I have a question for you folks. I'm rebuilding a 1977 Ford F-150 short box and I picked up a different cab for the truck, It is a 76 Cab 2-wheel drive is the Brake Power Booster different than a 77 model that is a 4-wheel drive because the bolt pattern is different where it bolts up to the cab of the truck. The 77 is a bigger pattern than the other one, if you need more info will b back later to see
Thanks again folks

 

Well ... if they're different sizes and have different bolt patterns, then I'd say that yes, they're different. But you already knew that ...

 

1973/79 F100/350: There are 22 different brake pedals, 19 different master cylinders, 17 different P/B boosters, 7 different clutch pedals, I kid you not!

Differences: Manual vs. power brakes; 2WD vs. 4WD; specific years; before/from specific serial numbers; with/without speed control.

Whatever booster is used...it must match the correct brake pedal.

 

I swapped in a t-18 in place of an automatic behind a 460. Had to change the pedal set. After much research, this is what I ended up doing to make the booster work with the pedal set I bought on eBay.

 

Hey Alex2265 what year is your cab that u redid the brake pedal and boostrer on, tks for the pictures also
NumberDummy & Alex2265 the mounting holes on the cab I have now are 3 1/4 across and 2 1/8 up and down the mounting holes on the 77 are 3 3/4 across and 3 1/2 up and down Alex did u redrill the holes or get the right booster and then redue the rod in the back gonna new some info to do mine also tks plus will be looking around the internet for help also but there is a ton on this site which is great

 

The year of my cab is 79. As ND may have mentioned and the LMC catalogue shows, you have to go by vehicle characteristics and serial number. For mine, the truck came after the break in serial numbers. So, I knew based on the 2wd, power brake dual piston caliper, that it was 1 of 2 boosters. Now, your cab may be set up for the earlier style. On mine, there is a bracket that the booster bolts to and this bolts to the cab. I can't measure it, but the bracket bolts via 4 of the pedal bracket bolts. The firewall side bolt pattern is smaller than the booster side. My style booster is the direct acting style. However, some of the older ones in the 70s used a bell crank type acting style to multiply force. These differences may account for your issue. I found many lengthening kits for GM, but none for ford. My solution may not apply to you since I matched my booster to what was in the truck and simply lengthened it.

 

As you can see and ND indicated, there are at least 350 different possible combinations for 73-79 trucks.


The bracket I have is closest to the upper left image.

 

Based on what you said, I'd match the master cylinder and booster to your cab. Re-drilling the holes sounds dangerous since you may not be able to mount your pedal bracket then.

 

I have a single diaphragm brake booster from a '68 F250, a single diaphragm brake booster from a '74 F100, a single diaphragm high-mount bell crank booster from a '78/'79 F150, a dual diaphragm booster from a '74 F350 and a dual diaphragm booster from a '75 F350.

The stud spacing on the back of all these boosters measures 3-3/4" horizontally and 3-7/16" vertically.

The booster-to-firewall bracket hole spacing is 3-1/8" horizontally and 2-1/8" vertically.

The booster-to-MC stud spacing is 3-3/8".


The only booster I have in the above listed group, with an adjustable input rod, is the one from the '68 F250. The '78/'79 bell crank style booster I have has a flat input rod, which to my knowledge, is longer than the flat input rod on '77-earlier versions of the bell crank boosters.

The other remaining boosters I have have fixed length (circular) input rods with rounded eyelets on the tip (eyelets with a triangular tip indicates a booster for use with cruise control).

I don't have a 4WD truck and I've never looked at a booster in one but, it doesn't seem logical that the firewall-to-bracket hole spacing would have been different from a 2WD. --if you're trying to mount the booster straight to the firewall without the brackets, that may explain why the studs are wider spaced.

Some photos of the two boosters in question would probably help clarify what's going on with your setup.

 

Thanks for the help guys saw some of the pictures posted here and on the internet and went looking and found everything I needed, had to have that adapter put on first then the booster bolted to that. That's what happens when u take it apart 3yrs ago and just starting to put it together now but we got it all back where it should b so thanks again.
If it wasn't for this site I don't know what I would do keep up the good work folks!!