85 d100 engine swap
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Rookie
Joined: Jan 2012
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85 d100 engine swap
I bought an 85 dodge 100 and put a 4" rough country lift and redid the truck. It has 31x10.5 tires on it and I would like to go to 35x12.5 tire in the future but I dont want the 318 thats in the truck to be turning that big of a tire. The motor runs great but Id like to put a 440 and trans on the truck in the future but Im trying to figure out how much has to be changed. Also how can I figure out what the gear ratio is on this truck. I cant read the numbers on the tags anymore.
Legend
Joined: Jun 2009
Posts: 8,025
Likes: 72
From: orangeville ontario
if you want to install a 440 you will also need a transmission and possibly the correct transfer case to bolt to that. i think if you where to stick a 440 in there it would not really matter what gears you have. that 440 would more than likely be able to turn them easily with 35's.
Champion
Joined: Mar 2009
Posts: 2,639
Likes: 4
From: Bent Mountain Va
Put the truck in neutral and raise one rear wheel. Rotate the raised rear wheel one revolution while counting the revolutions of the drive shaft. 3-1/2 revolutions of the drive shaft would be a 3.55, 3-1/4 would be a 3.23, 4-1/2 would be a 4.56 and so on.
Captain
Joined: Mar 2006
Posts: 546
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With the right gears your 318 will turn 35's no problem; stopping is the real problem since your light duty alxes and brakes will have a hard time stopping all that weight. Depending on what your plans are for the truck re-gearing or replace your axles with D60's will be cheaper and easier.
My 1988 started with a 318 and 35's with 4.56 gears and had no problems. With the original 3.55 gear ratio it was a slug! Even with a 440 it will still feel under-powered with a poor gear choice.
As far as a 440 swap you will also need a big block trans but then you are limited to the 203 transfer case you can use unless you swap the tail shaft and housing to be able to use a newer 205\208\241 case. Your other choice is a 2wd trans and a divorced 205 case but this will require more modifications, 3 drive shafts, 2 cross-members, etc.
You will also need these parts as shown in this kit:
http://bouchillonperformance.com/BPEtruckKit.asp
My 1988 started with a 318 and 35's with 4.56 gears and had no problems. With the original 3.55 gear ratio it was a slug! Even with a 440 it will still feel under-powered with a poor gear choice.
As far as a 440 swap you will also need a big block trans but then you are limited to the 203 transfer case you can use unless you swap the tail shaft and housing to be able to use a newer 205\208\241 case. Your other choice is a 2wd trans and a divorced 205 case but this will require more modifications, 3 drive shafts, 2 cross-members, etc.
You will also need these parts as shown in this kit:
http://bouchillonperformance.com/BPEtruckKit.asp
