would still be imposable to get it in gear. What I learned was to start it in gear and let it run for a minute then pull it into neutral, then it was no problem shifting it without excessive grinding. Some grinding is to be expected cause it's just the nature of the beast.

[NJT 5573]

Bob is right about trannys with straight cut gears loving Slick 50. It will stop the noisiest 13 speed overdrive unit from screaming at you.

I use it in my 13 speeds all the time. It does have one problem though that is a trade off. Slick 50 comes with small chunks mixed into the oil. In time the small chunks will work under a seal, usually at the output shaft and it will start leaking. I just let them leak, they don't leak real bad for the most part and I hate to change the seal because the new one will eventually do the same thing.

I have the same luck in the engines, it is usually the front crank seal or the rear crank seal that leaks. Apparently the seal won't exert enough pressure on the Slick 50 chunks to smooth them out and they just hang in the seal making it leak.

[Tony LEE]

With this gearbox and clutch you have two choices. Build up your leg strength so you can slip it into first as you come to a stop and then hold the clutch down until the traffic lights change - OR - accept that it WILL grind and just ease it into first slowly and let the grinding slow the gears down enough to engage.

BTW - when the box is cold there is no problem and it is only when the oil is hot that the gears keep turning. I can't see how shifting to a low viscosity oil would improve things. Higher maybe.

[Just Dallas]

Removed

[bevans6]

If you are considering switching to a gear lube for your spicer, remember that along with having extreme pressure additives to allow the sliding contact of a hypoid gear, the gear lubes are rated on a different viscosity scale.  90 weight gear oil is equivalent to about 50 weight engine oil.  I don't know of anything bad about running a gear oil in a transmission.  We run gear oil in all our race transaxles, since they share the oil with the differential.  My spicer doesn't have a pump, it just splash lubricates and depends on splash to get oil into the filter trap section.

http://www.bobistheoilguy.com/visc.html

Brian

[Len Silva]

In another post I put the maintenance manual online at http://www.manuals.lenstudio.com/.  Everything you need to know about the transmission and proper clutch adjustment.  The clutch section begins on page 116.

One thing to note is that if the pressure plate has been resurfaced, then the clutch assembly must be shimmed by the amount removed.  The fingers should be 1-3/8" from the clutch assembly surface.  I think that the only way to do that correctly is with the clutch assembly on the bench.

Follow the book and adjust everything from front to back per specs.  That made a tremendous difference in mine.  Lot's of adjustments had been screwed up by PO's.

[bevans6]

Len, I down-loaded the manual and read the clutch section.  I have no idea why, I have never even seen a 4104!  let alone it's clutch...

I read about how the clutch fingers need to be adjusted to 1 3/8" from the plane of the clutch cover.   the picture shows it really well indeed.  They said to do it after the clutch was installed on the flywheel with the clutch disc installed as well.  that would mean that the thickness of the clutch plate would affect the height of the clutch fingers to some degree, so i can only see doing that on the engine.  The fingers have to be within .030" of equal height too.  Tricky lying on your back under bus in the dark, maybe on GM's the clutch is more accessible.

Fun to read about, anyway!  Probably less fun to actually adjust...

Brian

[RJ]

Tricky lying on your back under bus in the dark, maybe on GM's the clutch is more accessible.

Brian -

Unlike your MCI, the GM 4104's engine sits sideways across the back end of the coach.  With the transmission out, you can easily sit on a stool with plenty of light to adjust the clutch fingers.

When the transmission's installed, minor clutch adjustments can be done by simply opening the curbside transmission access door, the wheel is less than an arm's length away.

GM really designed the '04 for serviceability - probably one of the best in this regard.


John T -

If you haven't already, download the manual and follow the procedures outlined by the factory.  After that, and resetting the clutch fingers to specs, let us know how it works.

Some grinding is normal, but nothing like the wet-clutch models that came later.

Sometimes slipping the gearbox into 3rd or 4th and then sliding it over into first reduces the noise to a minimum.

FWIW & HTH. . .