4106 grinds going in to first

Madmike · June 02, 2010, 10:40:12 AM

I have a 4106 with the 4 speed manual transmission. When getting it started or missing the down shift to first the engine/ transmission is running pretty fast. I have tried to wait for it to go slow, but i find myself grinding in to first with the clutch in. Can some one give me some advice on this. I know how to adjust the clutch but have only given it a turn or two. She also shudders when starting out of first. This is a new clutch and i want to be careful with it.

Chopper Scott · June 02, 2010, 10:53:01 AM

I can't say for sure on your bus tranny but on large truck, 9 and 13 speeds, there is a tranny brake that stops the tranny from turning when you fully depress the clutch. The friction from the throw out bearing will turn the main shaft while it is in neutral. A lot of times they get wore down rapidly by people engaging the clutch all the way to the floor when the vehicle is still moving. One shouldn't fully depress the clutch in those instances. The tranny brake has a small friction pad on it and it can wear out quickly. Someone wiser than I will better inform you.

lostagain · June 02, 2010, 11:40:42 AM

I don't know GMs, but most MCIs in the 60s and 70s had the 4 speed straight cut trans. with no clutch brake. You put in the clutch and gently push the stick toward 1st gear until it slows down enough to engage. A lot of drivers weren't so gentle, but those trannies are pretty tough to withstand the abuse of hired drivers.

The clutch brake such as in the 102D3 with Eaton-Fuller 7 speed is very nice, because you can sit at a red light in neutral with your foot off the clutch, then easily find 1st gear when the light goes green.

JC

Len Silva · June 02, 2010, 11:49:54 AM

If everything is properly adjusted and you have the right oil in the transmission and the idle speed is low enough, it can take 30 seconds for the tranny to slow down enough to engage first.

If you missed the downshift into first at a light, try putting it into second or third to get the gears stopped, then into first.

If that doesn't work, then grind me a pound.

luvrbus · June 02, 2010, 11:58:06 AM

All of the 4106'S I have been around which is not many have a clutch brake you can cut it half into and install a new one without removing the transmission.

good luck

bevans6 · June 02, 2010, 11:58:25 AM

I'm not a GM expert either, but there are two fundamental issues. One is gear inertia and the other is clutch drag. the gears inside these things are huge. First is about a foot in diameter and probably weighs 30 lbs all by itself. It is constant mesh with the lay-shaft gears, so they are all spinning too. They are constant mesh with all the other gears, the whole mess is spinning happily away. that is a lot of rotating mass that really would prefer to keep rotating. What slows it down is friction, from the oil, the bearings, the gears meshing. It actually takes a fair bit of torque to actually turn over a 4 speed spicer that is in neutral. The GM where notorious for hard engagement of first gear, to the extent that some people would start the engine in first, anecdotal story. My bus it takes about 15 seconds to slow down to where I can engage first without noticeable grinding. I let the dogs on the sliding clutch inside there kind of rub on each other a bit, very little force, it helps a bit. Also, just leaving the transmission in any other gear while you come to a stop, then shifting directly to first quickly with the clutch down will work fine. You don't have to finesse a downshift to first if you are coming to a stop - just stop then shift. Of course that means you have to keep the clutch in and that's a different story..

The second point is clutch drag. The clutch has to disengage fully, smoothly, and the input shaft has to be free to rotate inside the pilot bearing. Many of the clutches have to be set up on installation so that the fingers are all the same height, and they are engaged by the throw-out bearing equally. If some are not fully engaged, the clutch will drag. With a new clutch, making sure it's installed right may be a last option. Juddering I always put down to a dirty clutch/flywheel/ pressure plate. Or glazing, or just new.

Hope these ideas help.

Brian

Dreamscape · June 02, 2010, 03:49:33 PM

We have a 4 speed Spicer in our Eagle. I have the same issue, but at a stop I just shift to second then to first or just slowly slide it in to first waiting for the gears to slow down. You just have to be patient, and yes I have ground a pound a time or two.

Paul

OneLapper · June 02, 2010, 05:18:28 PM

Quote from: bevans6 on June 02, 2010, 11:58:25 AM
The second point is clutch drag. The clutch has to disengage fully, smoothly, and the input shaft has to be free to rotate inside the pilot bearing. Many of the clutches have to be set up on installation so that the fingers are all the same height, and they are engaged by the throw-out bearing equally. If some are not fully engaged, the clutch will drag. With a new clutch, making sure it's installed right may be a last option. Juddering I always put down to a dirty clutch/flywheel/ pressure plate. Or glazing, or just new.

Hope these ideas help.

Brian

BINGO! I currently have two complete 4106 drivetrains strewn all over a garage. My 4106 had a "new" clutch, too, but the PO didn't replace the friction plate on the flywheel, or the intermediate plate, or throwout bearing, or the pilot bearing (seized btw), or adjusted the pressure plate fingers.

Here's a picture of the fingers and the uneven wear on them

Here's a picture of the uneven wear pattern on the pressure plate disc because the fingers were not adjusted correctly. The 12 o'clock position is heat checked from dragging, and the 6 o'clock position still shows the original machine cross hatch.

The second engine that had a bad clutch in it actually had a completely BRAND NEW clutch installed! The fingers were even, but all of them were a half inch out of adjustment! The clutch never disengaged. Here's a picture of the destroyed clutch disc

So my question would be, if I were you, "Who did the clutch replacement?". Did they truly know what they were doing?

I'm installing a new clutch and I'm following the manual to the letter. I'll let you know how it turns out.

zubzub · June 02, 2010, 06:31:23 PM

My first thought when I read your thread title was ....yeah....so..... But since it's bugging you:
If you're clutch is properly adjusted and as long as the idle is slow you should be able to sneak it in there as you go from 2nd to 1st and are braking at the same time. I've done this with many nasty old transmissions over the years and the 4 spd spicer on my '04 (pretty close I figure to yours) also lets me slip it in as I brake to a stop. If you miss it going back into 2nd and trying again sometimes works....and of course the ultimate is stopping the engine, sticking it in 1st then starting the engine. This will always work. Good luck, but really a little practice and patience and you'll be surprised how one day you won't have a problem at all.

Chopper Scott · June 02, 2010, 07:43:26 PM

So I'm taking it that Mike's particular tranny does not have a brake? I guess that would somewhat surprise me but we all learn as we go.

gus · June 02, 2010, 09:31:51 PM

No clutch brake on these old guys.

I shift down just as the bus comes to a stop. If I miss I stop the engine, stick it in 1st then start the engine.

Sometimes in cold weather I can get it into first after building up air press in neutral, but not always.

I don't think it is going to go away. I just live with it.

PCC · June 03, 2010, 08:17:49 AM

Quote from: Len Silva on June 02, 2010, 11:49:54 AM
If everything is properly adjusted and you have the right oil in the transmission and the idle speed is low enough, it can take 30 seconds for the tranny to slow down enough to engage first.

If you missed the downshift into first at a light, try putting it into second or third to get the gears stopped, then into first.

If that doesn't work, then grind me a pound.

I cut my teeth on a 4104 and the shift into first was either done as you were stopping, or slowly, letting the gears gently grind to a halt.

I doubt it will have anything to do with the adjustment of the clutch. But I do know that the transmission they installed in those days was tougher than most bad drivers.

Madmike · June 03, 2010, 08:22:52 AM

Thanks for answering my question. I will give the 2nd gear first a try. As far as the clutch adjustment, I know where to adjust it but when do you know when?

zubzub · June 03, 2010, 08:34:26 AM

The clutch adjustment referred to above is the adjustment during the installation of the clutch. The big knurled knob that adjusts free play in the clutch release mechanism (clutch pedal et all) has a spec for it, but the basic idea is that when the clutch pedal is not depressed there is just a little play to ensure the clutch isn't being dragged. With the pedal depressed the actuating arm of the clutch should travel full distance. If it can't there may be too much play in linkage (PITA).
BTW it sounds like you are just getting used to a crash box. but you should still get the full set of manuals for your bus and get to know and maintain all systems ( or pay big $$ to have someone else do it).

Madmike · June 03, 2010, 08:40:47 AM

I have all the service and parts manuals but they are very large and take a ton of time. So for the quick questions i have been comming here. I will put more effort in to reading them. I wish they made a learner manual for like the new grey hound driver to study, kind of like a get to know class. I am in the st. louis area so if any of you want to give a class let me know.