HI, I am new to this sub and have just purchased the manuals for a 1973 P8M-4905A that my father was using as a tour bus back in the day. The bus has been sitting for quite some time and was in need of a little love. After giving it an oil and filter change on both the engine and transmission plus a fresh set of batteries and fuel. I gave it a start and she fired right up. Unfortunately, that excitement fell short after trying to get her into reverse. I assumed it was the reversing solenoid, but didn't have much time to locate/troubleshoot before I had to leave. I am currently trying to just get a general idea of the location of each solenoid and relay for the reversing mechanism.
I have searched the forums here for photos of the reversing solenoid and/or relay, but to no avail. I am not near the bus at the moment so all i have is the manual to go by. If anyone has photos of a V730 reversing solenoid and/or part number I'd greatly appreciate it so that I can help get this old girl back on the road when I return. Thanks for any assistance, Michael
A v730 does not have a reversing solenoid it is an automatic with a shift cable and shift tower in the driver's area ,the 4 speed manual transmission does have a reverse solenoid
maybe not enough oil
Shift linkage not getting the transmission all the way into gear?
Check the easy stuff first...
Happy coaching!
Buswarrior
https://www.ebay.com/itm/325183533919?hash=item4bb672f35f:g:88YAAOSw-lhieltW
No guessing. Very specific way to check oil.
Quote from: 1MOFrolla on August 11, 2022, 09:52:27 AM
HI, I am new to this sub and have just purchased the manuals for a 1973 P8M-4905A that my father was using as a tour bus back in the day.
Michael -Help us help you, here.
First question: Does the bumper end of the transmission look like a giant bowl, or is it flat with a large "V" embossed on it? The following info is based on a "bowl" model automatic. If you have a "V" model, send me a private message.
Second question: Does the coach have a gearshift lever? If so, then it's a cable-operated shift mechanism, no electrics involved except for a neutral safety switch at the bottom of the shift tower. The fact that it started right up tells me that the neutral safety switch is ok. Shift cable attaches to the curbside of the transmission, just about directly under the engine bulkhead.
Third question: Is the shifter a toggle switch with indicator lights on the driver's LH switch panel? If so, you've got a "Stone Bennett" shifter mechanism, which is actually very reliable. It consists of the switch panel up front, then an electrical solenoid bolted to the side of the transmission that operates the transmission's shift lever. IIRC, from N, one click forward is D, two clicks forward is 2nd, three clicks forward is 1st. From N, one click backwards is R. It may be the opposite of this sequence, it's been awhile since I futzed with them.
From the curb side, with the transmission access door open, look under the bus just below the engine compartment bulkhead, you should see the shifter mechanism easily - it's just below the transmission data plate above the oil pan. With the engine
off, spray some Kroil, PB Blaster, or Liquid Wrench penetrating oil on the solenoid's "piston" (not exactly the correct term, but can't think of the right name for it at the moment - but it's what the transmission's shift lever is attached to) and let it soak for a little while. After a thorough soaking, using a broomstick or other similar tool, push the piston into the solenoid as far as it will go. Then pull it back out as far as it will go. Do this several times, spraying the piston with penetrating oil with each movement in order to free it up. After it's free, double-check the electrical wiring at the opposite end of the solenoid to make sure it's ok. Can't emphasize this enough - you have to do this with the engine
OFF!As far as the piston's positions go, pushed all the way in is R. One click out is N, two clicks is D, three clicks is 2nd, and all the way out is 1st.
This next is best done with a helper in the driver's seat. Fire up the engine, low idle, parking brake on, transmission in N, and helper's foot on the service brake. For additional safety, the wheels should be chocked at both axles. With your broomstick, push the solenoid's piston all the way "IN" - you should see/hear/feel the transmission go into reverse. Ask your helper to click the toggle switch forward one click while you observe the solenoid. You should see the piston come out of the unit by one click, and see/hear/feel the transmission go back into neutral. Ask your helper to click the toggle forward three times, and you should be able to see/hear/feel the solenoid move the piston all the way to first gear as the transmission responds. Repeat several times to make sure it's operating properly. When you're satisfied, take it for a drive, and test it out on the road. Don't forget your broomstick, just in case it hangs up on you.
Those solenoids are pretty simple devices, and, IIRC, they're rebuildable. If not, Luke at US Coach may still have replacements available. 1-888-262-2434 is his toll-free number in NJ, M-F 9-4.
Fourth question: What oil did you put in the engine when you did the oil change? Detroit Diesel Power Guard 40, Mobil Delvac 1240, Chevron Delo 100, and Shell Rotella T are the most popular, correct, straight 40wt oils for this engine. Multi-weight oils are NOT recommended for the 8V71 in your bus.
FWIW & HTH. . . ;)
RJ
V730 came out in 1977. Are you sure it is a V730?
Hi everyone,
First of all thanks everyone for all the help. It is greatly appreciated. This is far more difficult when you are not next to the bus and don't have someone nearby to check and/or take decent pictures to make this process easier. That being said, I have finally arrived at the bus and am around for a few days to help troubleshoot this now. I'll add photos and take videos of what I see or attempt. For now here are some of the answers to your questions:
The Bus is actually a 1971 GMC 4905A, not a 73 as I previously mentioned.
First question: I have attached a photo, I believe this bus is the Bowl type.
Second question: Yes, Gear shift lever. I guess I was confused by the manual I have stating that you need to hit the reversing switch at the LH driver's side before shifting into reverse. (See in the driver's station photo, bottom switch that says reversing)
Third question: I don't think so if the photo attached is any help to decipher. I am going to try and
cycle the actuator?(piston) and see what luck may bring this afternoon.
Fourth question: Yikes.I went by the recommendations of a Napa servicemember and used 15W-40, ugh. That was pre-manual, but nonetheless. I should have known better. Looks like I will be doing an oil change soon as well. I am ordering a v730 manual today. If you know of anyone with a digital copy, I would be more than willing to pay for that instead of a hard copy. Thanks again for all your assistance.
Michael
It sure looks like a 4905 and the shift lever is a V730 type.
Quote from: 1MOFrolla on August 13, 2022, 12:31:27 PM
Second question: Yes, Gear shift lever. I guess I was confused by the manual I have stating that you need to hit the reversing switch at the LH driver's side before shifting into reverse. (See in the driver's station photo, bottom switch that says reversing)
The manual here is talking about the situation before that V730 was installed - back when it had a 4-speed Spicer manual transmission.
that reverse switch if spring loaded, is from previous manual transmission.
Update:
So I cycled the actuator a few times and then started the engine up and made a few attempts to manually get the transmission into reverse.(by having someone in the drivers seat and shifting into drive, then all the way into reverse using a little momentum to try and jog the transmission into reverse gear) Oil level was checked using procedure from manual and is at or above necessary level. What it sounds like is the reverse gear almost engages and then "slips out" making a rubbing sound. The bus will go into drive and will move forward.
That's all that was attempted today. Gear shift lever is tough yet movable. I'm going to put my nose in the manual and see if I catch anything that I may have missed. Feel free to suggest ideas to try if you've been down this road. Thx again
Michael
Is the cable for the shift lever adjusted properly?
If I remember from my 4106 with the Stone Bennet shifter, it's possible to manually put a V730 in reverse from the transmission itself.
Anyone with more than my very basic knowledge on this that can advise a way to test the reverse function of the transmission to isolate the problem to the shift controls or the transmission?
Sounds like the reverse planetary has stripped,above the oil pan at the output end you have 2 =1/8 inch plugs 1 for the main pressure and the other is for reverse pressure if you have good pressure on the reverse then the planetary gear is bad, the pressure setting and location are in your book,a grease gun hose with a cheap 200 psi gauge will work fine for testing
Michael -
Based on the first photo you posted, it looks like the adjusting nut for the shift linkage has just about worked it's way completely off the rod, thus not allowing the transmission to fully go into reverse.
I'd crank that nut down until there were several threads showing and then test the shifting again. It may be just that simple - at least it's worth a try.
BTW, what's the VIN of this coach? PD4905A-XXXX?
FWIW & HTH. . . ;)
RJ
The nut is just a lock (jam nut) for the threaded block the cable attaches to ,been a long time since I saw that type neutral switch
I would disconnect the shift lever at the trans end and move it manually. Move it all the way to each end and see what the bus does. F one way and R the other way. Check the pressures as well as previously explained to verify clutch damage if still won't move in R.
Hi there guys,
I had to take a small step backwards yesterday, but will have some time tomorrow to attempt some more troubleshooting. I have purchased some gauges and grease gun hose. I needed a 1/4"female to 1/8" female reduce in order to make this work. So I have purchased one to work with the only gauge that was available.(1/4"-300 psi) Once that come in I will try everything here and report back. Thanks again so much for the assistance.
Michael
P.S. I found a couple of hard copy manuals of a bus my father used to have prior to this one. If anyone would like them I can post them to you. A small contribution the back to the community. (See Attached Photos)
You're in good hands with Da Books!
Quote from: 1MOFrolla on August 15, 2022, 07:24:42 PM
P.S. I found a couple of hard copy manuals of a bus my father used to have prior to this one.
Michael -Before sending these off to another busnut, you might want to look thru them to see if there's a section on adjusting the shift linkage on the V-730 transmission, as they were use extensively in the transit buses.
FWIW & HTH. . . ;)
RJ
The "Mechanic Tips" supplemental for the V730 are easier to understand, I know you can download the "Tips" and should be able to buy the book from Ebay for less than 20 bucks, adjustments to linkage and cable are made with the transmission in reverse and you should have 3/8th of inch showing on the cable end at the shifting block,I don't know what GM calls the block but others it is called a Micro-just cable connector
v730 did NOT have a V on end of bowl
I don't know if it actually is a v730d or not, but I can confirm that the nameplate specifically says v730d. This is what I am basing all my questions off of. I did receive the manual finally, but as previously mentioned, the book doesn't really describe in detail how to set the shift cable from start to finish.
Now I have been doing other small repairs until I can get the "mechanic's tips for the v730d". If any of you have a copy or a link where to buy one, I'd appreciate it greatly. I've looked here on BCM manuals and am not sure which one contains the insert. I already have this https://www.ebay.com/itm/325183533919 (https://www.ebay.com/itm/325183533919)
Like I mentioned before. Disconnect the shift cable at the trans and move the lever manually. If the bus moves it is the shift cable if not it is a trans problem. Very simple to isolate the problem. If the trans doesn't work do the pressure tests to finalize the tests.