Hello, Would like your ideas on the following: my 59 GMC 660 (gas 503ci) heavy duty truck went for a road trip today, first time in twenty years, but offroad exercised yearly. Its 5 spd Spicer has always shifted fine but after a little workout, up some hills, she won't shift into first (shifts fine thru the rest of the gears). I'm thinking clutch rod adjustment is in order, or could it be something else?
Will the transmission shift into 1st. with the engine stopped? How about double clutching with the vehicle rolling slowly? A draggy clutch won't prevent the gears from engaging with the engine stopped, possibly by pushing the shifter toward the 1st. gear position and bumping the starter pedal. If the gear simply refuses to engage, engine running or stopped, you've got an internal problem, possibly with the spring loaded interlocks in the shift tower that prevent more than one gear getting engaged at once. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
After the simple tests suggested: It shifts fine when everything is cooled down, engine running or not....so I'm guessing that when things heat up, it changes the clearance slightly....maybe a slightly warped disc/pressure plate; maybe things not sliding on shafts properly when hot and/or pedal clearance needs tweaking to give a little less free play? It's interesting that the problem was only with first gear....even when hot, it went thru all other gears just fine.
1st. is probably the only gear that's not synchronized. Some transmissions also use that gear for reverse. Try adjusting the clutch for a little less free pedal at the top of the stroke. As long as the throwout bearing isn't riding on the clutch fingers all the time, you're good to go. A little less than 1" free play is plenty. It sounds like the warmed-up clutch disc is dragging on the flywheel and/or pressure plate a little.
Until you manage to get the clutch adjustment process figured out, here's a work-around. When the transmission is in any gear, everything, including the clutch disc, is stopped because the driveshaft isn't moving. Try selecting another gear, maybe second, and then very quickly moving the shifter into first. There might be a slight clash of teeth, but it will be very brief because the countergear won't be able to spin up. That's a trick we used to use on the big rigs with divorced transmissions, like a 4 X 3, or maybe a 5 X 4. Moving 40 tons of truck and cargo around by stirring two shifters without using the clutch except for starting and stopping took some practice, and sometimes we earned the title of "gearjammer"! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Good, thanks Jerry....I like the work-around idea for now, because it seems like it almost wants to go in first when hot....I have a feeling that the quick shift from 2nd to 1st would do the trick. Old truck, been sitting a long time, the situation might get a little better with some more driving.
"Old truckers never die- - - - -they just smell that way!" Ditto for elderly trucks that have had a long hiatus from working for a living! Give that old rig some exercise- - - -if your 503 is like the one I drove from middle Tennessee to Kansas City a few years ago, it can pass anything on the road- - - -except a gas station! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Glad to help- - - -it was a fun ride! The trip home through about 5 states on my Honda Gold Wing was enjoyable, too! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
