| Author |
Message |
Rdub
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 09, 2004 - 10:28 am: | |
Can anyone tell me (or where to find) data regarding the ring and pinion ratios (options) on the GM4905. Thanx, Rdub |
Don/TX
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 09, 2004 - 1:07 pm: | |
All the books I could ever get, showed only one ratio ever offered. The only choice was between that and the 4106. The numbers were a 4 1/8 and a 4 3/8. |
rdub
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 09, 2004 - 1:07 pm: | |
Also, I'm having a problem understanding how, as many claim, that the 4106s with the V730 conversions chug along at 75-80mph at only 2150rpm and 22.5 tires. Mathematically, that doesn't work out with a 4.125 differential. Is there something I'm missing cuz I really want to be! (missing something, that is!). Rdub |
J.L.Vickers
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 09, 2004 - 2:08 pm: | |
The GMC coach P8M4905A parts manual dated June 1976 shows a 4-3/8:1 ratio for the standard rear ratio.
But for a option the 4-1/8:1 was avaliable.
I have a Coach Final Vehicle Record for a P8M4905A
serial numbers 1647-1648 it shows that the 2 coaches came from GMC with a 4-1/8:1 ratio and a V730 automatic transmission as a option. |
Don/TX
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 09, 2004 - 5:45 pm: | |
rdub you remind me of a time back when the VW bug was first introduced to the USA. I was bumming around the local dealer, and one disgruntled buyer kept coming back time and again, asking for them to do something to make the mileage better. Finally the owner told him, you could just do what all the other owners are doing about it - LIE. |
rdub
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, November 09, 2004 - 6:48 pm: | |
Don,
I think you've hit on something..."Zen and the art of Busnut-ing". After a day of anxiously searching and refusing to accept the limitations of V-drive automatics and the rear ratios available to them, I should just sit back and accept my fate...or...maybe I could jack the rpm up to 3800 or get some 36" earthmover rear tires...or not..ummmmm-ummmmm-ummmmm. Rdub |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 6:02 am: | |
"earthmover rear tires"
Havent checked lately but the huge singles that replace the Duals in rear axles may be large enough in Dia to get more speed .
Otherwise the 12R24.5 is usually as big as you can get.
Play with Darise's computer (in the files) to get the road speed you desire at the rpm for long life , about 1800, 1900.
FAST FRED |
Frank Allen
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 11:43 am: | |
Mine has a 4:10 ratio , 22.5 tires with a 730, it goes 76, thats all i know about it all. 7.5 mpg,
Frank Allen
4106 |
Don/TX
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 3:59 pm: | |
We had determined that there was no 4:10 ratio for a 4106. Do you know the history of your differential Frank? |
Frank Allen
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 8:46 pm: | |
Don,Tx you determined wrong, there is a 4:10 and i have one and i know the history i had it put in there. i had a 4:1/8 before a butcher mech in va destroyed it. however i do not know where the 4:10 came from but could find out if anyone wants to know,because the mech that put it in is still around. .
Frank Allen
4106 |
RJ Long (Rjlong)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 9:46 pm: | |
OK, just to muddy the waters, there's not much of a difference between a 4 1/8 and a 4.10.
With a stock V-730 having 0.87:1 bevel gearsets, you get the following overall final drive ratios:
4 1/8:1 = 3.588:1
4:10 = 3.567:1
Plugging this into Daris's calculator, using the info he has for 11R22.5 tires, it ends up that the difference is less than 1/2 mph at 2100 rpm: 72.115 vs 72.539
With the OEM 4-spd, it comes up just about the same: 77.632 vs 78.125.
FWIW,
RJ
PD4106-2784
Fresno CA |
neomax
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 10:05 pm: | |
Rj: precisely what my Grumman does and let me say that running @ 2100rpm it doesn't do anywhere near 7.5mpg, more like 6 w/ a well tuned 325hp 6v92. |
Frank allen
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 11, 2004 - 1:56 am: | |
Thats about close to what i said, 76 mph, 4106, 22.5 tires, 730 trans, 7.5 mpg 8/72 engine. 4/10 rear end
Frank allen
4106 |
Frank Allen
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 11, 2004 - 1:58 am: | |
one more little note, when i had the 4/1/8 rear end and the spicer i could go better than 80 and got 10 miles to the gallon. thats the truth of it
Frank allen
4106 |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 11, 2004 - 6:09 am: | |
Sounds like your well over 2300rpm to go 76 with a 730.
That's Fire Truck RPM , no longevity guarentees.
FAST FRED |