I do a lot of driving to get to my favorite hiking and camping places so could really benefit from an OD. One option is a ZF 5 which is stupid expensive now -$3K + $1K core charge. Option 2 is a Mazda M5OD2 for about $2K. Recently, I saw someone selling an oldie, an np435 with an over/under drive for about $300 - surely needs rebuild $$. From what I have read, the NP is tough as nails, maybe even stronger than the ZF, and certainly stronger than the Mazda. What are your opinions?

 

Surely you can find a Mazda far cheaper than that, while not the best towing tranny, it is still quite tough.

 

Soooooooooo...what engine, tires, gears, do you tow? This slab 4x4?

 

I have a 4.9l 4x4...I think the re is 3.08. That is what is stamped on the case, though the door jam says it is a 3.55. The price for the Mazda is a rebuilt one. I have seen some for about $1.4K

 

What 0D unit is on the 435?

 

1:1 is it for it, hence the external OD. NV has super low reverse gear and first. Basically 2/3/4 is what is useable normally.

Guessing this is in a half ton, so you are legally limited by towing capacity from the factory. Since you are 4x4, you could always use 2lo to back up a heavy trailer on an incline if you go with the M5OD

 

I would also like to know what over drive is bolted to the NP435
Is it in front or the back of the transmission?
Also any transmission you get will need to be for a 4x4 to bolt your transfer case to.

If at the over drive is at the back then this is a 4x2 transmission and not a 4x4 will your transfer case bolt up to the transmission?
Then will the over drive bolt to the rear of the transfer case?

I only know of 2 different bolt on over drive units.
Gear Vendor that bolt to the rear of auto or manual transmission or the rear of a transfer case and can only be used in 2 wheel drive not 4x4 mode.
You can split the gears once you are going over think 30 MPH. So the MP435 shifting 2>4 you now have a 6 sp transmission.

The other is Advance Adapter Range splitter over drive.
It bolts in front of the transmission between the bell housing and transmission.
Can only be used with manual transmissions but you can split all gear turning the NP435 4sp into a 8sp transmission.
Some of the ratios are too close together it is not worth splitting unless pulling something heavy or loaded heavy.

Yes I have the Advance overdrive and love it.
It did not help on the MPG as it did not change, AVG 15 MPG combo. 235/75/15 tire, 2.75 rear gear F100 flare side 4x2.
It did lower the RPM the motor spins and that keeps the wear done on the motor.
At times I pull a 20 ft enclosed 2 axle trailer and spiltting works out great then.

Would like to hear what over drive unit it is.
Dave ----

 

I would go with the mazda trans in that truck, because the 3 acceleration gears of the nv and zf really sucks. Although with 3.08s you may actually get some use out of the zf's granny 1st lol. Strength shouldn't be an issue in an f150 w/ a 300

 

As I remember the picture, the OD unit was mounted between the transmission and transfer case. The OD unit is described as a USGear underdrive unit that can be used either way (od or ud). It is 2 speed, with one gear being a 1:1, the other being either the over or under drive.

 

Having had a US Gear unit that was in my case an Overdrive it worked very well for splitting gears as well as a .72 overdrive. They are no longer in business having closed shop 20+ years ago. Mine was mounted behind a GM T400 and in front of an NP208 transfer case. They are either an overdrive or an underdrive but not both.

 

Well, if it's an underdrive, you'll have to change both final drives to set it up to get your revs down on the highway, so that's considerably more expensive...
If it's field- configurable to become an overdrive, THAT would be cool, assuming you can get the driveshafts that go with it.
Otherwise, factor those into the overall cost.
DO check your gearing- if you really have 3.08's, 4th ought to be pretty low revs on the highway. The M5od I have mated to a 4.9
with 3.55s isn't screaming down the road in 4th- and a 3.08 would drop that almost 20%. Dropping another 20% might actually
put the engine too low to make enough power for anything but 'downhill with a tailwind'...
Likewise, what transmission do you have in there now? a t18?

I will wholeheartedly second this. Having both the M5OD and the ZF5,
the M5OD is driveable in city, good on the highway, changes smoothly and has good gear spacing.
First gear gets used a lot, and it's in a good range.
With a 4wd truck, you end up using low range for many 'truck things' like backing a trailer or pulling stumps.
And that works just fine, keeping the strain off the transmission- it has the 1356, just like the ZF5, so THAT is also a win.
The only 'down side' is using manual hubs so that you can use low range without locking them.
Me, I put manual hubs on everything anyway, by preference, so it's all good.

The ZF5 is a heavy truck transmission, and demands to be shifted as such.
The wide ratio with a small engine (mine's a tired 351, so I imagine a 300 would be even worse)
is really hard on the clutch, as 1st is too low to be useful in normal driving, but 2nd is too tall to
get started against a hill, or to pull away from a light leisurely. The gear spacing is also truck- like,
with OD being a tall gear for going 75 (at 2200 with 3.5 gears)
4th being the only thing useful for highway speeds with a heavy load or much of a hill
and 3rd being good to MAYBE 55 while winding the crap out of the Windsor, something the 300 doesn't like at all.

A used M5OD and a 'refresh' kit of seals and bearings, and maybe a synchro ring or 2, and I think you'd be happiest
for a 'truck' that gets used for transportation. Now, for an F600 dump truck, that's a different story....

t
there's a distinction between 'disagree' and 'wrong' that many are unable to understand...

 

My vote still for 1356 and M5OD with 3.55:1 gears for tires to 31" on the 4.9. Should do all things well up to its legal limits.

Other stuff sounds too complex. I have a ZF in my dually behind a 7.3, it is a brute and not something one would like to DD.

 

I was thinking the same thing. Overdrive with 3.08 gears will be terrible and probably unusable except on flat ground.

A T18 is what he claims in there.


The OP has a thread from a couple weeks ago that asked about gearing. The door sticker says 3.55 gear but the tag on the diff says 3.08 gears. Apparently he hasn’t pulled the cover to see what is actually in there. The worst that happens is that you have to buy a gasket or gear oil RTV and a couple quarts of gear oil.

 

Yes, I have the T18.

 

Yes, I have not had the time or place to check that. I am living in an apartment now until I can find a house with a place to work on cars. The OD on the M5ODr2 is a .8 so it might be a little friendlier with the 4.9l Will my bw 1356 hook up to the m5odr2? Will I have to mess around with drive shaft lengths?