| Author | Message | ||
| Glenn Williams (Glenn)
Registered Member Username: Glenn Post Number: 61 Registered: 6-2006 Posted From: 216.163.57.94 Rating: N/A |
I'd like to find out the best combination of these parts. In looking at 2 gmc 4905's, both with 8v71's one with a spicer the other (let's assume) a vs2-8, is there a fuel advantage in using the ring and pinion from the stick bus on the vs2-8? I understand the loss of power on hills. Being a flatlander in Michigan, it is a loss I can accept. I'm young, but that clutch is a knee killer! I'd also like my wife to be able to drive - most likeley in an emergency only! She thinks a full size van is too big! | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 56 Registered: 1-2005 Posted From: 208.66.38.115 Rating: N/A |
Glenn, I converted a 4106 to VS2-8 and found the rear end gears way too high (4.125-1) I changed the rear gears to 5.55:1 and dropped it right in the usable range. So now I have a 3 speed, all usable for all purposes. (will top out at 85 MPH) >>>Dan 4106-1261 | ||
| Jerry Liebler (Jerry_liebler)
Registered Member Username: Jerry_liebler Post Number: 272 Registered: 3-2005 Posted From: 67.141.34.223 Rating: N/A |
Glenn, The 4905s came with either a 4.375 or a 4.444 rear end no matter what transmission, most were the 4.375. While the 4106, 4107& 4108 all used a 4.125 rear axle. Some of the VS2-8s have effectively a .6 ratio in high gear. There was another vs2-8 that had an effective .8275 high gear. The v730 is an effective high gear of .875. The Spicer manual transmission is .808. So if it's a factory VS2-8 installation it will be the .8275 set up, just a tad lower top speed than the Spicer. The transmission that Dan used came from a transit bus. Regards Jerry 4107 1120 | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1280 Registered: 12-2000 Posted From: 67.181.189.94 Rating: |
Glenn - The clutch on the GMCs should NOT be a knee-killer. That's a dead giveaway that the clutch is not adjusted properly, and/or the springs on the "mousetrap" have lost their tension or are missing, have seen both. When adjusted properly, GMC clutch effort is somewhere between an original VW Beetle and a Chevy/Ford/Dodge pick-up's. The stick shift 4905 will get better fuel mileage than the automatic, period. Difference will be 1 -2 mpg on the highway, depending on which auto is installed, the VS2 or V-730, worse around town. Regardless, a moot point when you're talking about a vehicle that has the aerodynamics of a brick! Don't assume that the 4905 has a VS2, you know what happens when we assume things! Easiest way to check is the shift lever or switch (if it's got an electric Stone Bennett shifter). If it's a VS-series, there will be three positions: F - N - R If it's a V-730, it will be: R - N - D - 2 - 1 If you really want an automatic coach, then stick to looking for one already equipped, rather than trying to cobble something together from a mish-mash of parts - far less headaches! FWIW & HTH. . .  | ||
| Steveggt (Steveggt)
Registered Member Username: Steveggt Post Number: 25 Registered: 12-2006 Posted From: 71.116.72.37 Rating: N/A |
Hi Glenn! You've received a lot of good information here! I'll try to add my 2-bits' worth and hopefully not confuse you any more. Let's start with the VS2-8. Standard "transit" came with a 6-1/7 rear end. Your shifts would occur at approximately 28 and 45 with a top speed of around 72. I belive the overall ratio in top gear was around 0.60. An optional "transit" had the same rear-end ratio, but the overall ratio was around 0.72. Your shifts were around 25 and 37 with a top speed of 57. San Francisco Muni buses had this lower arrangement for hill-climbing purposes. Interestingly, if you took a "Muni" VS2-8 and coupled it with a 5-1/6 differential, you'd get similar performance to the standard setup (72 top speed). Since you have 4905's, standard rear-end is 4-3/8. Needless to say, with a "standard" VS-2, you'd fly down the highway (I calculated about 95) but have no power at the lower end, especially on hills. A "Muni" tranny setup will help a bit, but you'll still be moving pretty fast (about 80). As an aside, most RTS buses came with the V730 and "standard" rear-end of 4-5/7...top speed was around 64. I know of a lot of motorhomers who've removed the manual 4-speed Spicer in favor of the automatic V730 and are quite pleased with the performance. This might be the simplest option for you, especially since your wife might be driving. As indicated in previous posts, the 35' buses came with the 4-1/8...you'll find that a lot of RTS converters are looking for this rear-end because it'll give them around 70 at the top end. One big thing to consider is the availability of parts and mechanics who are familiar with these types of transmissions. VS-2 parts and mechanics are unfortunately becoming fewer -n- far between. There are more 730 parts and knowledgeable mechanics available. Personally, I love the uniqueness of the VS-2's operating characteristics, but from a practicality and driveability perspective, I feel the 730 is a better choice...you have more control over the tranny's behavior. With regards to fuel economy, you'll almost always get better mileage with the manual transmission...just like your car. However, if you'll be on the freeways a lot, both the VS-2 and the 730 are "locked up" at those speeds, so the difference (especially on a longer road trip) will not be that great. Hope this helps! - Steve | ||
| Frank Allen (Frank66)
Registered Member Username: Frank66 Post Number: 56 Registered: 10-2005 Posted From: 64.12.117.73 Rating: N/A |
dont know about the vs2, but the 730 will reduce top speed , the engine will run hotter, and fuel mpg hiway driving will be reduced by at least 2. i put a 730 in my bus but i wish i had left the spicer in it, thought my wife would drive if i had automatic, she did drive about 50 miles, thats it. |
