What have you guys/gals seen as the most common gear ratios for the 1st gen 1/2 ton 2wdtrucks with the 318's and autos?
I cant find any info on mine yet(no axle ID tag to be found) and I havnt pulled the diff cover or even spun the tire and counted the drive shaft revs. just curious as to what you have seen as the mostcommon. thanks

 

My 1988 came with 3.21

 

My 87 D100 came with 2.76.

 

Probably 321s or 323s. There is an easy to tell what ratio you have. Take a piece of chalk or white marker and mark a line on the end of the drive shaft where it meets the yoke in the rear end, the mark must also line up on the rear housing (straight line) then mark a line at the 12:00 position on either trie, raise the one wheel off the ground and slowly rotate it clock wise and count how many times the chalk mark on the drive shaft passed the line on the housing, one revolution of the tire back to 12:00. Ok, the drive shaft passed the mark on the housing 3 times and almost another full turn= 3.55 etc etc. I hope I explained this well enough. Its a very good way to check when there is no other way other than pulling the cover. If the D/S went around 4 and a partial turn= 4.10. Hope this helps

 

thanks a lot for the help.

 

check underhood i.d tag should say, if stock diff.

 

I am trying to get an idea for what these truckshave on the average to help me with a "change" decision.
my truck has a 318 with auto,its 2wdand the 2.94 gears!!!!!
I need this truck to pulla 20ft trailer (from time to time)with contents will weigh no more 4800-5,000lbs.
The engine runs strong, but it will need a gear change. I know its no power house compared to a 440 but it should be fine.
I will not be changing the tires size much with the new wheels, tires and suspension thats in route so the overall gearing should not be effected.
I am thinking 3.73 or 4.10 gears. what do you guys like with the similar set ups and towing????

 

If it will be a daily driver 3.73 or 3.92 any higher will just eat up fuel if you are not running larger tires.
I am going 3.92.

 

Depends. What's your top speed now? Should be able to run 85-90 with stock tires (which are 235/75-15). 4.11's would be a 40% change, which will leave you redlining at 65 MPH. Fine if it's your off road vehicle that seldom sees highway use, but not so fun if you're actually getting on the interstate with it. 3.73 would be as steep as I'd go; at least then you can still keep up with freeway traffic.

 

MY 85 CAME WITH 2.94'S AND MY 88 HAS THE EVEN JANKIER 2.76s! BOTH 1/2 TONS...MOST OF THE MID TO LATE 80'S 1/2'S I HAVE SEEN IN BONE YARDS HAVE EITHER OF THESE .SOME OF THE ONES WITH OVERDRIVE TRANNY'S HAD 3.23's or 3.55 ...