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TK to M50D Tranmission Driveshaft Modifications? 86 Bronco II


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My daughter bought an cherry 86 Bronco II, but the motor leaked worse than the Valdez. My buddy donated his 91 Ranger truck. 2.9L V6 with the M50D transmission. She's been a total boss about the project, yanked two motors in two days, and turning into a motorhead. Couldn't be a more proud father.

The motor is all freshened up and we're getting ready to install. Need some help with the driveshaft mods required.

The front driveshaft out of the old TK slipped out of the transmission. The M50D had the U-joint yolk. Assumption is that we just remove the U-joint yolk and slip in the original Bronco II driveshaft???

Has anybody done this swap and point me in the right direction for the correct driveshafts for this swap?
 

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tw205

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New transmission is from a 4x4 ?
Old trans was TK5 ?
Manual transfer case or push button?
Are you using the original transfer case or the one from the ranger? Seems rangers have a double cardone rear output when broncos have that flat yoke. Using the original should solve the yoke issue.
TK 5 is not as long as the M5OD. This makes the rear shaft shorter and the front shaft longer. Shafts from an Fm 146 or A4LD fit with the M5OD.
 
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Joined
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Vehicle Year
1986
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Bronco II
New transmission is from a 4x4 ?
Old trans was TK5 ?
Manual transfer case or push button?
Are you using the original transfer case or the one from the ranger? Seems rangers have a double cardone rear output when broncos have that flat yoke. Using the original should solve the yoke issue.
TK 5 is not as long as the M5OD. This makes the rear shaft shorter and the front shaft longer. Shafts from an Fm 146 or A4LD fit with the M5OD.
Thank you so much for the reply!!!!

I was in a rush when I did the first post and didn't give the full description.

After doing a little research, the transmission in the Bronco was a FM145. Roughly 26" long.

The donor out of the Ranger is an M50D.

Definitely going to need new shafts. OR, we have the FM 145 rebuilt. She babies this ride and doesn't abuse it at all. Curious if the best course of action is to have the older transmission rebuilt. and stick with the original shafts.
 

tw205

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I have the same transmission in one of mine. Good solid transmission and will generally outlast the truck. I would rebuild and use it.
If you have a manual transfer case, FM145 and the TKs have a different shifter than the FM146 and A4LD. The M5OD will use the FM146/A4LD transfer case shifter as well as the drive shafts.
I have M50D in one of my trucks but it replaced an FM146 so all swapped over. The M5OD is a one piece trans so bell housing in not removable. V8 adapters will not work in a M5OD (FYI).
Swapping out any of the transmissions with the M5OD requires flywheel clutch and starter from the 4.0. (Another thing to consider).
 

tw205

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I just caught the front driveshaft output on the old transfer case vs new. Yes the ranger most likely has a BW 1354 transfer case with a double cardone front and rear. Using the original BW 1350 will solve those issues.
 

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