7.5" vs 8.8" drum brake compatibility

philcore3 · Sep 22, 2023

I have an 85 which i am restoring, I debated back and forth between keeping the 7.5" axle or swapping out to an 8.8". In the end, due to budget and simplicity I decided to keep the 7.5 for now. My question is, when shopping for new backing plates, are the 7.5 and the 8.8 the same part? I already verified that my new axles and drums fit 79-93 so I'm 75% sure that back plates are the same but want to make sure. Thanks!

philcore3 · Sep 22, 2023

302, v8 manual 2.73 gears if that matters

philcore3 · Sep 22, 2023

philcore3 said:
302, v8 manual 2.73 gears if that matters. I am assuming i had 9" drums and the fox resto kit https://lmr.com/item/LRS-1126K/79-93-Mustang-5-Lug-Rear-28-Spline-Axle-Drum-Kit is 10" drums, so I'm concerned there will be a discrepancy of an inch.

limp · Sep 22, 2023

My understanding is they are different and UNAVAILABLE..... I have had offers for the backing plates from my 7.5 I removed who have told me this....

limp · Sep 22, 2023

philcore3 said:
I already verified that my new axles and drums fit 79-93 so I'm 75% sure that back plates are the same but want to make sure. Thanks!

I can understand reusing a 7.5" but I question putting any money into one......

philcore3 · Sep 22, 2023

limp said:
I can understand reusing a 7.5" but I question putting any money into one......

I am reusing it. If I upgrade to an 8.8 the axles will swap over as well.

LILCBRA · Sep 22, 2023

I know that the brakes from a 7.5 from an 84 V6 car will swap onto an 8.8. I did this when I swapped the 84's drivetrain with that of a Mark VII.

limp · Sep 22, 2023

philcore3 said:
I am reusing it. If I upgrade to an 8.8 the axles will swap over as well.

Good point.. I take back my comment...LOL....

FoxChasis · Sep 22, 2023

All of the drum brake components are the same between 7.5" and 8.8", on the Mustang...backing plate, drum, shoes, wheel cylinders, etc.

10" rear drum brakes were OE on V8 LTD/Marquis, and maybe Fairmont/Zephyr wagon? (I don't remember exactly other than LTD/Marquis.) They were not ever on Capri/Mustang so that LRS kit is an 'upgrade' and would require parts in that kit (larger diameter backing plates, large diameter drums, large shoes, etc.).

nickyb · Sep 22, 2023

I did the cobra brake upgrade and have the backing plates and e brake cables . Lmk.

limp · Sep 22, 2023

FoxChasis said:
All of the drum brake components are the same between 7.5" and 8.8", on the Mustang...backing plate, drum, shoes, wheel cylinders, etc.

10" rear drum brakes were OE on V8 LTD/Marquis, and maybe Fairmont/Zephyr wagon? (I don't remember exactly other than LTD/Marquis.) They were not ever on Capri/Mustang so that LRS kit is an 'upgrade' and would require parts in that kit (larger diameter backing plates, large diameter drums, large shoes, etc.).

Don't some of the 7.5" come with 9" drums?

85GTStangGuy · Sep 22, 2023

limp said:
Don't some of the 7.5" come with 9" drums?

They all did. Same as all the 8.8s... 9" drums also. That's what FoxChasis is saying.... that the 10 inchers were only on V8 LTD's and Marquis' (and maybe F/Z's).... never on Stangs or Capris.

FoxChasis said:
10" rear drum brakes were OE on V8 LTD/Marquis, and maybe Fairmont/Zephyr wagon? (I don't remember exactly other than LTD/Marquis.) They were not ever on Capri/Mustang so that LRS kit is an 'upgrade' and would require parts in that kit (larger diameter backing plates, large diameter drums, large shoes, etc.).

Rcdgl · Sep 23, 2023

I have used 82 rear 7.5 brakes on both 7.5 and 8.8 axles. I usually remove the axles, unbolt the backing plates, leave the lines connected and just put it all back. May have to tinker with the axle vent and hard line, but easy.

limp · Sep 23, 2023

85GTStangGuy said:
They all did. Same as all the 8.8s... 9" drums also. That's what FoxChasis is saying.... that the 10 inchers were only on V8 LTD's and Marquis' (and maybe F/Z's).... never on Stangs or Capris.

So if you have 9" 7.5 backing plates and you are running 10" drums, will the smaller backing plates work??

85GTStangGuy · Sep 23, 2023

I don't actually know myself, but I'd assume not. I would think the wheel cylinders, brake shoes and the shoe contact points would all be further out radially, necessitating the larger diameter backing plates.

FoxChasis · Sep 23, 2023

No, you cannot use 10" drums with 9" backing plates. You either use all 9" parts or you use all 10" parts.

Mustang5L5 · Sep 25, 2023

85GTStangGuy said:
They all did. Same as all the 8.8s... 9" drums also. That's what FoxChasis is saying.... that the 10 inchers were only on V8 LTD's and Marquis' (and maybe F/Z's).... never on Stangs or Capris.

I think Rangers got the 10" drums as well.

But my understanding was the same about the 7.5" and 8.8 drums. They are the same 9" units. Even the axle shafts are the same. You could take a 7,5" with drum brakes and swap them onto an 8.8 housing and use everything.

EDIT: However, i typically think of 86+ when I say this. The early 4-eye cars got some weird parts. There were aluminum drums, 9" front brakes, and even a 6.75" sterling axle. There was even a weird German 5-spd trans that nobody knows about.

FoxChasis · Sep 25, 2023

Aluminum drums were on early (before 1983) turbo cars. If they happened to make it onto turbo cars before 1983, so be it. Same years for 9" front disc and 6.75" rear axle .. but they were for non-V8 and non-turbo cars.

The 5-speed, which was NOT a T-5, was made by Tremec in Mexico, and dated back to late 1980 model year and went through the end of 1983 model year. (So there were TWO 5-speeds in model year 1983 but almost no one knows about the Tremec 140VS 5-speed). The German transmission was a 4-speed and was used through 1986.
Fox Capri/Mustang manual transmissions:
Ford of Germany (FoG) nnET 4-speed (trans tag "78ET" or "83ET" and "FOG", door tag "7")
Borg Warner 4-speed (trans tag "RAD", door tag "6")
Tremec SROD 4-speed overdrive (trans tag "RUG", door tag "5" 1979 and "4" 1980-83)
Tremec 140VS 5-speed overdrive (trans tag "RAP", door tag "5")
Borg Warner T-5 5-speed overdrive (trans tag "13-52", door tag "2") --- Borg Warner sold manual transmission division to Tremec in 1998

Mustang5L5 · Sep 25, 2023

Ah. I confused those. The German "ET" 4-spd from the pinto.

The other 5-spd had a non-standard shift pattern if i remember correctly. I think i've seen it only once.

FoxChasis · Sep 25, 2023

The Tremec 140VS 5-speed OD...

7.5" vs 8.8" drum brake compatibility

philcore3

philcore3

philcore3

limp

wrap a little cheese around it and its a done

limp

wrap a little cheese around it and its a done

philcore3

LILCBRA

I wish I didn't have all of these balls in the air

limp

wrap a little cheese around it and its a done

FoxChasis

nickyb

I gotta say i never painted my nuts, Never Ever

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limp

wrap a little cheese around it and its a done

85GTStangGuy

Rcdgl

limp

wrap a little cheese around it and its a done

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FoxChasis

Mustang5L5

That is…until I whipped out my Bissell

FoxChasis

Mustang5L5

That is…until I whipped out my Bissell

FoxChasis

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7.5" vs 8.8" drum brake compatibility

wrap a little cheese around it and its a done

wrap a little cheese around it and its a done

I wish I didn't have all of these balls in the air

wrap a little cheese around it and its a done

I gotta say i never painted my nuts, Never Ever

Attachments

wrap a little cheese around it and its a done

wrap a little cheese around it and its a done

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

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