From a C4 to Manual Transmission

[Stlg67]

I have 1974 with a C4 and I was thinking about replacing it with a manual transmission with an over drive. I was just wondering if it would be worth it or not? I know several things would have to be done, like installing manual lever inside, as well as other things. I would like to have the shifter on the column if that could be done with an over drive manual transmission. Any advice would be greatly appreciated. Thanks

 

[ssray]

This might come down to how bad you want it. Five speeds are going to have a top mounted shifter coming through the floor. Column shift is not compatible with anything like that. New transmissions would be the AX15, or a model from Tremec. Used transmissions would be the 3550 or a couple Trannies from GM or Ford that would be more truck like.
Also needed would be a flywheel, clutch, clutch pedal assembly, and hydraulic clutch kit. Some transmissions require a bell housing. Others may just need an adapter plate. A body lift will also help with some transmissions to keep cutting the floor to a minimum. The driveshaft might also need modification or replacement.
There are lots of folks on here that I’ve done conversions and would have specific details.

 

[Stlg67]

Thanks for the information, I just seen on Bronco Graveyard that they offer a changeout kit with the AX15, I'm not sure exactly what all will be needed if I were to do this change. I would like a manual transmission instead of the C4, but I guess it will need some time to figure which way to go.

 

[bad 68]

If you hate automatics and want the fun of driving a stick i highly recommend it. You really don't want a column shift so good thing its not available. Nv 3550 Or AX 15 are both street And off road friendly. Don't recommend getting a used trans just buy the complete kit with brand new trans. Not much more money than used. You will need new driveline so factor in that cost on top of the conversion kit. If you can't do the install yourself or with a buddy than labor will be Additional and probably quite expensive. You can fit the trans by trimming the floor channels Without a body lift.

 

[badandy73]

I have 1974 with a C4 and I was thinking about replacing it with a manual transmission with an over drive. I was just wondering if it would be worth it or not? I know several things would have to be done, like installing manual lever inside, as well as other things. I would like to have the shifter on the column if that could be done with an over drive manual transmission. Any advice would be greatly appreciated. Thanks

If you're just looking for overdrive why not a modern automatic (4R/6R)?

I went from a C4 to a 4R70W this past year and it's been a game changer. Smooth as silk shifting compared to the harshness of the C4. Was able to keep the factory column shifter and have push button O/D on/off on the controller.

 

[Broncobowsher]

Column shift overdrive. Technically it is possible, but don't do it. I can think of 2 ways of doing it, neither is good. Both involve the 70's toploader 4-speed overdrive. It would be the external shift arm version. If you think old school 4-speed transmission they modified it so what would normally be 3rd gear is now an overdrive ratio and the step to 2nd gear is steeper. The Bronco 3-speed column shifter would be hooked up so the R-1 linkage went to the 1-2 arm, and the 2-3 linkage goes to the 3-4 arm. but flip the arm so it works backwards. 4-speed overdrive on the column. But you don't have reverse. You would need a seperate lever to get into reverse.
The other more unobtainium method would be to find a mid to late 70s chrysler that had a 4-speed column shift transmission. I have seen this in manuals, never seen one in person, only heard of one person who ever saw one in person. Then you would have an ugly chrysler column.
OK, while in the unobtainium parts hunt, there is a 3rd option but that would involve finding just as rare of parts from Australia. A co-worker was telling me that when he was young (he is old now) he worked for a short time in Australia and they had a truck that had a 5-speed column shifted manual transmission. But the shifter would be on the wrong side and you would have to flip the column to get the shifter and turn signal levers to be correct. I've never even seen paperwork on this one. No clue how the linkage or anything else in the column would transplant.
All of those ideas are HORRIBLE!

Next, you say you want an overdrive. Can you actually use an overdrive? What size tires do you have and what are your axle ratios? More than likely you already have too tall of a tire for the axle ratio you currently have. Trying to use an overdrive will be too steep of a gearing change and won't be useful. To get the whole package to work correctly, new lower axle gearing will be needed.

Is it the engine noise that makes you want the overdrive? More than likely the engine speed isn't that high, it is just fan noise from a direct drive mechanical fan that you are hearing.

 

[Stlg67]

I appreciate your reply, in the beginning I wanted a manual transmission but the wife found this bronco with the C4. Second trip out, the forward went out and had to go home in reverse, about 2 miles. That's the history of it. It works okay now since I rebuilt it 7 years ago. I would like to move towards and overdrive gear transmission either automatic or manual, whichever would be the easiest to change. I seen last night that Bronco Graveyard has a swap kit for the AX15. I emailed them earlier with some questions. I'm just looking for the best direction to go, I know it's going to cost but I'm willing to spend a little more to get there.

 

[Stlg67]

I don't mind the engine noise, just trying to get a little more economical on the gas, she wants to start driving it a little more than it's driven now. I still have to replace the rear breaks to disk breaks and a few other things. Figured I'd get as much to done as possible while in the repair mode.

 

[okorangebrnco]

I swapped a C4 to NV4500 back in 2005. It does great offroad and is fun to drive. However, it is not al fun and games. There are days I wish I would change it back to an auto for fun of cruising and less to do while wheeling. I have weighed it both ways over the last 7 years and I will likely change it back to an auto because of what is available now. I am not jumping out to make that my next project, but the NV4500 is like driving a truck.

Again, both have pro/con and they usually even out.

 

[Broncobowsher]

I swapped a C4 to NV4500 back in 2005. It does great offroad and is fun to drive. However, it is not al fun and games. There are days I wish I would change it back to an auto for fun of cruising and less to do while wheeling. I have weighed it both ways over the last 7 years and I will likely change it back to an auto because of what is available now. I am not jumping out to make that my next project, but the NV4500 is like driving a truck.

Again, both have pro/con and they usually even out.

A 6R would probably do you well. Still a deep 1st gear and overdrive. Presuming you have correct axle gearing to use an overdrive. Which after a couple decades of NV4500 I presume you have now.
You do make a point, not all manuals drive the same. NV4500, ZF, NP435 all drive like big truck transmissions. Gearing is still huge steps. Like the original 3-speed but with an extra low gear and overdrive. Car like manuals drive like cars. AX15, NV3550, toploader will have you driving it like a car.

 

[Stlg67]

With all this information, might just stay with the automatic or upgrade the C4 to a AOD. Thanks for all the information!

 

[73azbronco]

ewwwww, yeah, about fuel economy. You won't get any.

 

[Broncobowsher]

With all this information, might just stay with the automatic or upgrade the C4 to a AOD. Thanks for all the information!

What axle ratio and tire size? Very good chance that an AOD will be a horrible modification. Most broncos are under geared. The AOD doesn't add any more gearing where it is needed. The overdrive is one of the tallest overdrives offered. So tall it usually isn't useful. to make it useful takes regearing the axles.

The AOD is about the worst overdrive transmission that can be put in a Bronco. So many better choices exist. Can't even say the AOD is the cheapest choice either.

 

[badandy73]

Think what @Broncobowsher is trying to say is to go with the AODE/ 4R70W.