D100 Pickup question for you:

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Michael Brisebois

Michael Brisebois

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I recently bought a 62 D100 from an old rancher in Montana and trying to do it justice. This is my 3rd Mopar project and since there's no "fordbodiesonly.com" ( I don't seem to get much from fortrucksonly.com), I'm hoping for an opinion regarding my drivetrain from the place that has helped me most with my car projects.

It's a 250 slant with a 4 speed trans. It's the 4 speed with a granny gear....which is at the heart of my question. I HATE changing what the Chrysler minds have assembled, but the granny gear is of no use to me. I grant myself the right to change things regarding safety...that's about it, but I can't help but wonder if changing the gear ratio in the differential would make the "super low" gear, to be a....more of a real 1st gear and perhaps it wouldn't sound like the rpm's are max'd out at 60 mph. I'm not building a hotrod, at all.

I would really like to keep the original trans....Does anyone have experience, or advise to share?
Your wisdom is appreciated.
 
IMHO, it all depends what you are going to use it for. If you are going to use it like a pickup, with the leaning tower of power it would probably be a good idea to keep the transmission. Low gear can be a godsend. If you are going to use it as a driver and you have something against starting in second gear, then I'd just change transmissions and be done with it. IIRC there were two four speeds available in '62, the NP420 that has 3rd and 4th synchronized and the NP435 that has 2nd, 3rd, and 4th synchronized. Over the years, 2nd gear in the NP420 gets beat up and eventually won't stay in gear under heavy acceleration.

But good purchase. A '62 short bed Utiline is one of my favorite trucks.
 
Granny low can also be used and appreciated if starting from a stop on a steep hill, pulling someone out of a ditch, if stuck in mud or another slippery surface, etc.

Mine with bald tires will move on wet grass up a steep grade in low easy, 2nd is a waste of time for me in that situation.

(painting the wheels now for new tires before Spring though)
 
I have a similar truck but newer, an 82 D150 with a slant. The trans is the 833OD which works OK around town but I've already figured out if I'm hauling any weight or pulling my trailer, first gear is too steep to get going very well. If you're using yours as a cruiser, a different trans might be in order. If you're using it as a truck the granny gear is a good thing.
 
It probably has 3.91 gears and 60 mph is all you’re going to get. I’ve sometimes wished I left my 64 alone. If you’re planning on around town and such, then leave it as is. It worked for 50 years, it will go another 50. My 2cents.
 
You really have to understand”intended use”. When yours was born it’s intended use was”truck”. Now years later you are changing its use without changing how it was built. The bodies have not got heavier but the frames/suspension/power train have changed quite a bit in fifty some odd years. Be realistic on how you want it to perform before you start throwing money at it. I have found that trucks are mainly modified and the best and most efficient way is to buy a rusty bodied late model and switch. But that is your decision to make
 
Same problem with my 71 D100 /6
Love the low end granny gear but would also like to have a "little" bit more high end.
Has factory 8 3/4 with 3.23's and was thinking about converting to 2.76's.

Would give me a little more top end and sacrifice low end.

Any thoughts/comments or experience regarding doing to my truck or any other same vintage mopar with a /6?
 
All good comments and thank you!
Mine is a short bed Utiline. It came off the line as work truck, for sure. This truck will have an easy life...the body is great and needs so very little. The only real work it will do, is hauling a cooler full of beer.

I'm really asking if anyone has had success with higher rear end gears, to require the use of 1st gear and resulting in increased speed in 4th.
 
For Trucks Only. Mostly Dodge trucks but it is open to all makes. Many truck owning members from FABO, FEBO, FCBO, and FBBO are over there too.

For Trucks Only Forum
 
Michael Brisebois said:
All good comments and thank you!
Mine is a short bed Utiline. It came off the line as work truck, for sure. This truck will have an easy life...the body is great and needs so very little. The only real work it will do, is hauling a cooler full of beer.

I'm really asking if anyone has had success with higher rear end gears, to require the use of 1st gear and resulting in increased speed in 4th.
Click to expand...
NO- the point I made is you are not changing enough to achieve what you want./6 being a great engine is only one part of the equation. The miser trucks coupled a /6 with an overdrive transmission achieved the other side of the spectrum. It’s your money spend it however you want but it’s a system be honest with what you want and you won’t be disgusted with your results
 
They DID make a later model higher-first-gear model of those "truck" transmissions, maybe you could swap one of them in. It would keep the "truck" appearance and give you a "more useable" first gear.

Read this:

The Novak Guide to the New Process 435 Transmission

1st 2nd 3rd 4th (direct) Rev.
NP435A (Dodge, GM) 4.56 2.28 1.31 1.00 5.64
NP435L (Ford, Dodge, GM) 6.68 3.34 1.66 1.0 8.26
NP435D (GM) 4.90 2.29 1.19 1.00 6.06
NP435E (Ford) 6.68 3.34 1.74 1.00 8.26

Or you could swap in a later model A833 overdrive 4 speed, which was used in some later model trucks. Of course you need to be sure the /6 has enough oomph to pull whatever rear gear is in the thing.
 
Let's do some math. If you have the 420, which I suspect you do, first gear ratio is 6.68. Couple that with a 3.91 rear and you have a combined ration of 26.12. Now looking at a car with a 2.66 first gear and a 3.23 rear, you have a combined ratio of 8.59. How high a rear end ratio do you have to have to get the equivalent of the car combined ratio? It doesn't exist. Even with a 2.76 rear you have a combined ratio of 18.44 or over twice the car equivalent. If you have the 435, which I doubt, the highest first gear ratio available was a 4.56 which coupled with a 2.76 still gives you a 12.59 overall ratio. It just isn't in the cards to get the equivalent of a traditional first gear by changing rear end gears.
 
Michael Brisebois said:
I recently bought a 62 D100 from an old rancher in Montana and trying to do it justice. This is my 3rd Mopar project and since there's no "fordbodiesonly.com" ( I don't seem to get much from fortrucksonly.com), I'm hoping for an opinion regarding my drivetrain from the place that has helped me most with my car projects.

It's a 250 slant with a 4 speed trans. It's the 4 speed with a granny gear....which is at the heart of my question. I HATE changing what the Chrysler minds have assembled, but the granny gear is of no use to me. I grant myself the right to change things regarding safety...that's about it, but I can't help but wonder if changing the gear ratio in the differential would make the "super low" gear, to be a....more of a real 1st gear and perhaps it wouldn't sound like the rpm's are max'd out at 60 mph. I'm not building a hotrod, at all.

I would really like to keep the original trans....Does anyone have experience, or advise to share?
Your wisdom is appreciated.
Click to expand...
With it being a 2wd, you could easily at the GearVendors OD to it, just a tail shaft swap.
 
And once again it’s a system that you are looking for. /6 which is the first problem-switched to a 904/727 then go with 3.55-3.23 will get you a drivable truck. But if you really want to put some cash into your /6 turbocharged is a great way to go. But drive it like it is it was not designed for 70 mph
 
mine 1.JPG
mine 2.jpg


The interior is being redone now
 
I ran a np435 behind a 383 in my rat rod for years. First gear was still useless with 2.76 gears. The 420 has an even deeper first gear. In a truck with a slant I would for sure keep the 420, to get you going in case you ever want to pull something or put something heavy in the bed.
 
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