I'm researching ways to add an overdrive to my 1984 F-150. It's a 351w paired to an np435 with a np208 T case. It came factory with a 3.50 axle, and I don't think I want a higher ratio. So I'm struggling to decide between finding a ZF-5, getting a gear vendor, or adapting a TR-4050. ZF5 would be cheaper, but no guarantee of finding one. The gear vendor would be the most effective, I think since I could also split gears but then there's a strength/reliability concern. The Tr-4050 would be the most expensive but they seem to be popular for 4x4 applications, so they must be sturdy and there are adapters to hook them up to Ford bellhousings. What's the common consensus?

 

Do you feel you need a high strength transmission? The zf is a very large transmission. It will require the special floor pan from the donor, or you will have to modify your floorboard cover for it to fit. A more normal transmission would be the Mazda 5 speed, the M5OD.

This 4050 transmission. Will you buy it new? Will you be able to bolt your NP208 to it?

What state do you live in? There are about 3 pages of 5.8 zf 5 speeds around the country on www.car-part.com

 

I'd rather know it can handle me overworking it a bit. And at least when I stumble through the website, there's no small block 4x4 zf5's within a reasonable range of my neck of Montana. if I were to go all in with the tr4050 i'd probably just get a Chrysler spec t-case.

 

Is your 351w stock or have you pepped it up a bit.
do you need the granny 1st gear?
if not then I feel like the Mazda m5od may fit your needs.
I know they are said to be weak, but I also think that is a unfair assessment.
I have been running a Mazda m5od behind a 351w for a while now and the transmission has not been a problem.

An example of what i am putting thru the m5od transmission

Another view of the dyno runs

3.55 ring and pinion destroyed due to weak springs and wheel hop.

Another view
Then transmission still works as intended.

 

In full transparency my truck is a 74 2wd not an 80s 4wd.
also the engine has been bored and stroked to a 410
I don't want to mislead anyone.

 

Also those are rear wheel numbers as the pulls where done on a mobile chassis dyno

 

I would say if you dont need the granny first to go with the M5OD as it was also used in F250 trucks so it must be strong enough to handle what you need.
If you need the granny then go for the Gear Vender but note it can only be used in 4x2 mode NOT 4x4 unlike the M5OD.
But you can split the gears when going 30 MPH as it has a safety that it will not go into OD below that speed.
And dont worry about if it can take the power of not as there are people out there using them in drag cars they drive on the street.
I bet if you do a YouTube search for GV OD you will came up with some

I wished Advance Adapter still made the Range Splitter over drive as you can use it in 4x4 mode and works great with the NP435 as I got one of the last ones.
Dave ----

 

Yea i was very disappointed that they don't make the splitter anymore. I'd heard that the m5od was very weak, maybe it was a case of Internet hyperbole. I really like having the granny gear but it's not strictly necessary. Presuming i were to go with an m5od don't they have a centrifugal slave cylinder? Could i just use a clutch hose from the donor truck? I don't think being unable to split in 4x4 would bother me too much i don't tend to run around in 4x4 unless i need it.

 

It's a roller block from a 97 so it's got an edelbrock performer intake and avs2 carb but aside from that it's stock. It won't be for much longer though. I don't strictly need the granny gear but i definitely benefit from it though. Maybe i need to reevaluate the m5od I might've fallen victim to internet fuds and formed a poorly informed opinion.

 

I haven't owned either, but there are two versions of the Mazda trans...............M5OD-R1 & M5OD-R2.

The R2 version is heavier duty (F150's), while the R1 version was used in Rangers etc

 

You might be thinking of the SROD / 170 trans that is a 4 speed over drive that is a weak POS and I would run from one. Heck I got one from my parts truck, dont know if any good or not, and I dont plan to use it in anything ATM.

I know all 80-86 used a hydraulic slave on the outside of the bell housing.
Now DaveF said the later hydraulic clutch trucks use a hydraulic throw out bearing inside the bell housing.
I dont know how true this is as I have never looked that deep into it but I cant see that being a problem as long as the matching master is used.
I also know of a member (Rembrandt? / Cory) that has done 2 M5OD swaps and I dont remember him having any problems with the clutch. I know 1 was a 4x4.

Being I was building my truck to also pull my 20' open deck car trailer I wanted the granny first gear. The granny gear also helps as I have a 300 six and 2.75 rear gear to get heavy loads moving.
If I was building a truck just to drive on the street I would not thing twice about using the M5OD.
If it was in a 4x4 and used off road you would use low range and if in 4x4 on road you would not be going that fast in high range to maybe use over drive.
Dave ----

 

I'm aiming for this truck to be able to do a little of everything, light towing, as much off roading as one might need for camping, and still be something i enjoy just driving around. I know the 2wd zf5 i had in a f250 had the hydraulic throw out bearing so imagine the lighter trans does too. Towing brings up a relevant question, I've been wondering if i can rely on my f150 to haul a car or two i pick up for projects. I'm pretty sure I'd need to put new leaf springs in the ones it has are wore out but, i don't know if the brakes can keep a 15-20 foot trailer and a car under control.

 

Being you have a 351 and think you said 3.55 gears should not be a problem and depending how often you plan on towing a car or camper and how far you might want to keep the NP435 with the granny first.
This way you are not slipping the clutch to get the heavy load moving, that is why I love the granny first in my NP435.

A Gear Vender over drive would be the easiest and fastest and only need to get a new rear drive shaft. Remember the over drive fits on the rear of the transfer case between the case and rear drive shaft.
If you go with a M5OD or a ZF5 it would have to be for a 4x4 so you can bolt your transfer case to it, need all the little things like crossmember & brackets, floor pan, and maybe replace both drive shafts.
Other than the drive shaft they say the GV OD can be done in a weekend and to me maybe a long 1 day job.

As for brakes most if not all state laws say 15 to 20 foot trailers need brakes and with the weight of a car I would 100% say you need trailer brakes.
I knew I was going to use my truck to pull my car trailer, 20' open deck that has brakes on 1 axle, so I added a electric brake controller to it.
I have not pulled my trailer but the car club support trailer, 20' enclosed that has brakes on both axles, and with that is no problem stopping.
My car trailer is set up for a WD hitch bt the club trailer being a V nose my bars are to long so cant fit the brackets to it
Club trailer I pull on local roads, max speed 55 MPH but I did just browed a dual axle flat bed, no brakes, loaded pretty good on the high way 50 miles each way without problems.
Thing was in over drive and the rear 2.75 rear gear ratio 65 MPH was about as fast as she would go, most big rigs are limited to 65 MPH so not a big deal to just hang with them.
So as long as you have the load loaded right you sould not have any problems.
BTW the club trailer will make my truck squat a little but it only levels out not any more.


Dave ----

 

Alright, that's comforting, I'll probably keep the 435 at least for now, if a zf5 falls into my lap I'll take it otherwise I'll just do the gear vendor. I think the first gear on the zf5 is cloe enough to the np435 especially if i put 3.73s in that i should be fine for how often I'll tow. Where'd you get your trailer brake controller from?

 

Brake controllers are all over the internet, Amazon, etc. The choice in brake controllers is how much do you want to spend?

I buy the cheap controllers that work on a timed ramp for the trailer brakes. You hit the brakes and the controller slowly brings in the trailer braking on a timed curve that you can adjust.

Then they have the pendulum type controllers. They are the ones that must be leveled when installed. As you hit the brakes inertia swings a pendulum inside the controller that determines how hard to apply the brakes to the trailer.

The highest priced ones have a electronic device that determines how fast the truck is coming to a stop, and adjusts the trailer brakes accordingly.

That's the trick to the whole trailer controller, to coordinate and make the trailer brakes work with the truck. On most all of controllers, you will have to adjust them when the trailer is unloaded, and then when it's loaded to get the best balance between the truck and the trailer. And all of them have a manual button where you can apply just the trailer brakes. That is a must feature if the trailer starts swaying out of control.