I broke my transfer case - BW1350M

[Spott]

My speedometer stopped working about 3 months ago; a minimal amount of investigation showed that the teeth had worn off of the speedometer drive gear inside my BW1350 TCase. The driven gear didn't look too shiny, either.

I pulled the rear driveshaft, bought a 30mm socket, pulled the mounting plate off the rear output shaft, popped the oil seal out, and confirmed that, yes, my speedo drive gear was toast, and that I had a red (6 tooth) gear, which is too slow for my stock-sized tires anyways. So I put it all back together and started looking for parts.

There's a great transmission supply warehouse here in town, and they were able to order in a "good used" 7-tooth gear for me. These gears, either the 6- or 7-tooth, are apparently rare and valuable anymore. So today I went and picked up the gear (which is in beautiful shape), and a 17-tooth driven gear as well, and this evening I attacked the problem.

All proceeded well, until I went to put the 30mm nut back on the rear output shaft, to hold the driveshaft mounting plate on. The factory service manual said it needed 150-180 ft-lbs of torque, so I grabbed hold of my 15" breaker bar and torqued it down a good grunt-and-a-half. There was a funny "ping" sound, and the nut got really easy to turn for a moment...then it came right off. I had broken the threaded end off of the rear output shaft.

Now, I'm not a huge guy...6'4", 210 lbs, an active cyclist, and I might be able to do one chin-up on the bar. Lying on my back under the truck, there's no way I put more than 200 ft-lbs of torque on that nut, right? To get it off the first time, I had to grab the frame rail and push against the end of the breaker bar with my foot. D'ya think that sometime in the past, somebody overtightened it with an impact wrench, and weakened the threaded shaft?

I intended to rebuild my transfer case soon, but I was hoping to wait a month or two, and arrange to have a full day off to work on it. Now I'm stuck. I'm relying on my carrier bearing to hold the driveshaft mounting plate onto the splines of the rear output shaft, so I don't dare drive very far or very hard. I might be able to get a "good used" rear output shaft at the transmission warehouse (the parts guy mentioned a "box full of misc 1350 parts" lying around), but I'm not sure my budget will support this latest disaster.

Also, what are the chances I can rebuild my transfer case (or at least replace the rear output shaft), using the '88 ford factory service manual, in 4 hours or less, so I can get to work on Friday? Or should I plan to ride my bicycle to work? It's only 12 or 13 miles, but an hour on the bike riding home, is an hour I can't work on fixing this problem.

Comments or suggestions are greatly appreciated,

Spott

 

[4x4junkie]

Been awhile since I had the rear section of a t-case apart, though I seem to recall the output shaft is pretty much right there after you've pulled the rear cover off. I'd say 4 hours is plenty of time to swap it.

 

[snoranger]

Remove the rear driveshaft. Put it in 4wd. Drive it to work "front wheel drive". Fix it on the weekend when you have more time.

 

[Spott]

Remove the rear driveshaft. Put it in 4wd. Drive it to work "front wheel drive". Fix it on the weekend when you have more time.

I would have, except for one little detail...without the driveshaft there, there's nothing to keep the driveshaft mounting plate from falling off the end of the rear output shaft, and then all the oil splashes out.

It worked OK for one day, using the carrier bearing to keep it in place.

Spott

 

[Spott]

Well, the transmission shop didn't have a rear output shaft in stock, in fact, the parts guy said "Well, it's the kind of thing that just doesn't break, so we haven't ever sold any."

They found a good used shaft at their other shop across the state (apparently they hang on to them so they can use them to rebuild t-cases) and it will be here tomorrow before lunch.

I got a head-start on the job tonight, it took me an hour and a half to get the transfer case off of the truck, and half an hour to open it up and take the (broken) rear output shaft out. Tomorrow I'll ride my bicycle to work and get the parts (including a seal kit) and then tomorrow evening I'll rebuild the t-case.

Haven't wrecked anything else either, yet.

Spott

 

[snoranger]

I've seen it happen before.

I snapped the rear output shaft off at the end of the splines. The driveshaft fell to the ground, dug in, and lifted the back of the truck off the ground.
Good thing I was only doing 25 MPH!

 

[Spott]

Well, this just keeps getting better. I went and picked up the replacement rear output shaft, and a seal kit, and 2 quarts of oil and a tube of silicone gasket material. I stuffed all this in my backpack, and bicycled home with about 40 lbs on my back.

I went out to the garage to start reassembling my transfer case, and started by trying to put the oil pump assembly back on the output shaft. I tried to put the two little sweeper pins in their holes, in the sides of the output shaft, and they don't fit. They're too big. The holes in the old shaft were about 3/8", and the holes in the replacement shaft are about 11/32". The shaft, and the pins, are unbelievably hard (I have a wrecked 23/64 drill bit to prove it) and the transmission shops are all closed tomorrow.

All I can do at this point, is scrape the old RTV off the case, and hope for good weather tomorrow.

Spott

 

[4x4junkie]

Can you get the oil pump that was with that shaft?

 

[Spott]

Can you get the oil pump that was with that shaft?

That would, of course, be the ideal solution, but the shaft was shipped in from their other shop, on the other side of the state, and I haven't talked with the guys over there. It's a used shaft as well, and there's a good chance it was separated from the corresponding pump years ago.

On Monday, I will certainly inquire further. There are replacement oil pump kits available as well, and one of them may fit.

Spott

 

[Spott]

Finally got it figured out! Went back to the transmission shop, and they called the other shop that shipped the part, and found out the shaft was from a BW 1354, which uses a completely different style of oil pump. Aside from that, it's identical to the 1350 shaft.

I bought the oil pump for the 1354, and a chainsaw sharpening grindstone for my dremel. I ground out the old (sheared-off) pin from the shaft, pressed a new pin in, and reassembled the transfer case. The triangular tab on the 1354 oil pump fits into a space next to the slot for the 1350 oil pump, but there's no hassle there.

By the way, Loctite RTV 598 black silicone gasket material comes in a really cool dispenser can, kinda like a can of easy-cheese. You just hold the lever, and it squirts itself out in a nice bead. Kinda spendy though.

Got all the seals replaced, hoisted it back up onto the transmission tailshaft, and hooked everything back up. An old turkey baster (a bulb baster) is the perfect tool for refilling the case with AFT oil.

Took it for a spin around the block, and my speedometer is reading a steady 2.5mph high, at all speeds. I need to adjust the zero of the needle back to where it should be, and it'll be spot-on.

Spott