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Fordboy300

Help?

Hey Guys, hope everyone is having a great Thanksgiving weekend anywho I have two questions.

First question is about my dads 86 f250. Okay so it has problem after my dad and I changed the rear brake shoes. It has a spongy pedal well it also had a brake booster okay today I changed the booster and re adjusted the rear brake shoes. The firmness of the brake pedal is okay but I feel like it could be better. Drove it and stepped on the brakes like a sudden brake and it stopped but not on the dime didnt even lock up the brakes or nothing.

Second question is about my 86 f150 so next year I plan on changing the rear gear I was reading up on and my mechanic mentioned that I would need to change the speedometer gear drive. Is there anyone that could help me find out which one is the right one I'm gonna need when I decide to do that.

"Big Red" 1986 Ford F150 XL

Ford 300 i6 4.9L .20 over bore(303 cubic inches now), p&p head, Crower 19212 cam, crower lifter spring kit, cloyes timing gears, EFI manifolds, Offenhauser C-series, Edelbrock 500cfm, DUI Ignition Dizzy, dual in single out magnaflow exhaust dumped before the rear axle.

Rembrant

Re: Help?

Fordboy300 wrote

Second question is about my 86 f150 so next year I plan on changing the rear gear I was reading up on and my mechanic mentioned that I would need to change the speedometer gear drive. Is there anyone that could help me find out which one is the right one I'm gonna need when I decide to do that.

What size tires are you running now? And are they the correct size for the truck?
What is your gearing now, and what gearing are you wanting to change to?

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

Ford F834

Re: Help?

Administrator

In reply to this post by Fordboy300

Sometimes on the brakes it takes a little while for the new pads/shoes to seat and wear to the imperfections of the rotor/drum. If the pedal firmness feels good and they are adjusted right then just try driving and braking for a bit and see if it improves. If you have spongy pedal that is usually air in the hydraulic system that needs bled out, but if you just did shoes and booster none of that should have been disturbed (did you take any lines off when you replaced the booster?).

On the driven gear, this web page may help 😉

http://www.garysgaragemahal.com/speedometer-driven-gears.html

SHORT BED 4-DOOR DIESEL: 1986 F350 4x4 under construction-- 7.3 IDIT ZF5+GVOD

STRAIGHT SIX 4X4: 1981 F150 2wd to 4x4-- 300 I6 close ratio diesel T19, hydroboost brakes, Saginaw steering

BIG F: 1995 F-Superduty under construction— converting to 6.9L IDI diesel ZF5+DNE2

Fordboy300

Re: Help?

In reply to this post by Rembrant

Well right I have two sets of tires. Both 15 inch wheels. P235 75R15 and P225 75R15. The original tire size for my truck is 215 75R15.

My gearing now is 3.08 open differential. I'm changing to a 3.55 Limited slip.

Fordboy300

Re: Help?

In reply to this post by Ford F834

I believe that's what happened. It must have air in the lines somewhere. Tomorrow my dad and I will bleed the brake. I will keep you guys posted.

Thanks !

Rembrant

Re: Help?

In reply to this post by Fordboy300

Fordboy300 wrote

Well right I have two sets of tires. Both 15 inch wheels. P235 75R15 and P225 75R15. The original tire size for my truck is 215 75R15.

My gearing now is 3.08 open differential. I'm changing to a 3.55 Limited slip.

Ok, if your truck has a 3.08 rear diff and originally had 215 75/R15 tires specified, then it should have a 8/18 speedometer gears. That's an 8 tooth drive gear, and an 18 tooth driven gear on the speedo cable.

If you install 3.55 gears and P225 75/R15 or P235 75R15 tires, you would have to install a 20 tooth driven gear on the speedo cable.

https://shop.broncograveyard.com/Speedo-driven-gear-20-teeth-black/productinfo/37192E/

This is just me doing some rough math here. One of the other guys may come along and correct me. I'm not sure if a 20 tooth driven gear will work with an 8 tooth drive gear. I know there is a range of gears that work with the 8 tooth drive gear, and in some case you may have to change the drive gear to get the correct ratio. All I can say is that the math calculates a 20 tooth driven gear.

Steve83

Re: Help?

Banned User

In reply to this post by Fordboy300

This caption contains Ford's instructions for correcting a speedo:

Brake problems usually come from the drums, because they're the least-understood & most-neglected. Click this & read the NEXT several captions:

Fordboy300

Re: Help?

Does it matter what transmission I have?

Because I have the SROD transmission I dont plan on changing it unless it grenades itself. I drive my truck pretty hard at times ever since I hopped the 300 up.

Ford F834

Re: Help?

Administrator

The tooth count of the drive gear inside the transmission or transfer case is the other half of the ratio equation. If you get a heavier transmission it may have a different drive gear tooth count. Often you can just correct it with the corresponding driven gear for your axle ratio and tire size.

Fordboy300

Update

Hi guys, So yesterday my dad and I bled the rear brake twice and today he drove it. He said he still felt a spongy/soft pedal he says it stops but it kinda takes its time.

Now I'm just assuming do you guys think it has anything to do with the power brake booster rod adjustment?? I did measure the old one to the new one (just with a engineers stick ruler) and its pretty close to old one.

Gary Lewis

Re: Update

Administrator

The rod between the booster and master doesn't change the feel. It just takes up the slack in the system. So, if you adjust it too small you'll have slack where the pedal will go down a ways before it hits the master cylinder's piston and braking starts. But from there the feel will be the same.

However, if you get it too long the brakes won't fully release. A friend of mine and I did just that and the brakes were apparently dragging some. As he drove the brakes got hot and expanded, causing more drag. And after about 20 miles they locked up.

So, you want to be on the shy side of the adjustment. But tomorrow I'll try to remember to find the true dimension from the factory shop manual and put it on the website.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Fordboy300

Re: Update

Thank you Gary, I would very much appreciate that!

Gary Lewis

Re: Update

Administrator

I've added the info to the Brakes page (Driveline/Brakes). Go to the Master Cyl's & Boosters tab and then the Push Rod Adjustment tab.

Hope that helps.

Gary, AKA "Gary fellow": Profile

Steve83

Re: Update

Banned User

In reply to this post by Fordboy300

Fordboy300 wrote

...still felt a spongy/soft pedal...
...do you guys think it has anything to do with the power brake booster rod adjustment?

No.

Gary Lewis wrote

I've added the info to the Brakes page...

Is it similar to this?

Gary Lewis

Re: Update

Administrator

Yup, probably identical.

Gary, AKA "Gary fellow": Profile