| Author | Message | ||
| RichardF Rating: N/A |
Ok guys, need a little help here. I have a 1961 GMC PD4106 bus conversion and I am having trouble shifting the thing. Does anyone have some pointers or advice on how to do it smoothly? Thanks, Richard | ||
| RJ Long (Rjlong)
Rating: N/A |
Take a look in the "Articles of Interest" section of this website. You'll find what you're looking for. And if that doesn't help, I'm available. . . RJ PD4106-2784 Fresno CA PS: What's the VIN on your '06? | ||
| John MC9 Rating: N/A |
In 1st gear: Let out clutch without stepping down on accelerator. Always let it walk out on it's own. Then, accelerate until it reaches it's governed speed (about 15mph). Count "one-two" as you: depress the clutch, shift into neutral, release the clutch, depress the clutch and shift into second gear and release clutch. Accelerate in second gear until you reach the governed speed (about 30-35mph) and again count: "one-two" as you rhythmically depress the clutch, shift into neutral, release clutch; depress clutch and shift into third. And again..... for fourth gear. Remember the governed speeds for each gear, you need to know each gear's top speed to be able to downshift into the lower gear. You'd want to bring it 10mph slower than the gear you're about to shift down to, to allow time to shift into it. That is: you'll be going 45-50 in fourth if you wan to shift from fourth to third. Use the same "one-two" clutch pace and the same shifting from gear into neutral into gear. Did I 'splain dat right? | ||
| RichardF Rating: N/A |
PD4106-479 | ||
| RJ Long (Rjlong)
Rating: N/A |
Richard - PD4106-479 was delivered new in July of 1961 as fleet number 100 to Las Vegas-Tonopah-Reno Stage Lines, based in Las Vegas, NV. Based on this, at least for the first 10-15 years of it's life it spent it in the deserts of SW US. LTR was a great company, until it's founders sold it off. The new owners then literally ran it into the ground - it's only a memory nowdays. Used to have a great PM program, too. I often had my coach serviced at their Reno yard, never a complaint with their work. John MC9's description is similar to the article I referred you to. The starting clutch technique is called a "Dead Throttle Start", and it does NOT describe letting the clutch out suddenly. Properly done, you feather the clutch thru the take-up point, letting the idle torque of the engine get you rolling w/o any throttle. Done correctly it can be as smooth as an automatic. Done incorrectly, you can tear up driveline components. HTH, RJ PD4106-2784 Fresno CA | ||
| Phil Dumpster2 Rating: N/A |
Hopefully if this works, here's a picture of a similar coach, to give you an idea what yours would have looked like when new. <img> Or click this link. http://www.pacbus.org/images/pbm172r.jpg | ||
| John MC9 Rating: N/A |
Richardf - As RJ said, never so much as tickle the accelerator prior to, or during the initial clutch release (on take-off). That diesel is powerful and geared to walk off at idle. Just let it out slow and let it walk under it's own power, regardless of incline, then give it the fuel after the clutch is fully released. You'll realize that engine's power the first time you start off on a steep grade without touching that accelerator. I remember being taught not to downshift for passenger comfort, but we all did anyway. Once you get the feel, you can shift up or down without jogging a head or spilling a drop of a full cup of coffee. Just keep in mind, that the engine has to be at the speed it would be, if it was in the lower gear. To shift from fourth to third, you'll have to bring it down to 40-45mph in fourth, shift into neutral, hold the accelerator down until the engine's at max governed rev, then shift into third. It's tricky until you practice it to a science. You should not attempt learning to downshift on a downhill grade; do not attempt to downshift on a grade without learning how to downshift on level ground first! | ||
| ChuckMC9 (Chucks)
Rating: N/A |
As a former grinder, this newly shifting smoothie can give enthusiastic tesitimony to the fine advice offered herein! Downshifting on downhill grades still tricky for me tho. I haven't quite figured out what to do if you 'miss' it and wait too late. (other than stop and start all over again.  ) | ||
| RJ Long (Rjlong)
Rating: N/A |
Chuck - Heel & Toe, just like the race drivers do. Toe on service brake, heel on accelerator. Simple, eh? Just like shifting a crash box, it takes practice. On flat land, of course!!  HTH, RJ PD4106-2784 Fresno CA | ||
| Brian Brown (Blue_velvet)
Rating: N/A |
Yup, RJ's article is "Da Book" on shifting. Read it, learn it, live it. Practice as much as you can. I think it was FastFred that had the idea of putting little "pips" (pieces of colored tape) on your speedo to show the shift points. These would become a very visual representation of when to downshift. My biggest hurdle (and still is): rounding a corner whilst underway. Hitting the brake, revving the throttle, watching the speedo for shift point, steering... ack!! If possible, I try to slow down enough before the corner to snag second gear, but not so slow that I'm lugging it getting back up to speed. It's the tight right-handers that are the trickiest. Missing the shift and practically stopping the bus in traffic to get back into first: priceless! Anyways, shifting the Spicer will become more natural the more you do it. And, at least for me, one of the more rewarding aspects of Busnut-dom. Good luck, Brian Brown PD4106-1175 Longmont, CO Our Bus Site | ||
| RichardF Rating: N/A |
Thanks for all the tips and keep 'em coming! I'm going to go out and play this morning and see if I can put all of this advice into action. Thanks again! Richard | ||
| mclough Rating: N/A |
i had a tach put in and that makes the shifting a whole lot easier. but i have a question on the "dead throtle start ". even on an uphill incline you can just let oout the throttle with out any fuel.?? i always seem to want to give it some throttle and make the front end shake etc.(i know i need to replace front bushings ) but on hills it gets fun. any suggestions, same dts with reverse ? morgan oaausa.com | ||
| RJ Long (Rjlong)
Rating: N/A |
Brian - Lug it (no throttle, just idle) around the corner in third, then grab second AFTER you complete your turn. Far easier to do, and you'll still have enough momentum to not drive the four-wheelers crazy. There's too much going on when making a turn to worry about catching your downshift in the middle of the turn. Far better to let it idle around in third while you watch traffic, your mirrors and where you're going, then downshift after you've straightened it out. And usually, by this point, a simple slight blip of the throttle will put you at the right RPM for second. Try it. (See, I just gave you an excuse to get your toy out again to go play with, didn't I. . . LOL) Morgan - On a dead throttle start, for the vast majority of minor inclines, the 8V71 will get you going w/o any throttle, especially in a GMC coach. MCIs, Prevosts and Eagles, because they're heavier, may not respond as well, and consequently a little throttle may be applicable. All coaches with a stock 4-spd manual can easily burn up a clutch if you apply too much throttle while you slip the clutch thru the take-up point, especially on a steeper incline. If you're creating a front end shake, it's time to do a little investigative work. Is the clutch adjusted properly? (On a GM, this means starting at the front of the coach and working your way back, per DA BOOK.) Is there any oil seeping out of the weep hole on the bottom of the bell-housing? Could be indicative of an oil leak and a subsequently oil-soaked clutch disc, which will have a tendency to "grab". If on a GM, have you inspected the engine bulkhead? If the front end's shaking, that same force is being transmitted into the bulkhead, which shouldn't be moving. If it's moving, it might be cracked - not uncommon on a GM with the 8V powerplant. But before you panic, get your coach out on a flat, level parking lot and really practice dead throttle starts, until you can do them smoothly. If, after several HOURS of practice, the front end's still shaking, then you might want to consider getting your coach over a pit at a shop that's familiar with buses (Luke's, for example), and have the rear chassis inspected thoroughly. HTH, RJ PD4106-2784 Fresno CA | ||
| mclough Rating: N/A |
its the front bushings , and my engine is the 6-71 in a 4104 | ||
| Matlacha Rating: N/A |
Have a MCI 5 and the clutch wants to stick down. Bus has set for sometime but seems to be getting worst...any ideas?? | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
Matlacha, do you have some kind of assist on your clutch? If you do, you'll need to get it's problems straightened out before you do much with the clutch. If you don't have an assist, then you may either have something really bound up or have a bad clutch. There are usually lots of fittings and lots of adjustments to getting it right. Tom Caffrey PD4106-2576 Suncatcher | ||
| RJ Long (Rjlong)
Rating: N/A |
And a grease gun to lube everything properly, too! |