FirstEliminator Posted July 17, 2016 Share Posted July 17, 2016 Hey guys, Here is an idea I'm beginning to ponder, but not finding many answers on the internet for specs to help me determine what I can go with. The vehicle is a 1957 GM 4104 bus----like an old Greyhound. It has a 6-71 inline and a 4 speed Spicer. I like the manual, but 1st gear is so high. It's nearly impossible to start on a hill. In a bus forum I belong to I heard some later bus transmissions in 70's were 5 and 6 speed. But, I don't know what is entailed in swapping one of those in place of the 4. I was thinking about what could be done then realized my 71 Brockway 361 is a 5 speed with a Spicer 8341 air shifted 4 speed aux-box. Here are some of the questions I am trying to find answers to: Through my searching I've noticed there are both 3 and 4 speed auxiliary boxes. There is no need to go with a 4 in the bus. Plus, space for adding an aux-box is going to be tight. Not sure if space is an insurmountable problem. So, I am hoping the 3 speed is short enough to fit with enough driveshaft length left to accommodate the suspension travel. What are the torque capacities of the Spicer 6231, 7231 and 8031? I did find the the specs of the 5831 are 275 torque and 150 hp. The 8031 might be a bit big for the bus. Which makes it look like either the 6231 or 7231 might be appropriately sized. Realizing that part of Spicer's model number denotes torque capacity, I would think a 7231 would be best suited to the 7141 trans that is in the bus. Are either of the 6231 or 7231 available as an air shifted unit or can air shifting be adapted to a manual unit? Two stick trucks are awesome. Although, mounting the air switch and running air lines would be way easier than figuring out how to fabricate linkage to go back 35 feet. What are the lengths of these? The drive shaft in the bus isn't very long and I am not sure how much room there actually is. As for ratios, I would prefer something with an underdrive of 2.00:1. I have seen the UD listed in the 5831 specs with 2.35, 2.00 and 1.27 available. Since I am only using this UD to get the bus moving and don't plan to split every gear, the small ratio drop probably wouldn't be worth the effort. Plus, it looks like I can overdrive one gear down in the trans to split for climbing a hill. Any recommendations or advice would be great. thanks, Mark Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted July 17, 2016 Share Posted July 17, 2016 would a two speed diff be a easier option would give you a lot lower first gear run wires up to the gear stick tail shaft most likely wont have to be changed and parts are easy to get Aux trans are getting hard for parts these days and every one wants what you are chasing, under, direct and over drive and they are pretty much rare as hens teeth out here now Paul 1 Quote Link to comment Share on other sites More sharing options...
Brian Blaylock Posted July 18, 2016 Share Posted July 18, 2016 Don't have many answers for your questions but the 8031 8035 and 8341 all have the same case just different parts inside Quote Link to comment Share on other sites More sharing options...
Brian Blaylock Posted July 18, 2016 Share Posted July 18, 2016 also might want to consider an air shift 4x4 married box Quote Link to comment Share on other sites More sharing options...
FirstEliminator Posted July 18, 2016 Author Share Posted July 18, 2016 Looking at the available space, a married box might be the only way to go. Quote Link to comment Share on other sites More sharing options...
Freightrain Posted July 18, 2016 Share Posted July 18, 2016 Mark.............PICS OR YOU DON'T ACTUALLY OWN IT!! Come on, you know the rules!!!!! Very cool project. Just another one of my "wish lists". There was a 50's GMC for sale locally, 671/4spd. I bet they were really hard to get moving on any kind of grade and slow to accelerate with only 4 gears. Still cool looking. I have a 6041 4spd in my truck. I think it is only rated at like 200 hp. I can get you some basic dimensions. I know it has 2.19 low hole in it. But you can't shift out of it while moving basically(it is only progessive in 3 gears). Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
BillyT Posted July 19, 2016 Share Posted July 19, 2016 Mechanic mechanic mechanic mechanic mFirst eliminator, Gm made most of America's motor coaches (greyhound trailways,etc) for the last 60yrs,they were built to run70+ mph so they could maintain their schedule.that + the fact that most bus terminals are on the level accounts for the high gears! The early ones like yours were mostly 671's the later ones 8v71's.Perhaps you could go to your local bus maintenance facility and find an old mechanic who worked on the old buses and see if they retrofitted any 6 speeds or if he thinks it would bolt up! Old mechanics like old truckers like to b.s.! Like someone said an air shifted 4by4 might be good.I know a 20 speed air shift Spicer can be bolted to a 671 because I drove one,but that is more gears than you need on a relatively lightweight bus! I don't know what h.p. your 671 is but they are fairly easy to "turn up" bigger injectors etc. I'm not 100 percent sure but I think that Jimmy I drove had a turbo as well as the 671blower.It was one of the last 2 cycle Detroit's made and they were trying to improve fuel economy.Maybe if you got a few more "ponies"the present tranny would be tolerable. oh by the way I didn't write mechanic four times! The computer did that on it's own. Quote Link to comment Share on other sites More sharing options...
BC Mack Posted July 20, 2016 Share Posted July 20, 2016 you're going to have to go a few rounds with the busnuts.... I have a PD4501 Scenicruiser with a T-Drive, 8V71, 4 speed and 3.7 diff.. first gear goes from 0 to 18mph..!!! not many options for a direct replacement as you have a transverse engine/trans with a bevel drive. I have seen one conversion to a 6V92 and Allison 730 off a later fishbowl Transit, took some work and ended up only as useful as a 4106. not many 4104's can be considered a hotrod or hillclimber..!!!! simply moving up to a 4106 or MC5 seems to help some owners, as does putting the bus on a diet.... amazing what the interior stuff weighs. I had my clutch rebuilt with friction material that allowed it to slip and not heat up, shorter life yes, but I have to slip it up to 10mph even empty (31,000lb) so a hill start is no fun.... and reverse is 2nd gear. Is your clutch wet or dry?? try this forum..... http://busgreasemonkey.com/ you have to send Scott an intro to join but they may have a solution for you but generally these mods cost more than the coach is worth... that will be the math you need to do.... you will not be the first 4104 driver looking for more power and gears. good luck BC Mack Quote Link to comment Share on other sites More sharing options...
FirstEliminator Posted July 22, 2016 Author Share Posted July 22, 2016 Hey Larry!!! Surprised I don't have any pictures than the seller's for sale pictures that I saved. My Brockway has an air shifted P-8341-D which has a 2.40:1 Lo-Lo. I've had no problems shifting it from Lo-Lo to UD. Worst case scenario is if it won't shift out of 1st--Lo-Lo, I can shift the main up to 4th while in Lo-Lo to crest a hill. The 1st/OD ratio is between 2nd and 3rd. Either way, there'd be 16 speeds to choose from. Hi BC, I was a member of the busgreasemonkey forum. I didn't post enough and I think I lost access. I already had several threads running on busnut. I have a few ideas on making this work, but really need to get the bus and a Spicer 7014 in hand to form a plan. I found a few 7014's that were cheap enough to take a gamble on seeing if it fits. High first gear seems to be a common complaint. A 4 speed aux-box would be perfect for this application. It would be great for reversing too. I'm not too worried about putting in more work than the bus is worth. It's a hobby, so funneling away money regardless of resale price is an accepted fact. Adding this aux-box is a desire that is turning into a mission. Time will tell. thanks, Mark 1 Quote Link to comment Share on other sites More sharing options...
m16ty Posted July 25, 2016 Share Posted July 25, 2016 On 7/17/2016 at 4:26 AM, mrsmackpaul said: would a two speed diff be a easier option would give you a lot lower first gear run wires up to the gear stick tail shaft most likely wont have to be changed and parts are easy to get Aux trans are getting hard for parts these days and every one wants what you are chasing, under, direct and over drive and they are pretty much rare as hens teeth out here now Paul I tend to think this may be the best option. Swapping out to a 2-speed rear should be a lot easier and cheaper than trying to shoehorn a auxiliary box in there. A 2-speed rear should be pretty easy to locate fairly cheap. Quote Link to comment Share on other sites More sharing options...
BC Mack Posted July 26, 2016 Share Posted July 26, 2016 21 hours ago, m16ty said: I tend to think this may be the best option. Swapping out to a 2-speed rear should be a lot easier and cheaper than trying to shoehorn a auxiliary box in there. A 2-speed rear should be pretty easy to locate fairly cheap. the driveline of a GM coach 4104/4106 or Transit bus (Fishbowl) is a lot different to a truck... the engine be it straight 6 or V8 is transverse mounted, coupled to a transmission via a 90 degree turn which on the output is further deflected about 45 degrees... the driveline is diagonal from right rear of engine bay through a bulkhead to the diff which is located on the far left of the axle banjo, up against the brakes, the input to the diff also has a 45 degree turn... all this is mounted on a cradle with muffler et al, and is supported by struts to the rear roof structure and in the forward lower end of the cradle at the intermediate bulkhead for the axle radius rods. the whole body is monocoque... so...... the gearing issues have been flogged to death on the bus forums and I'm sure this idea for an aux box is actually a good idea, but the engineering has never been explored too deeply as the bus hobby is only used to "bus parts"... it will be a tight fit. I stole a few photos just for educational purposes... it shows a removed "package" and the bulkhead with the diff showing on the left. Believe it or not, on some GM RV's with the bed at the back this is the fastest way to replace a starter on an 8V71/92..!!! to find a 2 speed diff in the correct left side position is probably impossible... more conventional layouts of T drive buses is just like a truck but 180 degrees out and can be utilised in RV conversions.. ok... bus stuff over, LOL BC Mack Quote Link to comment Share on other sites More sharing options...
Hobert62 Posted July 26, 2016 Share Posted July 26, 2016 And I thought the engine of my b67 was mashed in there. Atleast mines in a straight line. Quote Link to comment Share on other sites More sharing options...
FirstEliminator Posted July 26, 2016 Author Share Posted July 26, 2016 (edited) I've bought a Spicer 7041 and it should be here in a few days. The aux will be measured, inspected and mocked up to see how, if possibly that it cam be crammed in the bus. If not, there is a 1970 Ford C-800 parts truck with a 2 speed rear at my shop. As much as I love the old C series Fords, it might be time to take it apart. Perhaps the internals of the Eaton 2 speed rear can be made to fit in the bus 3rd member? Despite owning a transmission shop, I've never seen the inside of a 2 speed rear. GM should have made a 2 speed rear for these buses......they really need it. And yes, a high 1st gear is a very popular topic on the bus forums. No matter which method I try, there is going to be a bunch of machining to make it work. That will be half the fun. Edited July 26, 2016 by FirstEliminator thought of more 1 Quote Link to comment Share on other sites More sharing options...
BC Mack Posted July 26, 2016 Share Posted July 26, 2016 if you can make it work there could be a line-up outside your shop..!!! take care if you need to cut the bulkhead, add doublers if you do, they can buckle.... BC Mack Quote Link to comment Share on other sites More sharing options...
Mark T Posted July 27, 2016 Share Posted July 27, 2016 Ever think about smaller tires ? Quote Link to comment Share on other sites More sharing options...
FirstEliminator Posted July 31, 2016 Author Share Posted July 31, 2016 (edited) Hi BC, If I find a successful means of doing this, it probably would be something I'd try to promote for work at my shop. I'm sure there would be people interested as it has been a complaint of 4104 owners. hi Mark, Smaller tires would help a little bit. But, it'd be a direct trade off of top-end which is currently 65. Oh, the 7041 aux-box showed up on Wednesday. It's slightly smaller than the 8341 aux in my Brockway. Gosh, if it can fit at all, it's going to be tight. One thing I will have to do is measure the rise and fall of the rear suspension to determine driveshaft length before I reach the reasonable limit of u-joint angle. Do they make a double-cardan U-joint for the size of the u-joints in my bus? Drive shaft angle may be distorted in one way or another where a double-cardan may help----if they make one that size. thanks, Mark Berkshire Transmissions North Adams, Massachusetts Edited July 31, 2016 by FirstEliminator Quote Link to comment Share on other sites More sharing options...
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