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Discussion Starter #1
Just bought a very used 1970 Ford Crew Cab 4x4. (saw it had to have it) The truck is equiped with a 390, 4:10's and a Np 435 as a result the motor will be screaming on the freeway. What about an external overdrive or splitter unit. Does anyone out there run one? If so which one.
thanks for your time
fatguy
 

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You basically have 4 options:

1. Put bigger tires on it, and don't worry about the OD.

2. Swap the 435 for a 5 spd HD tranny (ie NV4500, ZF, etc), or a 6 spd. This would be nice and easy if its a divorce t-case.

3. Find an auxiliary tranny (ie a brownie) out of an older medium duty truck, and mount it between the trans and t-case (again, much easier with a divorced t-case). An added bonus is that these are often 3 speed units. However, they are generally manually shifted.

4. Buy an OD unit from GearVendors or US gear. IIRC, GV mounts between the trans and t-case (with adapters they sell) and is around $2000, and US mounts to the back of the t-case, and is around $2500. (I could have that backwards). I do know that GV cannot be used with an exhaust brake (which doesn't affect you), and that it cannot be used below ~30 mph. These units are electrically shifted (can mount the switch on your tranny shifter).

Pete
 

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If it were me . . .

I'd be looking at a nice set of LT285/75-16's or perhaps a set of 305's. That would put the effective ratio of those 4.10's in a pretty good spot for freeway travel.

But that would be the easy way and would still leave those big holes in the NP435 gear spread.

Cheap, though.
 

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Discussion Starter #4 (Edited)
Thank you both for your input. I will look into both options. The Idea of a five speed is great but aren't we talking some pretty high numbers $$$. Pete how does the brownie trans work out. the truck currently has a divorced t-case. Some more info on that would be great or at least a place to go and search.
thanks again
john
 

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I would think that a 5 speed conversion would be cheaper than an aftermarket OD.

There has been some talk at times about the auxiliary trannys/brownies on this board, you might try a search. Essentially, its an extra transmission thats designed to go behind the main trans, connected with a short driveshaft (similar to a divorced t-case. Its also been a topic of discussion on the TDR, but you can't do a search there unless you are a member.

Pete
 

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Another option -- find a two-speed rearend and kiss ground clearance goodbye.

Close-ratio auxiliary trannies are tough to find these days -- let me know if you find an extra, I might buy it!

Randii
 

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randii said:
Another option -- find a two-speed rearend and kiss ground clearance goodbye.
What could I get a 2-speed rear end out of? It would have to be something medium duty, and would be 10-lug, right? If there is an 8-lug 2-speed rear that I can get, I want one!

AKAFATGUY - I tow with a '77 Chevy rollback with 454, SM465, 4.10 gears, and 235/85/16 rear tires. The highway is not TOO bad if I limit my speed to 65 mph. Gas mileage sucks, and if I bump up the speed, it gets a lot worse really fast.

I agree with Jason Lockwood that if you use taller tires (or change the axle ratio) it will drop your highway RPM, but you'll still have big gaps in the gear pattern. I find that the gap between 3rd and 4th gear is what bothers me. Unloaded it is fine, and it's not really unbearable unless I have a vehicle on the bed AND one on a trailer behind me. I can make it work, but I just have to floor it when I hit a hill on the highway because I can't downshift until I'm below like 40 mph. If I'm over 65mph I can maintain speed on a hill in 4th no problem (go 454!), but between 40mph and 65mph hills can get a little slow. And I live in only mildly hilly terrain, and have never towed in the mountains...

Again - I can deal with it, I'd just rather be able to split gears and not have to deal with it! :D

Later!
Richard
 

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Sign me up for an 8 lug 2 speed rear two, I'd love to have one in the Dodge. With usable ratio's, of course. Maybe 3.08/3.73? :flipoff2:

I haven't looked too far into the aux tranny for my own truck, I'm kind of worried about adding that much more slop to the drivetrain, plus it seems like splitting gears would be kind of a PITA with two manual shifters.

Would a 5 speed really help with the wide gear split problems of the 4 speed (given the same gears and tires)? It seems all it would give you is a higher top speed. You'd have to go to a 6 speed to solve the gear split problems.

Pete
 

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Discussion Starter #11
Thanks again everyone! I'll do a search for auxillary trannies just to see what I can find. What would you suggest as the best auxillary tranny.
thanks john
 

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CrazyHorse said:
the 5 speed isn't an option with the 390, there aren't any that will bolt to the FE bellhousing pattern...
well, um, I suppose.
Add the dime a dozen FE to SAE adapter ring, and its a piece of cake.
 

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Sign me up for an 8 lug 2 speed rear two, I'd love to have one in the Dodge.
Geez, don't let that stop ya -- nobody in our hobby EVER runs different wheels and tires front-to-rear, machines up adapters, redrills axles, etc.

With usable ratio's, of course. Maybe 3.08/3.73? :flipoff2:
Now THIS is the complicated part... I haven't looked into this much. Even with the lower range rear ends, you could 2:1 uprate with a back-running 205.

Anything is possible, with creativity...

Randii
 

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First off.. there's NOTHING wrong with 4.10s and 235/85-16s.

I run 4.30 gears with 235/85-16s in my tow rig.

60-65mph is a good speed for a low-revving IH small-block 345 with plenty of power to haul the load.

Tires are CHEAP.. just saw an add on my way to work.. $60 for ATs in the 235/85-16 size. Dang..

LR-E, of course.

Sure, you probably won't be hauling at 85mph.. but should you anyhow? A friend with a 460 and 3.25 gears has to run 75-80mph (amazingly, he said that's faster than he likes to pull.. never thought I'd hear that from *him*) because the 460 won't run any slower.

Personally, I'd like to go a *little* taller in tire size to get a little longer "legs" - especially when unloaded, but it's really not bad.

I did pick up a Brown-Lipe auxiliary for the truck, but haven't installed it, and I'm not sure I will yet.




I thought I bought an OD unit, it's really a UD unit.. spec is 1:1, 1.3:1, and 1.5:1

I couldn't find the 1.5 gear - I have a neutral (haven't popped the cover off yet, either).

I'm *thinking* of mounting the brownie backwards behind my t'case (truck is currently 2wd, getting converted to a 60 front and divorced NP205, but I don't want to put the brownie in between.. I'll use the factory NP205 brackets, driveshafts, shifters, etc and keep it cheap).

Running it backwards, will give me a .77 OD gear.

I think it'll split the 3-4 shift (EVERYONE hates that in a wide-box T18/T19) just as well going 3-hi as it would going 4-low.

Bonus, I'll get those longer highway legs.. with an effective 3.30 final drive.

I've just never driven a brownie, and I'm still not real clear on how easy to shift this will be.

If I mount it backwards, I'll probably cheat.. and go with an air solenoid mounted to my T19 shifter for the direct/over switch.

Best spot behind the '205 to mount the brownie is under the front of the box.. and my truck is also a Crewcab, so that's a long ways back. I don't think heating the shifter with a torch will get me what I need. :D

So air-shift seems a natural.

Just need to make sure I'm capable of double-clutching reliably and consistently with two transmissions in the mix. I can shift one w/o the clutch just fine..

Plus I'll be wanting to slam gears when I downshift from 4-direct to 3-over when pulling a hill.. or upshift from 3 to 3-over. It'll suck to slow down so much I have to back to the gear I was in already..

I have that situation now with the 4spd. :)

As for mileage.. my '74 IH Crewcab is shaped like a brick.

The faster I go, the worse the mileage gets, so the deep gears just keep me in the power band *and* keep me from pushing too much wind.

I drove the truck with a tired 2bbl 345, wide T98 4spd, 4.30 gears, 235/85-16s, my 16' flabed with my lifted Scout.. tons of parts for sale/trade, tools, camping gear, etc.

14,000lbs on the scales.

Took that from Montana to Colorado to Moab and back last summer.

60-65mph through Yellowstone, Wyoming, Colorado, Utah, Idaho.. slower up the hills with that pathetic 3rd gear..

I averaged 9.5mpg with the trailer, and I think 12mpg on one short section where I didn't pull anything.

As long as I'm teetering on double digits, I'm happy.

The year before, I pulled a lot less weight, using a Scout II to do the pulling, with 4.09s and 33s and a freshly built 345. Probably 10k total gross.

I got 8-9mpg.
 
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