Need help in Nashville, Tn. Update

Bob & Tracey · October 14, 2015, 09:37:53 AM

Clifford and Scott,

I have been advised that if this bus has been sitting for more than two years that I should expect the bearings to be rusty and that would be a bad thing. Opinions please...

luvrbus · October 14, 2015, 10:39:21 AM

They do rust but I have no idea how long the time frame is it all depends on how clean the oil was when parked and the weather in that location here in the desert they set for 20 years without any rust with clean oil

eagle19952 · October 14, 2015, 10:43:35 AM

Quote from: luvrbus on October 14, 2015, 10:39:21 AM
They do rust but I have no idea how long the time frame is it all depends on how clean the oil was when parked and the weather in that location here in the desert they set for 20 years without any rust with clean oil

wouldn't they know before they shipped it ?

luvrbus · October 14, 2015, 10:48:50 AM

You could pull 1 cap and tell in hurry that oil film will last a long time unless it had water when parked,some you buy from shops are rebuilt and set on a shelf for years with no rust

Scott Crosby · October 14, 2015, 01:56:11 PM

People say that about wheel bearings too but it's not as common as they claim.... Rear end is much more likely to not have water in it to cause rust. many times they get moved around on people property every once and a while too and that's good for a new coat of oil. Even if it is bad then you just get some bearings, the hard part to get is the ring and pinion not the bearings. I'd plan on ordering the seal for sure. You don't want to have that thing out and not put a new seal in it.

What's exactly wrong with yours?

luvrbus · October 14, 2015, 02:35:49 PM

If the price is right I would roll the dice if the seller says no rust JMO,you don't even want to go there replacing the 5 bearings,they are hard to find and not a easy task setting one up,it probably would cost you 1500 + bucks to replace the bearings and thrust washers with labor .
If you have doubts check with Pro Gear in Orlando Fl they may have a rebuilt unit on their shelf, I know they stocked the ring gear and pinion a few years ago.Ed at Jefferson Bus in OKC OK could have one ready to go also, he will probably want 4 grand for a exchange though

Bob & Tracey · October 14, 2015, 02:56:49 PM

Thanks guys,

Scott, could you find out what kind of money your guy would want if his looks good?

Bob & Tracey · October 15, 2015, 12:30:42 PM

Scott,

We have a differential on its way, please let your guy know that we will not need his.

Thank you for all your help,
Bob

RJ · October 15, 2015, 07:15:21 PM

Bob & Tracey -

Just some info/education for you:

The 35-foot manual gearbox 41XX series GM parlor coaches were designed around tires that turn 495 revs per mile. Those buses all came with a 4.125:1 rear axle ratio as stock. The 4104s with the optional and problematic Hydra-Shift 8-speed had a 3.55:1 rear axle ratio, which is very, very rare.

The manual gearbox 49XX series 40-foot GMs came with a 4.375:1 rear axle, slightly lower to compensate for the heavier coach. These run about 100 rpm faster at the same road speed as the 35-foot models.

The manual gearbox in both the 35 and 40 foot bus has a bevel gear ratio of 0.808:1. When you do the math, the OVERALL rear axle ratio becomes:

35-foot: (4.125 x 0.808) = 3.333:1
40-foot: (4.375 x 0.808) = 3.535:1

Now, when you change over to a V-730, your OVERALL rear axle ratio changes, because the automatic has a different, lower, bevel gear ratio: 0.875:1. Doing this math yields the following numbers:

35-foot: (4.125 x 0.875) = 3.609:1
40-foot: (4.375 x 0.875) = 3.828:1**

As you can see, the automatic ends up with a lower overall rear axle ratio, which means more engine rpm at the same road speed.

The only way that I know of to compensate for this is to find tires that turn LESS than 495 revs per mile, which often means going to the 11R24.5 size. Tires that are in the 470 rev/mi range come the closest to matching the original overall ratio of the manual gearbox 35-footers if you have a V-730.

I know this doesn't help solve your problem, but thought you'd find the info helpful - especially next time you're shopping for tires.

FWIW & HTH. . .

** There is an exception to this: If the 40-foot 49XX coach was ordered NEW from the factory with a V-730 ('76 or later), then GM slipped in the 4.125:1 axle to compensate for the lower-geared automatic. They also came with 12R22.5 tires as stock.

luvrbus · October 16, 2015, 06:46:58 AM

All V730 are .875 final at the drive shaft connection,so what rear gear is he running turning 2100 at 60 mph ?

RJ · October 16, 2015, 07:48:39 AM

Quote from: luvrbus on October 16, 2015, 06:46:58 AM
All V730 are .875 final at the drive shaft connection, so what rear gear is he running turning 2100 at 60 mph?

Probably 11R22.5 tires.

Bob & Tracey · October 16, 2015, 09:36:07 AM

Tires are 12R22.5.

luvrbus · October 16, 2015, 10:01:21 AM

So can they determined what ratio you had. 2100@60 mph just doesn't sound right to me with a V730 and 4:10 gears

Bob & Tracey · October 16, 2015, 11:10:16 AM

Tach could be off???

RJ · October 16, 2015, 11:27:05 AM

Quote from: luvrbus on October 16, 2015, 10:01:21 AM
So can they determine what ratio you had? 2100@60 mph just doesn't sound right to me with a V730 and 4:10 gears.

Doesn't sound right to me either, Clifford.

I looked up the tire revs/mile specs for Michelin, Goodyear, Firestone, Bridgestone and Yokohama 12R22.5 tires, and came out with an average of 485 revs/mile for that tire size.

Plugging it into the formula (tire revs/mile x overall rear axle ratio = engine rpm @ 60mph) gives the following:

485 x 3.609 = 1750 rpm (4.125:1 axle w/ 0.875 bevel V730)

485 x 3.828 = 1857 rpm (4.375:1 axle w/ 0.875 bevel V730)

Now if you divide 2100 rpm by 485 revs/mile, that gives an overall rear axle ratio of 4.329, which, when divided by the 0.875 bevel gear ratio, gives you a ring & pinion of 4.947:1, which is awfully close to the Fishbowl's common 5.03:1 rear end.

If you plug the Fish's rear axle ratio into the formula, you get 485 x (5.03 x 0.875) = 2134 rpm, which is close to what Bob's reporting.

(TomC's AMC transit has a 4.56:1 gearset, which gives him (485 x [4.56 x 0.875]) = 1935 rpm @ 60 mph, also close to Bob's.)

So, if Bob's speedo and tach are accurate, it's possible that somebody swapped a transit pumpkin into the 4106 housing. . . And if Bob gets a good stock 4106/7/8 pumpkin, he's going to be happy, because his rpm will go down at 60, which also means, theoretically, that his fuel mileage should go up slightly.

Perhaps Bob can check the numbers stamped on the end of the pinion shaft to see what he currently has. It should say 8/33 or 8-33, 833 or 338, some combination thereof. With those numbers, we can better determine what's going on.

Clear as mud??

FWIW & HTH. . .

(PS: Plugging the OEM tire size the 4106 powertrain was designed around (495) into the manual gearbox bevel ratio results in (495 x [4.125 x 0.808]) = 1649.8 rpm, which is, with rounding, exactly as published in the 4106 sales literature: 1650 rpm @ 60 mph. Whaddayaknow?!?!?)