9 inch posi?
Thread Starter
|
Freshman User
Joined: Sep 2017
Posts: 29
Likes: 0
From: Francis
9 inch posi?
My 79 f150 rwd has a real hard time hooking up. Way too easy to spin.....a tire! As truck sits, with crappy tires, it with spin when I hammer throttle from about 10 MPH. Although fun, I'm more interested in g-forcing me against the seat leaving a stop light, rather than having a smoke show. It's been a long time since I've driven one of these trucks, but I'm sure the truck I had before, in 1982, hooked up better than this one. I know it needs decent tires, and that good tires would help alot, but,
1st question is, what's the best, easiest, and cheapest way to put a posi in? What vehicles came out with them that I can look for at the wreckers?
2nd question is, suspension geometry is not my thing. Is there something I need to look at, or do there that will allow the truck to launch better?
1st question is, what's the best, easiest, and cheapest way to put a posi in? What vehicles came out with them that I can look for at the wreckers?
2nd question is, suspension geometry is not my thing. Is there something I need to look at, or do there that will allow the truck to launch better?
Thread Starter
|
Freshman User
Joined: Sep 2017
Posts: 29
Likes: 0
From: Francis
Lol! I see that! Just read your post. Already some good info!
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
As for the "hooking up" at launch, trucks are pretty light in the butt. I've never hot rodded a pick up but I've had a couple of quick heavy cars. The old flapper bars worked pretty good for me. Caltrac suspension might be something to look at too
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
If you're going to order a new center section, you'll need to know a few things before calling. Desired gear ratio, universal joint size, yoke length, and type differential you want.
If you're wanting to change ratio in order to hit a specific RPM at a specific MPH, there's a formula that helps: MPH x 336 x gear ratio / tire diameter = RPM. If you're running an auto transmission without a lock-up converter you'll need to add about 5% at cruise speed.
If you're wanting to change ratio in order to hit a specific RPM at a specific MPH, there's a formula that helps: MPH x 336 x gear ratio / tire diameter = RPM. If you're running an auto transmission without a lock-up converter you'll need to add about 5% at cruise speed.
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
Ahhhhh, yes true. Spline Count! Thanks for correcting me.
Grandpa, if this seems intimidating, don't sweat it. It's not. You can get your gear ratio from the door tag. You can measure the universal joint caps and yoke length. As for spline count, the only way I know to get that is to pull one axle shaft and count the splines. It's pretty easy but be prepared for the axle bearing to come apart. I would never put an old bearing / seal unit back in there anyway.
Grandpa, if this seems intimidating, don't sweat it. It's not. You can get your gear ratio from the door tag. You can measure the universal joint caps and yoke length. As for spline count, the only way I know to get that is to pull one axle shaft and count the splines. It's pretty easy but be prepared for the axle bearing to come apart. I would never put an old bearing / seal unit back in there anyway.
Trending Topics
Thread Starter
|
Freshman User
Joined: Sep 2017
Posts: 29
Likes: 0
From: Francis
Ahhhhh, yes true. Spline Count! Thanks for correcting me.
Grandpa, if this seems intimidating, don't sweat it. It's not. You can get your gear ratio from the door tag. You can measure the universal joint caps and yoke length. As for spline count, the only way I know to get that is to pull one axle shaft and count the splines. It's pretty easy but be prepared for the axle bearing to come apart. I would never put an old bearing / seal unit back in there anyway.
Grandpa, if this seems intimidating, don't sweat it. It's not. You can get your gear ratio from the door tag. You can measure the universal joint caps and yoke length. As for spline count, the only way I know to get that is to pull one axle shaft and count the splines. It's pretty easy but be prepared for the axle bearing to come apart. I would never put an old bearing / seal unit back in there anyway.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
Yeah a tach is handy for more than just entertainment. I need to install one too. In a pinch you can use your timing gun to confirm RPM while driving. I did it to confirm gear ratio before I ordered center section. Something else on the spline count....axle shafts are not overly expensive. If it was me, I'd replace them too. In which case, it doesn't matter what's in there now. Just order 31's. That's what I did.
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
I never thought of that. I wonder if that'd work? I no longer have any open diff vehicles to try that out.
I had a diff / trans guy explain to me why an open diff won't reveal it's gear ratio that way. I didn't understand all of it, and I can't convey it, but I understood enough. But of course I had to try it anyway. Didn't work.
I had a diff / trans guy explain to me why an open diff won't reveal it's gear ratio that way. I didn't understand all of it, and I can't convey it, but I understood enough. But of course I had to try it anyway. Didn't work.
Thread Starter
|
Freshman User
Joined: Sep 2017
Posts: 29
Likes: 0
From: Francis
I was told that with an open diff, one tire stays on ground. Turn lifted tire one revolution, while counting driveshaft turns. Divide driveshaft turns in half, and use that number to determine ratio. I've never done it though.