Auxiliary Transmission Guru's ...help Needed

[macks and brockways]

I have wanted to add a auxiliary transmission to a couple of trucks in the past, but have refrained from doing so due to the high cost of the spicer 1241 and its replacement the TTC1750. The reason I want to do this is gain more on road speed/lower cruise rpms. These trucks are geared perfect for the off highway work as they sit so I am not re gearing the differentials, nor am I changing the front transmissions: so he goes my questions. I have considered trying to use a T20xx as an auxilary transmission..they are cheap, tough and have .60 overdrive. I spoke with a friend who is an engineer at Eaton and he said it would not work due to the input shaft not being designed to take the weight of a driveshaft and something else about the front bearing design. Well I spoke with another member of this board and he said he had seen it done...and spoke of using a carrier bearing right at the yoke of the front shaft to alleviate some of those concerns. Have any of you ever seen this done before? Success stories or horror stories? Think the 2050/2060 or 2070 is strong enough? What would you use for the front yoke? Think the carrier bearings rubber mount would move to much? Trans would be mounted to frame and front shaft supported at input to auxiliary by a carrier bearing?

I realize the TTC 1750 is rated at 17500FT lbs of input torque to account for the torque multiplication in the front transmissions lower gears....however if you look into one of these they don't appear to be built any "heavier" than the Mack transmission. I will also mention trucks are already 24.5 tall rubber, and as I said before not changing rear ratios or differential ratios. Thanks in advance

Got any cheap Tremec 1750's or Good Spicer 1241's laying around?

[HK Trucking]

Obviously I'm not a mechanical engineer, but my gut feeling is that with the front transmission in low gear, the torque multiplication would be too much for the 2" input shaft on the T200 series transmission to handle.

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[b61fred]

The front input bearing and shaft is designed to be supported by the collar that it slips into. I dont know if the carrier bear would be enough support for it. I suppose that it you did some machine work to make a bearing mount to support that it would work there. To figure your input torque from the other trans find out the max. torque rating of the engine and take that times your lowest gear ratio and you would have your max input torque rating.

Fred

[Rob]

I've seen this done with a Mack transmission before but it did not hold up. The input shaft was twisted off three times before the project was abandoned. An aluminum mounting block was pieced and welded through the bellhousing with a pillow block bearing mounted to support the input shaft. A coupling was then engineered to spline onto the input shaft. This seemed to work well but did not hold up to the torque multiplication of the driveline. The truck had a 4000 gallon tank and was used to pump/transfer effluent to a field from a confinement pit for hogs. Lot of weight when full, and in soft ground, the reduction gearing was needed.

Rob

[macks and brockways]

Rob, did you happen to see what series transmission they were using on the setup you are speaking about ^ ? thanks

[Rob]

Rob, did you happen to see what series transmission they were using on the setup you are speaking about ^ ? thanks

I don't know anything about being a guru but I supplied the transmission. It was a TRL-107 from a 72 R model Mack. Originally this trans was behind a 237, (ENDT-675) that I installed into another truck I had at the time. I never calculated the ratios, or really had much to do with the conversion. It was picked due to the removeable bellhousing for bearing support fabrication, and the case mounts to hold it in place so it wouldn't rock under the stress. Seemed to work alright. The truck was a 78 R-686 with a ENDT-676 engine and a two stick six speed that did not have the deep reduction first gear.

Rob

[b61mack]

The front input bearing and shaft is designed to be supported by the collar that it slips into. I dont know if the carrier bear would be enough support for it. I suppose that it you did some machine work to make a bearing mount to support that it would work there. To figure your input torque from the other trans find out the max. torque rating of the engine and take that times your lowest gear ratio and you would have your max input torque rating.

Fred

Hi Morgan, i have been thinking about calling you. i was at a swapmeet in Indy the last couple months a guy had a few new sets of the old cab lights (KD517) and some others with glass lens i was wandering if you need a set i would pickup a set if you wanted some. Ron

[theakerstwo]

If you go to the eaton website you may get some ideals about how to do this. First place i dont think it is a good ideal or think it could work. But you can use a eaton trans and eaton did make the parts to make a trans like a 10 speed or 13 speed into a midship mount. That required aspecial input shaft and brg retainer that a yoke can be installed on it and the front brg was a double roller brg keeping the input shaft in line with the trans.On your ideal i dont know how you was planning on connecting a yoke to the input shaft or am i not understanding your question? The midship mount that eaton had was for mounting a trans back in the frame with a drive sfaft between the trans and the clutch for what ever reason. I did see years a go a freind of mine build a motor home out of some different trucks and he used a ford engine and 4 speed trans and he put a another 4 speed turned around backwards behind the first trans. He had the input shaft re machined to take a yoke and also built a double roll brging and mounded to the trans case and supported the trans input shaft which is now out put shaft. But this was of no use in the end. He had 3 more over drive gears and non that he could use because the over drive was to large.