Need help with gearing please
Cargo Master
Joined: Feb 2006
Posts: 3,009
Likes: 250
From: North Pole, Alaska
You gotta remember that these engines were designed to run 3000-3500 RPM under load, all day long. As gump1376 points out, at 3500 RPM your going a lot faster than 48 mph. At 3000 RPM you'd be at 61 mph. If I had that set up, and money, I'd be looking at an NV4500 trans swap for the overdrive. If you have a divorced transfer case you probably have enough room for a Gear Vendors OD on the back of the NP435, which is what I'd look at if I had lots of money. My '67 has a 240 six and NP435, with 4:56 rear end gears. I run 33" rear tires and a tach, and got used to hearing the engine at it's designed RPM range. It sounds a lot worse than it really is.
Cargo Master
Joined: Feb 2006
Posts: 3,009
Likes: 250
From: North Pole, Alaska
A GV is too long at 12.25" for the base unit, and would cause angularity problems on the rear shaft u-joints due to the TC having to be shoved back, unless you have a Crew like I do.
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7th Gear
Joined: Apr 2023
Posts: 7
Likes: 0
You gotta remember that these engines were designed to run 3000-3500 RPM under load, all day long. As gump1376 points out, at 3500 RPM your going a lot faster than 48 mph. At 3000 RPM you'd be at 61 mph. If I had that set up, and money, I'd be looking at an NV4500 trans swap for the overdrive. If you have a divorced transfer case you probably have enough room for a Gear Vendors OD on the back of the NP435, which is what I'd look at if I had lots of money. My '67 has a 240 six and NP435, with 4:56 rear end gears. I run 33" rear tires and a tach, and got used to hearing the engine at it's designed RPM range. It sounds a lot worse than it really is.
Tuned
Joined: Mar 2018
Posts: 411
Likes: 48
From: NM
Those Advance Adapters Ranger Overdrive units are difficult to find now that AA doesn't make them anymore. I found one for a project I will be doing once my 71 is done, but I had to search several websites and adds before I found one.
Tuned
Joined: Mar 2018
Posts: 411
Likes: 48
From: NM
I'm not sure why the NV4500 over the ZF5. Both have similar torque ratings, but the ZF5 will bolt right up without any adapters. May need to add a clutch master cylinder and slave cylinder to operate the throw-out bearing arm, but that isn't too bad.
Cargo Master
Joined: Feb 2006
Posts: 3,009
Likes: 250
From: North Pole, Alaska
The NV 4500 uses a mechanical clutch so it would be easier to retrofit for the NP 435 exchange. The ZF must use a hydraulic clutch which is harder to integrate with an old truck. The ZF also has an integral bell housing so the proper version must be sourced.
Cross-Country
Joined: Aug 2021
Posts: 69
Likes: 18
From: China Lake
I was thinking along the lines of RichS2659 on the trans thing, that the NV4500 would be an easier and less costly swap. There is another thread here, "240 with M5R2," where a 5 speed with hydraulic clutch was successfully installed behind a six (I haven't looked too hard, there are probably others as well). Doesn't seem too hard to do the hydraulic clutch master cylinder, and the ZF trans should be quite a bit stronger.
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Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
Nice catch Rich. I see the top of the 1978 and newer Ford CII p/s pump also.
While an O/D is a good idea, I would go right to the root of the problem. The front and rear axle gearing. Now that that rig is "retired" from duty, that gearing isn't necessary. I'm not doubting you OP, but how do you know both axles have that ratio?
While an O/D is a good idea, I would go right to the root of the problem. The front and rear axle gearing. Now that that rig is "retired" from duty, that gearing isn't necessary. I'm not doubting you OP, but how do you know both axles have that ratio?
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