Spicer 4-speed shifting

[richard5933]

Can someone help me relax a bit about shifting our new 4108? Every time I drive it I feel like I'm taking years off the life of the transmission.

When the transmission is warmed up, I can usually up shift with no (or minimal grinding). Downshifts are really frustrating for me - 4th to 3rd is not too bad, but if I have to go down to 2nd in traffic I usually have problems doing so without grinding. On a cold transmission, even the up shifts can be problematic for me right now. Seems like this things has a really steep learning curve. Oddly, the one thing I have no problem with is getting into first - I just know that I have to do this as I come to a stop and then not move into neutral.

I have read many threads on this. I think that I have have a cognitive understanding of how things are supposed to go. Problem is that I have not yet developed the physical technique to get things going smoothly. Making it more difficult is the air throttle which seems to remove any sense of feel from the accelerator.

Anyone have any tips?

Anyone know how much abuse one of these 4-speeds can take before needing an overhaul?

[Utahclaimjumper]

 Richard,,, to bad you live in the state of Wisquito,, if closer you could attend the Western GM Coach annual rally at Quartzsite AZ...A certain gentleman we call RJ ( a rogue on this board) has been pushing GMs with crash boxes around half his life and is good at tutoring newbes in the art of crunching gears.>>>Dan

[dtcerrato]

We've been crashing our Spicer four speed for almost 40 years. These are called bullet proof transmissions and we have had zero issues with ours. Clutch free pedal is related to crash box gear grinding. We find if the clutch free pedal is adjusted to it's minimum, there is less grinding of the gear train. If free pedal is sloppy and closer to "more than you need" then grinding becomes worse. Couple with those statements - the single most helpful thing we did for our Spicer 4 speed at the direction of the late Dean's Coach, was to run a pure synthetic 50 wt. Gear oil. With that change many years ago, & the fine tuned free pedal adjustment, the amount of gear grinding we get is minimal & of no consequence to the longevity of the crash box. By the way they don't call it a crash box for nothing...

[luvrbus]

A tach helps or mark the speedometer,I never found those hard to shift because I grew up in the era of the old square gears my dad owned trucks that had 4 speeds and some with the 5 speeds with the Brown Lipe 4 speed auxiliary transmissions those were treat lol.

The 1st modern 5 speed transmission I drove I thought something was wrong,you will get the hang of it since it's not heart surgery just takes time      

[RJ]

Richard -

Welcome to the world of GM wet-clutch 4-spd manual transmissions!!

Over the years I've seen many an experienced stick-shift jockey brought to their knees by these Spicers, so you're not alone.

Send me your email address in a private message and I'll send you an article (in .pdf format) I wrote a few years ago about shifting these beasts.

Dan -

Thanks for your kind words, they're appreciated.  See you at Q!

RJ

[chessie4905]

Soon you'll be kicking yourself for letting that 4106 go. There was the automatic with everything you would need. You'll end up paying at least twice what that coach would've cost to bring home. Plus, coaches with manual transmission are getting scarcer and less desirable, esp. value wise.

[richard5933]

Soon you'll be kicking yourself for letting that 4106 go. There was the automatic with everything you would need. You'll end up paying at least twice what that coach would've cost to bring home. Plus, coaches with manual transmission are getting scarcer and less desirable, esp. value wise.

No matter how I ran the numbers keeping the 4106 just didn't make sense. There were just too many issues to deal with, and each one had expenses attached. In the end, we decided that a V730 with over 150,000 miles on it just wasn't worth the money it was going to take to bring it home. For now, I'm focusing on learning to shift the 4-speed. Down the road if I decide I must have an automatic I'll figure out how to make it happen. Nothing's permanent, and nothing is beyond future changes.

[chessie4905]

Your model should have a countershaft brake. Two small clutch plates connected to countershaft to assist in shifting. They work when pedal is fully depressed to slow or stop gears. The only time pedal is fully depressed is when just selecting 1st or reverse. Otherwise can interfere with normal shifting. This assumes there is still lining on those plates and they aren't worn out.

[bevans6]

I learned how to shift the Spicer using RJ's memo.  The key is to double clutch every shift and match engine speeds with every shift.  I have tricks I learned.  When up-shifting, the engine speed has to fall to match the new gear, so take your foot off the accelerator, clutch into neutral and pause, clutch again and go into gear - the length of time you pause depends on the gear.  First to second is a big jump in gear ratio, I would pause for a 1 - 2 count.  Second to third is a smaller jump, I would pause for a 1 count.  Third to fourth, I wouldn't pause at all, just a deliberate double clutch and into fourth.  Down-shifting I only did when necessary.  If possible, I would do it by speedometer.  I knew the governed speed in every gear.  When I reached the governed speed for the gear I was going to shift to plus a few MPH (plus a few because if I was down-shifting I was slowing down, and I needed the engine speed to match the new gear when I got to it) I would clutch to get out of gear and into neutral, I would stab the accelerator hard to bring the engine up to the governor, and then off the accelerator and clutch into the new gear.  I was using speed and the engine governor to help match engine speed to gear ratio.  In normal driving I would roll up to a stop sign in fourth gear, clutch in at around 20 mph, and shift into first from fourth once I stopped.

Here is a picture of what you are grinding.  The engagement of the gears is by sliding a hub over those tiny little splines in the center of the gear.  You can see the splines on the main shaft that the hub (the gear with the straight cut teeth is the sliding hub, the gear with the helical cut teeth is second gear) slides on and the nubs on the gear itself are about 1/4" wide and tall.  The hub slides over those little nubs to engage the gear and lock it to the main shaft.

[roadrunnertex]

To bad you don't live near Oklahoma City,OK.
Fred Rayman is the old master when it comes to shifting the old Spicer 4 speeds.
My 4905 was eating my lunch when it came time to down shift or up shift.
Fred said I can shift it no grinding let me show you.
Fred was a master at shifting the old GM's.
Of course Fred was a real bus driver as he had driven many miles for Oklahoma Transportation Company and the fleet was all GMC Coaches.
Later my 4905 got a V730 and it was a wonderful coach to drive.
Ask R J Long!
JLV/RRTex.

[Nel]

After owning the 4104 for about 4 years and driving it for 3, I actually enjoy the 4 speed and when you get the hang of matching the engine speed with the trans / road speeds, most of the time you don't even need the clutch, take your time and the best way to get the hang of it is just drive. For me the only issue is sometimes you cant hear the engine since it's 35 feet behind you , but all is good, Love my 4104.

[luvrbus]

He is shifting with a oil clutch with a clutch brake if he pushes the clutch to far down it screws the shift up, it only takes 1 inch of down pn the pedal to disengage a oil clutch if everything is adjusted right.Oil clutches have been around for years not just on GM buses and are still used today a to heavy weight oil is a killer on one shifting,he will get it time     

[richard5933]

Thanks to RJ for the article and to everyone for their tips.

I guess the one biggest thing I need to work on is timing and getting the engine speed up higher when downshifting. With the air throttle there is no feedback through the pedal. Hard to hear the engine as well. I've been afraid of over-revving the engine. Sounds like that's not a problem and may be what's causing my downshifting problems. The upshifts are most likely a timing issue. Going to need more practice - guess that's just one more excuse for taking out the bus even more often.

[bigred]

Richard,the thing about double clutching is to make sure you get your revs up while the clutch is out .In other words when you need to change gears ,depress clutch ,move shift lever to neutral THEN rev the engine to get the r p m up (you don't have to floor board it )move the shift leaver to the selected gear .At least that was what always worked for me .Going into 1ST should the need ever arise is a little trickier.The best deal here is to do the way our old school bus driving instructor told us to.Wait till the bus stops moving the instant it does cram it into first and proceed!! lol

[luvrbus]

You can adjust the air throttle to fit your driving habits and response time that is no biggie if you feel that is the problem,that engine probably has a throttle delay also that you can adjust