| Author |
Message |
JJ (152.163.204.177)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 03, 2001 - 1:40 am: | |
Does anyone have first hand knowledge of a two-speed rear end in a GMC punkin' ball? Can I just change the guts in it? How about an Eaton unit,is there room between the trans. and the diff. to shoehorn it in? Do I have to change the whole axle unit? Feasible maybe, but not practical? Thanks and Cheers...JJ |
RJ Long (24.130.101.25)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 03, 2001 - 2:41 am: | |
Sorry JJ, you're out of luck on this one. :-(
The Rockwell-Standard GMC rear axle is a unique animal. If you look at your shop manual, you'll see that the pinion is not at right angles to the ring gear, like most, it's at a 63-degree angle. And the drive shaft is just long enough to keep u-joints from dying an early death due to weird operating angles. So an Eaton unit wouldn't work either.
The 4104 at one point had a 2-speed optional planetary gearset available, it mounted between the engine/transmission. The vast majority have been removed, as they were quite troublesome (in revenue service). If you could find one, it wouldn't work in the 4905, because the '04's transmission is ahead of the bevel gearset, not after like the 4905's.
Stock ratio in the 4905 was 4.375:1, the 4106/7/8 came stock with 4.125:1. I understand Geoff has put a 4.10:1 unit in his RTS, or maybe he just rounded off the numbers to a ratio that's the same as the 4106 uses. With the 0.808 angle drive calculated in, it gives the 4905 a 3.54:1 final drive ratio, and the 4106/7/8 comes in at 3.33. According to the 4108/4905 brochure I have, it specs a 100 rpm difference at 65 mph between the two - 1900 vs 1800 - with 12/22.5 tires.
There was a posting on one of the boards awhile back about somebody who put taller tires on his otherwise stock 4905. The results were ok on the flats, but the hill-climbing ability became worse, so he went back to OEM equivalent-sized tires. Something to mull over. . .
BTW, this 2-speed axle thing pops up on the boards every now and then. . .
FWIW,
RJ
PD4106-2784 |
JJ (152.163.197.77)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 03, 2001 - 11:56 pm: | |
Thanks RJ, I seem to remember it once before. Nice to know about the ratios too, no tach, but mine runs 74 mph (GPS/Fla.& KY Radar) full tilt on level ground, with 11:00/ 22.5's. I'm at about 24.5k lbs.full up in all tanks,(plus 2325# for the baby toad) so it's not struggling too hard, but occasionally a long hill needs something between the cogs I have. By the way, I don't have a placard that shows my GVWR, and cant' find it in my Manuals anywhere. You are the Guru on this sort of information. Can you give me some guidance? '72 P8M4905A/122 Thanks Again, and Cheers...JJ |
RJ Long (24.130.101.25)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 04, 2001 - 1:54 am: | |
Hmmm. . .
Can't find it right at the moment, but my (fading) memory seems to think it's 12,000 on the front, 20,000 on the drivers, and 4,000 on the optional retractable tag, giving either 32,000 or 36,000 GVWR. (Is the sticker missing off your LF windshield post - near the fresh air blower?)
Are you running 22.5s or 24.5s? Just curious, as 11:00/22.5 is smaller than OEM on the 4905 - you might be compromising safety a little if you have the smaller tire. According to my brochure, the stock tire for this model coach was 12.50R22.5 - 14 p.r. Check this link for an interesting discussion of rear axle ratios:
http://www.busconversions.com/newsboard/articles/4866.html
BTW, what do you consider a "long hill"??
Let's see - P8M4905A-122. Originally delivered by GMC to Oklahoma Transportation Company, Oklahoma City, OK, in April of 1972. It was the last of a 10 bus order, and carried fleet number O-488.
Eyelids drooping, time to close.
HTH,
RJ |
Frank Allen (64.12.101.172)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 10, 2001 - 4:33 am: | |
412 or 7/8 was standard for 4106, however there are some new 410 s out there because i have one in my 4106 to replace the old 412. i have also seen the 410 in several rts units . and i know of at least one 4905 with a 410. no big deal
Frank allen |
JJ (205.188.192.173)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, March 11, 2001 - 1:01 am: | |
Hey RJ,I apprecfiate your concern for my safety, but the 14PR Dayton 11:00X22.5 All Position Tires I put on are rated 6040 lbs. single, and 5350 lbs. dual. The coach (on certified scales) weighs 9060 lbs. front, and 15180 lbs. rear, for a gross of 24240 lbs. A long hill is on I-75 or I-77 in Ky, Tn, or WV, and is 3 to 7 miles of 5 to 9 deg. of grade. Thanks to your post to me long ago, I got in touch with John Vickers, who patched me thru to Fred Rayman. Fred kindly sent me a photo of 0-488 sitting in front of the train depot in Stillwell,OK in 1974. Ain't the net wonderful??? Again my thanks for you help and concern, and Cheers...JJ |
J.L.Vickers (209.34.1.135)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 12, 2001 - 8:08 am: | |
Hey good old F.G.Rayman came through with a photo of the old O.T.C. Buffalo.Look for a article on the "buffalo" series coaches in Private Coach Magazine. Fred is helping with the photos.
JLV |
Ol Jim, hisself (163.205.18.138)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 20, 2001 - 3:30 pm: | |
I seem to recall that GM had a 2-speed planetary gearset available in the H8H649 buses with the V730 tranny. It was mounted in front of the transmission. (I think it was between the torque converter and the V-drive).
I do not remember anything else about it, except that it acted as a 4th and 5th speed.
I almost bought a 1980 with that tranny, but the guy went bankrupt and disappeared before I had the money to buy it. |
Bill Gerrie (24.112.158.230)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 29, 2001 - 1:30 pm: | |
Jim
I never realized that GM had such a set-up as a 2 speed gearset with the V730. I have tried to find further info and draw blanks. Maybe someone else out there has info on this. It would make interesting reading. Bill |
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