8rt Clutch

Fibber Mcgee

Fibber Mcgee

Well-known member
Does anyone know if there is more than one 10 inch pressure plate and clutch for a 48-53 F1.My clutch came apart so I put a spare clutch and plate in it to get home and had about 6 inches of travel in the pedal wit the linkage all the way out.I thought it was in the spare so I didn't worry about it until I replaced it with a new plate clutch and turned flywheel and still have about the same.I even replaced the linkage with a spare and still the same.It looks like ther is about 1 to 1 1/2 inches of travel in the throwout bearing and the plate does not have any adjustment I can see.What amI missing?
 
There are only two 10 inch clutch types available for the 8BA/8RT/8CM type engines and both are for a transmission with 1 3/8" spline input drive gear like the older center shift and remote control shift transmissions of the 30s & 40s. If you have the Long type 10 inch clutch plate (that has three groups of two even spaced bolt pattern) P/N 51A-7550-A with the 19A-7563-A pressure plate then the fingers in the PP are the only thing you can adjust and they have to be even. This Long type clutch could have been original to certain F1 pick ups depending on the type of transmission installed. The only other 10 inch that will work on the 8BA, 8RT, or 8CM type flywheels is the Mercury specific Borg & Beck type unit with the six evenly spaced bolt pattern. This one is only adjustable at reassembly of the PP during overhaul. If you have a good local clutch rebuilder, they can check the pressure plates out for you to make certain they meet limits for wear and have proper finger adjustment.

Either of these type clutch assemblies will work but they have to mach the flywheels they came with for bolt size and pattern.

Kerby
 
Have you got the old style throw out bearing & hub P/N 48-7561? This type was used from 1935 clear up to 1952 on pick ups. Also,do you have the old style clutch release mechanism that uses a lever on the equalizers shaft and rotates the clutch release shaft? If it was modified, I'd suspect it could have a car type bell housing with the fulcrum type clutch release mechanism. The 1953 F100s were different than any of the earlier F1 stuff.

I was also wondering if your transmission has a 1 inch 10-spline input drive shaft or the early type 1 3/8 inch 10-spline type? It makes a difference in that the smaller input usually used a 9 1/2 inch clutch and not a 10 inch. What year and model of truck is it?

Kerby
 
The clutch release shaft and bell housing should not affect anything as I have not changed them and they were working before, but I did change the throwout bearing ,I didnt know there was anything different about them.Is there any way the throwout bearing could make up for 1 1/2 inches of travel in the throwout bearing,they really didnt look that different.
 
I just wanted to know what you have so I can visualize it. There were three speed side shift, 3-speed top shift, and 4-speed top shift in several types then there was a 3-speed with overdrive in there somewhere. Most of them use the same clutch stuff but not all are the same in those years.

On the 48-52 3-speed top shift types, there should be about 1 1/2 inch of free play in the pedal pad from the top. At that point it should have the slack taken out of the throw out system and start pushing the clutch pressure plate fingers. If all dimensions are correct you will have full disengagement with the pedal all the way down. Full engagement with the pedal 1 1/2 inch from being all the way back up. If there is wear on the throw out hub, the throw out fork, or the pressure plate assembly components, you will likely have more free play than can be compensated for. Even worn out equalizer and throw out shaft bushings can cause some slack. When all added up or mixed with an incorrect component in there, you can have problems like this. I've even seen one where the throw out bearing was put in backwards but it didn't work very long before wrapping the little return spring around the hub a few times.
 
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It is a 3 speed topshift and the pressure plate is new the equalizer bushings seem good but now that you mention it I guess it it could be wear on the throwout hub or fork,I replaced the old throwout bearing with another one I had taken out of one of my other 3 speeds that seemed tighter but did not pay to much attention to where the fork rides.I can see in the clutch inspection cover and I guess Im just baffled by the throwout bearing having to move so far before it contacts the fingers.Thanks for the help.
 
Could you possibly have a broken pin/bolt that holds the fork9(that pushes the t/o brg) to the trans(clutch) shaft? Had that happen with a '39 trans to olds engine, 11" truck PP, 10 1/2" disc in my 32 in "61,
Paul in CT
 
That was a good thought about the pin,I just checked and it looks ok?I think I might reassemble the old parts and see what it looks like.
 
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