One thing that always bugged me about my Bronco was the transmission. It came with the aluminum SROD transmission. With no low gear, and the 3.00 rear, it didn't have a whole lot of grunt until I went into low range. Plus, the transmission's housing is somewhat weak, and the torquey 300 had already broken the mounting tabs off of it. I had the mighty 300, the stout 9" rear, and it was linked together with a weak transmission. No good.
Well, now that I had 31" tires, the RPMs in overdrive had become so low that I almost never used it, effectively leaving me with a 3 speed. 65mph was around 1500 RPMs, which seems nice and low, but it dropped the engine vacuum enough to where I was always in the power circuit of the carburetor. Any gas mileage gains from low RPMs was lost from the carb dumping more fuel to turn the engine.
Well, one day I pulled into my parking space at work, put the clutch to the floor and immediately heard a loud *CRUNCH
*. The pedal snapped to the floor and stayed. I immediately turned the engine off and left it. My Bronco had never let me down before and this was no different. I could have been in the middle of the road, shifting on the interstate, who knows. But it waited until I was safely parked at work.
Turns out later, my throwout bearing was toast.
So, I knew I was going to have to pull the transmission and decided while I was at it, it was time to change things up. Luck would have it that I found a parts truck for $300 that came with both a 300 and an NP-435 transmission. Plus, it was a hydraulic clutch, which was an upgrade from my mechanical. I was able to drive it 30 miles home, which let me know what condition it was in. Despite being hideous, it ran like a top. Time to swap it all in!
The truck was at my brother's house, since I didn't have a place for it, so once I pulled it, I had to haul it all home. Took a couple trips.
The shift towers are completely different, so I needed that too.
In fact, every single part was different. I needed the transmission, bell housing, shifter tower, pedals, and the floor mat. I also grabbed the NP-208 out of it since mine had been jumping chain teeth.
First step was cleaning up the engine.
New flywheel, pressure plate, clutch, etc. I also put all new gaskets on the engine I was putting in, including the head gasket. I wanted it to be good to go.
The current engine was rattling and making all sorts of noise, so I decided to swap it out.
The *new* one in place.
I thought that was the hard part. Now for the transmission swap. One of the most tedious and painstaking tasks I've ever undertaken. It wasn't necessarily hard, it was just that no matter how much I did, there always seemed to be 20 - 30 more steps ahead of me I hadn't done yet. I took time off of work to finish it and the swap honestly took around three to four 8 hour days. I was beat.
Inspecting the NP-435 gears. I had no idea what I was looking for (never seen inside a transmission), but it didn't hurt to look.
The NP-435 is around 120 lbs. It wasn't the easiest thing to move around. The SROD, on the other hand, is around 50. The size difference between the two was impressive.
Unlike the SROD, I had to jack up the Bronco to get the NP-435 underneath it.
I needed to swap shift towers since the SROD shifters are in a completely different location than the NP-435. I also didn't want holes in the floor mat, so I needed the entire floor mat as well. I couldn't believe my luck that the parts truck had a black, rubber floor mat exactly like mine, plus it was in MUCH better shape. So I was able to swap it right in.
Once the transmission was in, I swapped in the transfer case. I noticed immediately that the tailshaft was different due to being out of an f-series truck.
Not to be deterred, I swapped the tailshaft from my Bronco t-case over. I'd never been inside a transfer case before, but it was surprisingly straightforward.
The shaft on the left needed to come out, but the chain has NO flex, so the gear on the right needed to come off.
It's simply held on by a big C clip.
Once the gear was off:
The tailshaft came out:
Once it was all swapped around, I buttoned it back up and put it in:
All bolted up and in place.
Not to be left without more steps to do, next was the hydraulic setup:
The bell housing's were about 95% the same, save for the provision for a hydraulic slave cylinder.
Using the gasket as a template, I measured where the master cylinder needed to go. If I was off just a little bit, it wouldn't match up with the pedals on the inside.
Drilled and in place:
I'm going to skip over some of the nightmare I had getting the clutch arm in place, as this has gone on long enough. But let's just say that Ford discontinued a part that the service manual specifies is to be replaced EVERY time it is removed. As you can see in this pic, the new clutch rod has splines on the end. The arm that is hanging slides onto the splines and the grooves are cut AS you tighten it down. So, if you remove it and try to put it back on, it strips out like butter. I tried welding it at first, but that was a waste of effort. Finding a new arm proved fruitless, so I finally pulled an entire pedal assembly from the junk yard that still had the arm in place.
Lastly, getting the clutch spring back in place. I can't tell you how many times this thing shot out and hit me before I finally tamed it.
After that, I cut the wires and it popped into place.
All in all, once it was done (which I was glad it was), it was the best thing I've done for my Bronco (aside from going with a 4bbl). The transmission shifts like butter, and everything about it just feels strong
. With the granny gear, I went from a crawl ratio of 25.4 to 52.4. I love the hydraulic clutch. And with a 3.00 rear end, I'm still only at 2500 RPMs at 75mph.
Tough as nails, just like it should be.