Can anyone comment on replacing the nv4500 nv241hd combo with a medium duty 9 or 13 speed double or triple OD trans and divorced 205 transfer case? Just wondering how difficult it is. Specifically how to make the bellhousing, starter, clutch work and if there is enough room under the floor.

I had a gearvendors on my last 12 valve truck and I put a 4 speed browine box behind a transfer case on an '84 ford 6.9 years ago for a twin stick setup.

I'm currently down having to fix the 5th gear nut. Looks like someone else did multiple repairs and never changed the mainshaft. It's a mess and with only 85,000 miles total. A shame, really. I'm going to install new mainshaft, 5th gear, nut, and try the nut retainer.

So just thinking longer term to start getting parts for a 9 or 13 speed with 205 conversion.

 

the nut retainer is the way to go. doesnt mess up the main shaft.
ford put the cummins in their f650-850, i think you could get them with an eaton 8/10 speed or that was intersmashable, i get them confused sometimes. in the medium duty classes that eaton was sold regularly. should be easy to get the bell housing/adapter you need.

 

Ask and ye shall receive...........

Long and epic thread, but well done, and in the end, he managed to have a married TC on his.

https://www.dieseltruckresource.com/...ium+duty+trans

https://www.dieseltruckresource.com/...ium+duty+trans

 

Thanks for info Angus and Pat, much appreciated. I have read all the threads referenced in your posts. So far I have decided to install my new mainshaft, gear, nut, and retainer myself. Got the tranny out and got it opened up. I stopped after I got the mainshaft assembly out of the case. I'm going to need some bigger loc ring pliers in order to continue. So far, other than the trashed mainshaft and worn 5th gear splines the rest of the tranny looks great. The nut that backed off was the Mopar fix version that is split and uses the allen screw to pinch it tight. I was able to spin it back on by hand! Either it was not tightened or the allen bolt backed off. Hopefully, I'll have my new mainshaft parts this weekend or next week. If all goes well I might get this back on the road for about $350 in parts and a whole lot of my own labor.

As far as collecting parts for later I'm going to continue researching and will concentrate on the Fords or Freightliners as suggested that used the ISB.

 

FWIW, mine had both the fully splined mainshaft and the updated nut, still backed off. I used another updated nut and then added the nut retainer that is splined to the mainshaft and goes into the retaining nut.

So far, that puppy has worked magnificently, i tend to lug mine pretty good in 5th.

 

Yeah, I'm counting on that retainer to work. I got my mainshaft and gear in the mail yesterday. The gear is a loose slip fit on the shaft. I wish they would have made it an interference fit - heat the gear to 400 or so in an oven to put it on. Anyway, I must have read hundreds of threads by now. It seems that the retainer is fairly recent in the scheme of things and I have not found a thread reporting a failed retainer. No doubt the shaft and gear will fret and wear with the loose fit but as long as those tiny prongs on the retainer can keep the nut on then it should run. Failure mode, hopefully, will be increased fretting and wear and made obvious by eventual increased gear noise. I hope the fix will go a long time before next rebuild.

If I was going to improve the retainer system I would go for an interference fit on the full spline gear and make a nut with larger slots and a corresponding retainer with bigger or more prongs. I guess if it backs off with the retainer then it will push on the transfer case input and probably damage the transfer case. A spline design as found on the input shaft would be better than the involute splines as currently used. Involute splines are made to take pure torque not the separation forces from the gear teeth and tangential tooth load. A square cut "keyway" style spline would provide a true surface on the diameter to take the load. Maybe someone will do this eventually. So far, everyone is taking a low dollar approach. Quad 4x4 Torque King was on the right track but gave up and no longer offers a true re-design. It has to be a replacement shaft and gear designed to be assembled in a solid manner on the shaft.

And I am here to work the Cummins in its torque and efficiency range, not cater to avoiding low rpm on a poorly designed 5th gear system. I own my truck for the engine and p pump. If I have to upgrade the tranny so be it. I like a manual trans!

If I had the time and money I would have the splines on the gear plated up to make an interference fit on the shaft. I bought several nuts of different design. I have decided to use the nut with the most threads since it will hold the most loctite! Hope to have the new mainshaft in this weekend if I don't need any additional parts.

 

I put a 3 speed brownie in, and took 5th gear out. For me this works out well.

 

That's a pretty attractive way to go. Which model brownie did you use? It looks a little narrow around the fuel tank area underneath and I wonder how it would fit.

I put a 6041 Spicer 4 speed box in an '83 Ford 250 4x4 diesel 4 speed many years ago. Truck now long gone. It still ranks as one of my favorite mods of all time.

The advantages of having a synchronized main box for around town and then the un-synchronized aux box for clutchless splitting when on the open road is a great combination for sure. I still see fresh rebuilt Brownies for sale.

It's a bit of a project though with cross member fab and extra shifter and linkage.

 

I used the spicer 5831b it is close to the fuel tank but there is enough room. Driveline is off center so you have little extra from that.

 

Thanks, now I'm thinking about it!