OK so I figured out the rear end in my 56 T-Bird has been changed to what I think is a 9" Ford passenger car. It has a 3.70 ratio according to the tag. Which makes sense as my speedometer reads way high. From what I have read to work in a T-Bird you need to use lowering blocks with the passenger car rear, which my car already has. Also what I have read, they either have 31 spline axels or 28 spline. Is there anyway to tell which I have without removing one? I need to change it to a 3.30 ratio, to get better hi way speed, and there is no speedometer gear for my auto trans for the 3.70. So I think I should look for a pumpkin with a 3.30 ratio. Thoughts? Comments. ratio. What cars and years can I get a pumpkin with the 3.30 ratio from?
what are you using for an engine? a 3.70:1 gear is not a bad gear. Granted it is not as tall as a 3.30 but it still is not a bad gear. Why not just find a speedometer adjuster. They are not that expensive and pretty easy to install.
Not absolute but usually the hub end on 31 spline axles are solid with two small holes and 28's are dished.
Just change the gears, the 9" is one of the easiest to set up, or hire someone to do it. All the stock type gears interchange. But make sure what ratio you have first. I do so by jacking up one side and turning one tire two revolutions, while counting the number of turns of the driveshaft. (if it has a limited slip differential, then turn both tires one turn each instead).
Figure out the spline count. 3:25s we’re common. Gears ain’t too bad to change 3:70 is perfect with an OD
I have tons of ring gear sets , there are tons of already set up gear sets . Don’t know what you plan using your car for , but 28 spline are find for daily driver , open no LDS is fine also . Before spending lots of $$ swap to 8.8 Ranger
The car is a stock 56 Thunderbird with a 312 and stock automatic. The rear end has a wine in it so it needs work anyways. Now to find the correct pumpkin with a ratio close to 3.30.
What is the 1st gear ratio? It may be a little doggy off the line with the 3.25 gear. If you can live with it, great. What ratios were available from the factory? The 3.56 was popular with stick Fairlanes and Galaxies.
so the 66 truck rear i have with 3:70 that i wanna use with 700r4 should be good? just wanna a cruiser
Be glad you’ve got the 9”, the Dana’s are kind of a PITA these days. I’ve run 3.3’s behind Fordo’s, and from 3.3’s to 4.27’s in my bird behind a variety of transmissions. The 3.3’s are a good choice for your set up. But if you want to leave quickly you’ll be pulling the Fordo down into first from a stop. All ok, that’s how they were designed. Don’t be surprised if the speedo is still off. I’ve always suspected Ford just changed the speedo face from 120 to 150 on the birds to make you think they were faster than they are.
I have never seen a 9" axle like the one on the right, only 8". That one can be used in a small bearing 9" housing, but you need to have the backing plate and drum to match.
You need to pull the axle and count the splines. Speculate all you want, but only pulling the axle will tell you for sure. Most likely its a 28 spline as they were more common. Your 3:70 ratio is worth way more than a 3:25, even if it whines a little. 3.25 should be fairly easy to find, but you will probably see more around the 3.00 or 3:10, so you need to count the gear teeth to be sure rather than just rotating the pinion. Also be sure you aren't looking at a 9.375 pumpkin from a Lincoln. Looks very similar and usually 2.7 to 2.5 ratio.
If you do find another pumpkin, make sure it has the same u joint yoke that you have now. Looks like the pickup truck version. 1330 joint and it's longer than some of the others. so much easier to find the only the gears you want, and keep the rest of the stuff you have. Really. Seriously.
@squirrel says it easy, and yes it is because I set up a 9inch. It can all be done on a bench. Other advantage is you’re only buying a gear set, as opposed to spending more for a unit. And you would still check the contact pattern before installing it anyways and the preload on the pinion. Even if I bought a complete unit from a Currie, quick performance, etc, I’d still check it out first.
In my Ford endeavors, 3:90, 3:70, 3:50, 3:25, and 3:00 have been the most common ratios Ive seen with trucks. 2:75s we’re common swaps from cars. (Probably a truck option as well) The 3:90 and 3:70s were common in 60s 6cyl trucks. The 31 spline was common in 70s trucks and had a beefed up housings. 28 spline has been the most common for late 50s to early 70s car and truck from my experience. Every now and then a modular housing posi turns up.
I have had 2.69's that came in 59 Ford Pass. There was a 2.91, 3.10, 3.25, 3.50, 3.56, 3.70, 3.89, 4.11, 4.30, 4.57, 4.86.
Me either. I didn't notice the writing on the axle until you mentioned it. All I've seen are the solid drum register variety like on the left.
We used to find steeper ratios in old Econoline vans. Like a 4.11 or 4.30, likely all those are gone from most 'yards. I went with a 1310 yoke on mine, a mistake. But that is what I had with the OG rear when I had the driveshaft made up. I tend to avoid holeshots.
Although Ford had a 3.31 gearset listed, I would have no idea what car it came in and that ratio is not listed in any of the aftermarket guys. Closest set as stated is 3.25, which was used in a lot of the performance cars of the late 60s and early 70s, as well as two-wheel drive pickups. 4-wheel drive used 3.50 usually.
The Jalopy Journal
