Hey Y'all. I am new here. Just picked up a 64 A100 Pick Up. This was a Navy truck from San Diego. The three-on-the-tree was replaced with an A904 but the rear gear is still a 3.91. This has got to go. The wheels and tires have been changed so that on the rear iare 215- 65R 15s . The Navy data plate says the vehical is supposed to be 77 inches tall, but now it is only 73.5". My question is, if this truck had come with an automatic, what gear ratio would it have had and what would the stock tire size have been? It has a 225 /6 with a holley 1 barrel carb. I am very excited about this project as the body is absolutely perfect. No dents and only three minor rust spots. The bed rails and tailgate are as straight as they come. Only has 72000 miles and runs and drives great. Thanks
5 posters
Rear Gear ratios and tire sizes
G-Man- Mayor
- Number of posts : 30743
Location : Fowlerville, MI
Age : 63
Registration date : 2008-05-06
- Post n°2
Re: Rear Gear ratios and tire sizes
Welcome to the site!!! When you get time give us some pic's of your "A"
wylee- Number of posts : 922
Location : middletown,ny
Registration date : 2009-04-03
- Post n°3
Re: Rear Gear ratios and tire sizes
the gears could be 2.76 for auto 3.23 crusing gears, 3.91 drag . and yes on the pics.....
Guest- Guest
- Post n°4
Re: Rear Gear ratios and tire sizes
Thanks guys...the pic I attached is of it as I got it.....filthy.....but I am glad to report it cleaned up very nice......I don't understand putting 215 tires on 10" wide rims?????the front tires are 195 - 70R 14......
I am legally blind but had eye surgery a week ago and hope to regain enough vision to drive it....but if not, I will have a ball fixing it up. Thanks
OK....let's see if this works
I am legally blind but had eye surgery a week ago and hope to regain enough vision to drive it....but if not, I will have a ball fixing it up. Thanks
OK....let's see if this works
G-Man- Mayor
- Number of posts : 30743
Location : Fowlerville, MI
Age : 63
Registration date : 2008-05-06
- Post n°7
Re: Rear Gear ratios and tire sizes
Looks pretty dam good dirty!!!!
Guest- Guest
- Post n°8
Re: Rear Gear ratios and tire sizes
Thanks G-Man....the bed wa full of leafs and when I cleaned it out, I found that the bed had only slight surface rust and not a dent in it anywhere......Ithe paint is a cheap overcoat over the original gray......but it waxed up nicely......the interior need a little work as the headliner is gone and the seats are torn........the steering wheel was replaced with a 20" Grant chrome GT style.......everything works.....I had to have the carb rebuilt and the fuel system cleaned and sealed as it had been sitting for 5 years in a guys backyard.......Anyome got a set of 3.21 geears they wanty to let go of....or better yet a sure grip......I got this for a song and the reason was that I swore I would not cut it up.......the owner was most emphatic on that......what I want to do is keep the current look and just perfect it......
Anyone bought a CD Service Manual from Faxon Auto Literature? I have seen them on EBAY and need to get something I can enlarge the text on.....
Thanks again
Anyone bought a CD Service Manual from Faxon Auto Literature? I have seen them on EBAY and need to get something I can enlarge the text on.....
Thanks again
jkr- Number of posts : 1148
Location : prince edward island canada
Age : 66
Registration date : 2008-05-29
- Post n°9
Re: Rear Gear ratios and tire sizes
i run 2:73's with a 727 auto and 360 and 215/60 14's. at 60 mph im doing about 1800 - 2000 rpm. a bit lazy getting away but cruises nice on the highway. go to a u-pick with old stuff and look for a dodge or chrysler car with an 8 3/4 rear end. they should have a ratio to fit your needs. it will be marked on the ring gear when you get it out or divide the number of pinion teeth into ring gear teeth. btw...nice truck chrome mirrors and grille too.
Guest- Guest
- Post n°10
Re: Rear Gear ratios and tire sizes
I thought the A100s had 7-1/4 rear ends?.....an 8-3/4 would be great as posi would be much easier to find....
The discoveries just continue.....I love the beginings of a project as you find all the things that went before......saw that I had McGard wheel lock on the mags and looked in the glove box to see (hope against hope) if the key was there....it wasn't and I was ready to get out the cheap sockets and sledge hammer.....but I saw that the batery cover was behind the passanger seat and there was a rag in it....under the rag was the key.......Thanks God.....this is the first time in my life I have bought a car/ truck with locks and had the key........
While in the glove box, I found an extra set of door locks but no key.....I will take them to a locksmith and have them re-loaded to fit my current key....Amazing
The discoveries just continue.....I love the beginings of a project as you find all the things that went before......saw that I had McGard wheel lock on the mags and looked in the glove box to see (hope against hope) if the key was there....it wasn't and I was ready to get out the cheap sockets and sledge hammer.....but I saw that the batery cover was behind the passanger seat and there was a rag in it....under the rag was the key.......Thanks God.....this is the first time in my life I have bought a car/ truck with locks and had the key........
While in the glove box, I found an extra set of door locks but no key.....I will take them to a locksmith and have them re-loaded to fit my current key....Amazing
jkr- Number of posts : 1148
Location : prince edward island canada
Age : 66
Registration date : 2008-05-29
- Post n°11
Re: Rear Gear ratios and tire sizes
look on the pinion snout and record the part number. the three common ones were- xoxo741 - xoxo742 - xoxo489. just concern yourself with the last three digits of the part number. 741 good 742 better 489 best. you can convert an open rear to posi with a powertrax unit and cheaper than buying and rebuilding a stock unit. if its used ( posi unit ) its probably worn the clutch cones down to nothing and not repairable.
Guest- Guest
- Post n°12
Re: Rear Gear ratios and tire sizes
Thanks JKR Ok after healing from eye surgery, the answer is 489.....what does that mean? The hogs head looks like an 8 3/4 but it seems weird to have a massive rear end like that in a little truck like this.....
jkr- Number of posts : 1148
Location : prince edward island canada
Age : 66
Registration date : 2008-05-29
- Post n°13
Re: Rear Gear ratios and tire sizes
best possible 8 3/4 rear gear out there. easiest to find different gear combos for and the largest bearings for reliability. i'll bet it's a posi unit too but they wear badly and the clutches are possibly slipping. the 489 case was more common in 1/2 tons and big chrysler wagons and such. old drag racers used them alot because they are virtually indestructible. it possibly was swapped out for another at some point in time. all three fit the rear housing. hang on to it ........jeff
Guest- Guest
- Post n°14
Re: Rear Gear ratios and tire sizes
Thanks Jeff......Have raced front engine dragsters for many years and many of my competitors used 8-3/4 rears....I always used 57-59 Olds or 9" ford rears.......not being a Chrysler guy until now, I had never really looked at an 8-3/4.......now that I can see a little better, it looks plenty stout......is there any outside indication for a posi unit?......any other numbers to look for?......
Being that this was a NAVY truck. there is a big brass plate on the dash with the gear spec.s and I jacked it up and calculated the rear ratio....it is 3.91 liike the plate says so I think this is the stock rear end.......
What size tires are you running?...the drive shaft angle on mine seems somewhat severe and yet the tires are only 215/65 x 15.......
Being that this was a NAVY truck. there is a big brass plate on the dash with the gear spec.s and I jacked it up and calculated the rear ratio....it is 3.91 liike the plate says so I think this is the stock rear end.......
What size tires are you running?...the drive shaft angle on mine seems somewhat severe and yet the tires are only 215/65 x 15.......
jkr- Number of posts : 1148
Location : prince edward island canada
Age : 66
Registration date : 2008-05-29
- Post n°15
Re: Rear Gear ratios and tire sizes
nothing else on them but jack up one side only and in neutral try to spin the wheel. of course you know the wheel won't spin if its a posi unit in "good " working order. i only run small tires 205/60/14 with 273 rear gear. the 360 is slow leaving but about 20 mpg on the highway crusing at 1800 - 1900 rpm. there isn't much difference between the old 318 and this engine in fuel economy but i save a ton on oil. as far as the shaft goes their so short the angle looks excessive but i have no problem. i do run the shortest extension housing at 8 inches and the slip joint style front u-joint. intermediate housing equals greater angle and ball and trunion are the worst.
oo3- Number of posts : 290
Location : new orleans
Registration date : 2008-06-01
- Post n°17
Re: Rear Gear ratios and tire sizes
i bought a faxon manual on disc - only complaint so far is it doesnt have a full wiring diagram - oo3
67a 100 pickup- Number of posts : 1319
Location : ann arbor, mi
Registration date : 2009-01-29
- Post n°18
Re: Rear Gear ratios and tire sizes
The color diagrams are on on ebay all the time, but you still need your manual for the wire gauge. It's not on the color ones, but they are laminated and don't get all funky and torn like the paper ones.
Guest- Guest
- Post n°19
Re: Rear Gear ratios and tire sizes
OK...I got the color, laminated Wiring diagram and the CD service manual....both very nice.....was able to determine stock tire size....but I still need to change the rear gear.....will all 8 3/4 ring gears fit all 8 3/4 housings or must I get one for my 489?....a friend gave me an 8 3/4 rear that we think has 3.23 gears but don't know yet what casting it is.....Thanks
67a 100 pickup- Number of posts : 1319
Location : ann arbor, mi
Registration date : 2009-01-29
- Post n°20
Re: Rear Gear ratios and tire sizes
Gear ratios available on the 8-3/4" axle through the years include: 2.76, 2.93, 3.23, 3.31, 3.55, 3.73, 3.91, 4.10, 4.56, 4.89, 5.17, 5.57. On OEM gear sets, the ratio is usually stamped on the ring gear edge. Ratio may be determined by the number of teeth on the ring gear divided by the number of teeth on the pinion gear or by counting the ratio of the number of turns of the pinion relative to one turn of the axle shaft. Do a search "chrysler 8 3/4 rearends" and look at the article with the same title. From reading through it the only htings that won't work together are sure-grip and non-sure-grip.
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