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FAST FRED (63.208.83.224)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 17, 2002 - 8:45 am: | |
Am posting some info I recieved from an engineer at TCM, who was kind enough to share his opinion of bringing a GM Coach powerplant up about 75 years.He was less than enthusiastic, as the 4 strokes vibrate more than out 2 strokes .
Toured your web site , and thought you would have the background to
answer a problem.
I have a 1964 GM 4106 , standard as delivered .
I have been told that some of the RTS are very close to the old GM , in terms of engine mounting etc.
The engine in my GM has only 90,000 miles , but eventually the time will come, even when only used as RV.
If you have an 8V71 in it, and it has been well-maintained, you should
have a very long time yet before it requires a major or replacement.
I would like to purchase a transit "donor" coach and end up with a 4
stroke engine , the newer tranny , rear axle with big breaks , and
hopefully be able to use even the front axle with sharper steering axle.
Believe me, you don't want a big 4-stroke engine. Vibration is a real
problem with any 4-stroke.
Do you know which 4 strokes were stuck in late model transits , how the
service was, and which would be best to search for as a donor?
As for finding a suitable donor, to get all the above, there's about a
four-year window for 4-strokes and the better brakes, since in 1998, we
went to 14-1/2" s-cams when ABS became required. Any 1997 or prior RTS
will have 15-1/8" wedge brakes. As for maintenance, you'd be able to
tell when the bus is at the end of its transit lifetime how well it has
been maintained. (!)
As for finding them, every larger transit agency has a bus procurement
officer, and that person can tell you if they are replacing buses, when,
and if they plan to auction the end-of-life buses or scrap them.
I would prefer a stick shift , but have been informed that its out of the question.
No RTS was ever equipped from the factory with a manual transmission.
V730 or V731 automatics only.
So do you know anything about the service history of the auto trannies?
Single largest failure point is the PTO drive. Two best things you can
do to extend service life are to install a ZF oil cooler and to increase
the change interval for fluid and filter from 30,000 miles to 12,000.
2.
Thank you very much for all the information.
I realize its sometimes a pain to answer questions from a perfect
stranger, but I will impose with only one more.
I realize any 4 stroke will be a shaker , compared to the 8V 71 , but given the choice of engine + trannies installed in RTS , which
combo would be your preference?
In terms of ease of operation (not necessarily maintenance costs), a
V731 trans is probably superior to the V730 or the earlier VH and UH
transmissions, because of electronic shifting and fuel economy, due to
electrical lockup at the top end. But, truth is, we've had lots of
problems with ancillary parts for _all_ 4-strokes, because of vibration.
And, our costs have gone up by the forced changeover to 4-strokes. The
DDC Series 50 really thrashes around on the mounts, and transmits a lot
of vibration through the structure, which eventually causes cracks in
embarrassing places, and nagging complaints from drivers due to exterior
mirror shake. The situation is not much different with the big Cummins
engines, such as the M-11s or L10s.
Downside of the V731 is the quill for the PTO when used for compressor
drive. That's the significant weak point in the transmission. And,
Allison will not warrant the PTO if it drives an a/c compressor without
drive dampening on the compressor clutch input.
Of all the 4-stroke installations we've done, I would say, at present,
the least problems with vibration have been with the C8.3 ISC Cummins
engine mated to a 5HP590 ZF, because it's a smaller package overall.
But, I have to say that such a modification, with new parts, is probably
in the $75-85K range, including suitable cradle, radiator, charge-air
cooling piping, harnesses, etc. And, even with that, we've still had
serious vibration problems with the 8.3. Not structural, but with a/c
parts produced by Thermo-King. That problem has been resolved, but it
did relate to an up-and-down vibration component.
But, not all people are in favor of the 8.3, because it doesn't have the
longevity of some DDC engines. In transit service, it's a 300-350K mile
engine.
For your purposes, you could spend a lot less money to keep the 8V-71
going, and with fewer problems. I know there's a natural urge to upgrade
to the latest and greatest, but I think that very few recreational
owners understand the huge costs required for upgrades, and that much of
those costs mostly relate to changes in emissions standards required of
transit fleets these days, and to the fact that we're living with
increased pricing due to lower volume. In its heyday, GM was producing,
between New Looks and RTSs, sixteen buses a day. We're down to producing
about one a day. That has an effect on prices from the engine and
transmission manufacturers which has ripples throughout the industry.
A very good alternative to going to 4-stroke, though, would be to
contact one of the larger rebuilders, such as Jimmy Diesel in Chicago,
and asking them about a rebuilt 6V92 with DDEC I or II, or if they've
done 8V71 conversions to DDEC controls. You might also ask Blitz in
Chicago if they have some alternatives available to a mechanical 8V71.
Hope this PRO's info will help with folks deciding on a repower for the 21'st century
FAST FRED |
Dennis (24.118.102.10)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 17, 2002 - 9:00 am: | |
Thanks for that Fred, very interesting. |
Greg Roberts (Gregeagle20) (66.7.134.190)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 17, 2002 - 4:33 pm: | |
certainly gives me confidence in my DDEC II 6V92 Allison ATEC HTB748 package. Thanks Fred |
Tim Bookmiller (205.188.209.11)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, October 29, 2002 - 9:03 pm: | |
Very interesting reading --thanks Fred for the info |
Buswarrior (Buswarrior) (64.229.213.188)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 13, 2002 - 10:16 pm: | |
For those who aspire to greatness, take note of the excellent research strategy employed by our good friend, Fast Fred.
Why not go to the folks who have transitioned a V-drive coach from two stroke to four stroke?
The man is simply brilliant in his simplicity.
Never mind gossip, dreams, theories, excessive cash for experiments and armchair quarterbacking, find the source, humble yourself and ask the questions.
And then share with the greater community your success and your failure in research.
Thanks FF, for setting a fine example.
Hmmm, I wonder how big an injector that an early DDEC will run without smoke in my 8V71.......
happy coaching!
buswarrior |
RJ Long (Rjlong) (24.127.74.29)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 14, 2002 - 12:43 pm: | |
Excellent point, Buswarrior!
When did you say you were contacting DDA regarding your injector question????
LOL 8^)
RJ
PD4106-2784
Fresno CA |
Buswarrior (Buswarrior) (64.229.212.43)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, November 16, 2002 - 10:32 pm: | |
Only mumbling, RJ, only mumbling....
No real motivation to find out, only mild academic interest.
I am quite satisfied with the stock performance of my MC8's 8V71 at it's 285HP or whatever is back there.
What others think they are making up in time with their beefed up power plants, I'll win back in spades with my bus driver's bladder, and lower fuel costs.
Oops, sorry, in polite english: the turtle won the race while the rabbit was at the rest stop.
happy coaching!
buswarrior |
charles seaton (205.183.220.250)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 18, 2002 - 4:20 pm: | |
For Fast Fred;
I saw an early model RTS recently that was delivered new with a straight 6-71. Never knew such a beast existed, but they do. |
Geoff (Geoff) (64.1.0.109)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 18, 2002 - 8:24 pm: | |
"I saw an early model RTS recently that was delivered new with a straight 6-71. Never knew such a beast
existed, but they do."
Well, you should of had your camera because I don't believe it! 6V71, 8V71, or 6V92 is all that I have ever heard of in the GMC RTS's.
--Geoff
'82 RTS CA |
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