By Allen Wells
As many of you know, the 3spd transmission in stock form is not exactly what you would call “high performance”. Add a lift, larger tires, and then neglect to change the stock 3.50 gears and you begin to realize that this combination is destined to stay on the road because the gearing for offroading will force you to remain in 4-low just to keep from bogging down. Now, the correct thing to do would be to change your axle gearing to match your needs, but I like to do things backwards, so instead I wanted to change the transmission, and some day I will get to the gearing. My transmission was in really bad shape, with oil leaking from every orifice, plus the 2nd syncro has been gone for the past 5 years I have driven it. Not to mention that the placement of the aftermarket floor shifter makes grabbing the brake pedal in an emergency situation exciting to say the least. There are many available offerings out there for transmission conversions, and I looked at all of them before choosing the NV3550 available from Advance Adapters.
The NV3550 turned out to be the best choice for me for several reasons, including price, drivability, and the fact that I wouldn’t have to spend an additional $500 on new driveshafts. The NV3550 is almost $1000 cheaper than any other readily available Bronco 5-spd conversion (e.g., the NV4500 and the Ford ZF.). One issue to pay attention to is that the NV3550 kit is only available for the early style T-shift transfer case. Once you decide which transmission is right for you, the next issue to look at is where to purchase it. Since I live in Alaska, shipping was a major concern to me. I did some research and in the end found a shop in town that is an Advance Adapters dealer www.advanceadapters.com. Six States distributors www.sixstates.com is the shop I dealt with, and they were great, so if you have one in your area I highly suggest their services. They were able to include it in their stock shipment from Portland, OR--and save me over $150 in shipping charges!
The NV3550 kit came in two large boxes. Once you open the boxes, you’ll realize that Advance Adapters puts a great deal of time into packing their shipments. It took me about 30 minutes to break the tranny out of the expansion foam it was packed in. Take the time to inventory every item that is packed in the boxes, as the warranty period for the kit is only 90 days from the date of shipment. The reason I mention this is because I had a few things missing, such as nuts, bolts and washers. It sucks to be in the middle of something only to have to stop to dig through your scrounge or make a run to the hardware store.
Before you start this conversion, you should assess the condition of all of the other parts that must be removed for this conversion, because now is the best time to replace or rebuild them. In my case I knew I wasn’t going to reuse the clutch pressure plate or throw-out bearing so new ones were necessary. NOTE: The kit comes with a new clutch disc and pilot bushing. My Dana 20 had also seen better days so a complete rebuild was in order. I purchased a rebuild kit from Six States as well, which was a little cheaper than any of the Early Bronco suppliers.
Begin by disconnecting the battery, then remove the starter, complete exhaust system, clutch linkage, transfer case and transmission linkage, both driveshafts, and the speedometer cable. After that, remove the transmission and transfer case. A transmission jack is highly recommended. Once the transmission/transfer case has been removed from the rig, separate the t-case from the intermediate housing while being careful not to lose any of the 13 needle bearings from inside the t-case. Remove the snap ring and gear from the spud shaft on the intermediate housing and keep them handy because these mount on the newly supplied spud shaft. If you plan to rebuild the T-case, this is a good time to do it. Move the 3spd and intermediate housing aside--you won’t need these again until you buy a boat; I hear they make nice anchors. Remove the bell housing and all clutch accessories at this time. If you don’t have a tool to remove the pilot bushing, you could try; the tip I received from the www.broncofix.com mailing list: fill the hole with grease and pack it tight, then find some sort of dowel to fit in the hole and pound it out. I used a 3/8 to ¼ inch step down and a 13 mm deep well socket. Once all this is complete, it’s a good idea to go ahead and have the flywheel turned. Put the new pilot bushing in (I was able to tap it in with a large socket.) * Install new clutch disc and pressure-plate and torque to specs 23-28 ft lbs. making sure to use the clutch disc alignment tool. I went to a clutch shop to get one of these and they were only able to line up the splines and not the pilot bushing size, so I had to improvise with tightly wrapped electrical tape. Yes, it worked.
Next, put the NV3550 up on a workbench and install the transmission to bellhousing adapter using LockTite and torque. Since no specs were given I torqued the bolts to 40 ft lbs. I didn’t want to go too crazy, since it is an aluminum housing. Next test fit the bell housing to the transmission. Notice that the transmission shift rail doesn’t want to fit in the bell housing. Take a sharpie type pen and mark the housing. Cut the hole using whatever you desire. I only had a Dremel so it took me a while to size the hole appropriately. Make sure not to cut into the bell housing centering hole while cutting. I had approximately ¼ inch of metal left when the shift rail fit, just for your reference. After a proper fit is achieved, set the bell housing aside. Take the transmission-to- dana-20 adapter and fit it to the transmission. *Mark the top two holes and the bottom two holes. The spacing on 5 of the holes is 3-3/8 inches and one is 3-5/8 inch. Don’t install the adapter at this time, as it must be installed on the t-case first. At this time put together the spud shaft with the seal, bearing, o-ring, gear and snap ring from your original transmission as per the picture supplied with the instructions. Be careful when installing parts in the small housing as it is aluminum and is very soft. Once this is complete grab the dana-20 and make sure all 13 needle bearing are still installed properly. Slide the spud shaft into the t-case and lightly tap with a plastic mallet, while keeping it level. Once that’s done test fit the t-case with the transmission and place it in the properly clocked position as per AA instructions. You’ll need to trim the supplied gasket for it to fit over the spud shaft housing, about 1/8th inch on the inside diameter. Use RTV on both sides and LockTite on the bolts. Once again I torqued these to 40 ft lbs. Set dana-20 aside.
Next you’ll need to testfit the crossmember. *If yours doesn’t fit like mine didn’t, skip this step for now. Check the 8 attach points on the frame and chase them with a tap if necessary. Then cut the hole in the tunnel cover by making a template from measurements off of the transmission with the bell-housing adapter installed on the transmission. Temporarily install the bell housing on the engine to properly space the tunnel cut-out template. Place template on tunnel cover and mark with a sharpie. Cross your fingers and make the cut. Remove the bell housing.
Install the bell housing to the adapter and transmission, using LockTite and torque. Once again no torque specs so I went to 40 ft lbs. A buddy and I attempted to build a jack adapter for the tranny and t-case but in the end it was a waste of time. We then just decided to install both separately by hand. Remove the four 8mm bolts that hold the shift tower on and put a clean rag over the orifice to keep out debris. This makes installation a lot easier. Make sure the shift tower will fit in the hole that you made for the shifter; if it doesn’t, clearance it a little more. For the next step an additional set of hands is necessary. Once the tranny is in position and a few bolts are started, position a ratcheting strap forward of the cross member area around the frame in a good position to hold the weight of the transmission. Now you can wiggle the tranny around to get the bell housing alignment pins installed. Install the rest of the bolts and tighten. Now install the t-case in the properly clocked position aligning the marks you made earlier. Start a few of the bolts to keep it from falling on your head. Take the two longer bolts with the spacers and t-case shifter bracket and install on the drivers side upper two bolts making sure to place the spacers between the bracket and the transmission. I was unable to use a torque wrench in this area so I just put a little elbow into it. Install the t-case shifter now, since there are no driveshafts or cross member in the way. I had an extra shifter that the previous owner had modified to get rid of the t-handle. This turned out to be necessary due to clearance problems with the new 5-spd shift handle. *Once the handle is installed, connect the shift rod from the t-case to the handle with a washer and a cotter pin.
Now you’ll have to deal with the cross member. First install the transmission plate to the transmission. Again, I torqued the bolts to 40 ft lbs. Then loosely install the rubber mount to the plate. Next is the cross member and in my case it absolutely refused to cooperate. The cross member was about 1/8th inch wider than the frame rails. I had to grind off the powder coating on the outboard edges of the cross member and take a little extra off the top edges at an angle to get it started. Then I cleaned up the inside of the frame rails. Next, I used two floor jacks, one to support the t-case and the other to jack the cross member in place. The jack would only get it started; from there I used a dead blow rubber mallet. It took about 45 minutes to even get the first bolt started. It was a total SOB! * I set the torque on these 8 bolts to 40 ft lbs as well. Now it is time to put it all back together!
Do a reverse of what was done in the beginning, remembering to check every nut bolt and fastener of any kind twice. *When it is complete, take it on the road for a test drive and smile, because now you have a nice quiet and smooth transmission. Not to mention the fact that some of your bronco friends may finally be envious of your rig. An important thing to note is that after a certain amount of mileage (I checked at 100) check every bolt that you’ve touched and don’t forget to check all fluid levels. A special thanks to my buddy Brandon, because if it wasn’t for his help, it would have gone to a shop to get finished!
The instruction book in my opinion was horrible. If they spent half as much time writing the instructions as they did packaging the transmission and all the accessories, it would have been great. This alone was my reason for wanting to write this article.
When I removed the pilot bushing and matched it with the new one, it was apparent that AA had sent the wrong one. I thought I was going to have to have a custom one built, but once AA was called they corrected the problem. From phone call to doorstep (in Alaska) in less than 36 hours.
The transmission to Dana 20 adapter has six holes in it that mount to the transmission. At no point in the instructions does it mention that one hole is spaced differently than the other five. At a quick glance they all appear to be the same. When I put it all together I was one hole off and wasted several hours removing all the parts to correct it.
The cross member was a large pain. I cleaned off the powder coating on the outside edges and then beveled the tops. I used a floor jack and a block of wood to get it started. Once it was started, any more pressure just seemed to bend the cross member, so I had to persuade it the rest of the way with a rubber dead blow mallet. Occasionally I needed use the floor jack again. It took a long time to get it up in there so be patient.
The T-shift handle in my case appeared to hit the new 5spd shift handle rod, plus you won’t be able to use the old push button lock. I ended up using something that the previous owner had fabricated from an old shifter and a Hurst handle. It provides plenty of clearance. The other issue turned out to be the rod between the t-case and the shifter handle. The ends didn’t sit at the proper angle to match up. I believe this is from the change in mounting location. I used a propane torch to heat it up and get everything lined up.
There are 8 bolts for the cross member to frame and four of the flat washers were not supplied, plus 2 of the lower holes were close to the bend so a smaller washer needed to be used.
Because of the change in mounting for the t-case shifter the floor required more trimming. About an inch towards the driver’s side and 1.5 inch back. On the first test-drive the shifter made some noise because it was rubbing on the body, so I had to do a little more trimming.
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