-66 truck ( C25 ) ??

parzimmerdahl · 10-31-2009, 05:45 AM

Can someone explain the difference between a model C20 and a a C25 chevy truck?

And how about the rear end, I have a "heavy duty" rear end with relieved axles on my -66 chevy truck C25. Is it easy to tell which rear end model it is?

see attachment.

Thanks for any replies!

bradrhale · 10-31-2009, 07:58 AM

cool FF you got there. should make for a durable truck.
there really is no difference in c20 and c25 except for year. they were both 3/4 ton 2wds.

parzimmerdahl · 10-31-2009, 01:55 PM

ok, thanks.

Does the rear end have a model name and is this one original for this truck?

..by the way, what did you mean by "FF"..

bradrhale · 10-31-2009, 02:55 PM

probably no model name knowing how old it is. you would be lucky just to find a gearing tag on it. you can take a pic of the cover though and get real close for an identification. also, look for a stamp on the front of the differential as some had an identifying stamp on them.
FF is a full floating rear end. basically means that the axle has no bearing in the axle tube. that big hunk of metal there has its own bearings, non sealed, and the axle attaches to the hub assembly. alot more dependable than the semi float.

leolkfrm · 10-31-2009, 03:07 PM

at 1 time i believe chevy used the even #'s and gmc used the odd's, but someone with older knowledge will have to confirm it

hotrodpc · 11-01-2009, 01:29 AM

I am not that old, but my experience had been that yes, the Chev used C10,20,30 and GMC used C15,C25 and C35. Back in those years, GMC usually was a leaf spring Dana 60 rear end, and the Chevy's were coil spring using a GM Corporate drop out 3rd member rear end, that pretty much the only 2 choices for gear ratio were 4.56 and 4.10. The 4.56 was more common, but I did find a 4.10 once in a junk yard from an old ambulance. Other than that one, all I ever seen was 4.56's. My dad had that rear end in his 68 C20, I had the Dana 60 in my 64 GMC C25. A pic of the pumpkin instead of the hub, I could probably tell if that is what it is by looking at it. You'll pretty much know if thats it by the drop out 3rd member.

hotrodpc · 11-01-2009, 01:33 AM

BTW, also, I have seen the leaf spring Dana 60 in Chevrolet too, if the truck had upgraded heavy duty suspension from the factory. Standard equipment on the GMC, optional upgrade on Chevrolet. Back then, there was a difference of GMC and Chev. Same today though too. GMC has better standard equipment, if you were to compare sticker for sticker.

leolkfrm · 11-01-2009, 07:02 AM

Quote:

Originally Posted by hotrodpc

I am not that old, but my experience had been that yes, the Chev used C10,20,30 and GMC used C15,C25 and C35. Back in those years, GMC usually was a leaf spring Dana 60 rear end, and the Chevy's were coil spring using a GM Corporate drop out 3rd member rear end, that pretty much the only 2 choices for gear ratio were 4.56 and 4.10. The 4.56 was more common, but I did find a 4.10 once in a junk yard from an old ambulance. Other than that one, all I ever seen was 4.56's. My dad had that rear end in his 68 C20, I had the Dana 60 in my 64 GMC C25. A pic of the pumpkin instead of the hub, I could probably tell if that is what it is by looking at it. You'll pretty much know if thats it by the drop out 3rd member.

old enough to remember it though!

hotrodpc · 11-01-2009, 08:08 AM

Both of my first trucks were older than me, and I worked on them both, so I say more experience than it is age. My first was a 62 C10, 2nd was a 64 C25. I don't need any help getting older Leo, the calendar does well enough as it is, then my daughter poppin out kids isn't helping either.

parzimmerdahl · 11-01-2009, 09:19 AM

Oooookey!
Hehehe, thanks guys for all!!

10-31-2009, 05:45 AM	#1
parzimmerdahl Full Member Join Date: Jul 2009 Location: Sweden Posts: 10	-66 truck ( C25 ) ?? Can someone explain the difference between a model C20 and a a C25 chevy truck? And how about the rear end, I have a "heavy duty" rear end with relieved axles on my -66 chevy truck C25. Is it easy to tell which rear end model it is? see attachment. Thanks for any replies! Attached Thumbnails

10-31-2009, 03:07 PM	#5
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 4,300	at 1 time i believe chevy used the even #'s and gmc used the odd's, but someone with older knowledge will have to confirm it __________________ 4 wheels move the body 2 wheels move the soul B.W.A.I

11-01-2009, 01:29 AM	#6
hotrodpc Senior Member Join Date: Jul 2008 Location: OKC, OK Posts: 3,149	I am not that old, but my experience had been that yes, the Chev used C10,20,30 and GMC used C15,C25 and C35. Back in those years, GMC usually was a leaf spring Dana 60 rear end, and the Chevy's were coil spring using a GM Corporate drop out 3rd member rear end, that pretty much the only 2 choices for gear ratio were 4.56 and 4.10. The 4.56 was more common, but I did find a 4.10 once in a junk yard from an old ambulance. Other than that one, all I ever seen was 4.56's. My dad had that rear end in his 68 C20, I had the Dana 60 in my 64 GMC C25. A pic of the pumpkin instead of the hub, I could probably tell if that is what it is by looking at it. You'll pretty much know if thats it by the drop out 3rd member. __________________ *Winners NEVER Quit , Quitters NEVER Win !!!*

11-01-2009, 01:33 AM	#7
hotrodpc Senior Member Join Date: Jul 2008 Location: OKC, OK Posts: 3,149	BTW, also, I have seen the leaf spring Dana 60 in Chevrolet too, if the truck had upgraded heavy duty suspension from the factory. Standard equipment on the GMC, optional upgrade on Chevrolet. Back then, there was a difference of GMC and Chev. Same today though too. GMC has better standard equipment, if you were to compare sticker for sticker. __________________ *Winners NEVER Quit , Quitters NEVER Win !!!*

11-01-2009, 08:08 AM	#9
hotrodpc Senior Member Join Date: Jul 2008 Location: OKC, OK Posts: 3,149	Both of my first trucks were older than me, and I worked on them both, so I say more experience than it is age. My first was a 62 C10, 2nd was a 64 C25. I don't need any help getting older Leo, the calendar does well enough as it is, then my daughter poppin out kids isn't helping either. __________________ *Winners NEVER Quit , Quitters NEVER Win !!!*

10-31-2009, 07:58 AM	#2
bradrhale Senior Moderator Join Date: Apr 2006 Location: Texas Posts: 8,025	cool FF you got there. should make for a durable truck. there really is no difference in c20 and c25 except for year. they were both 3/4 ton 2wds.

10-31-2009, 01:55 PM	#3
parzimmerdahl Full Member Join Date: Jul 2009 Location: Sweden Posts: 10	ok, thanks. Does the rear end have a model name and is this one original for this truck? ..by the way, what did you mean by "FF"..

10-31-2009, 02:55 PM	#4
bradrhale Senior Moderator Join Date: Apr 2006 Location: Texas Posts: 8,025	probably no model name knowing how old it is. you would be lucky just to find a gearing tag on it. you can take a pic of the cover though and get real close for an identification. also, look for a stamp on the front of the differential as some had an identifying stamp on them. FF is a full floating rear end. basically means that the axle has no bearing in the axle tube. that big hunk of metal there has its own bearings, non sealed, and the axle attaches to the hub assembly. alot more dependable than the semi float.

11-01-2009, 09:19 AM	#10
parzimmerdahl Full Member Join Date: Jul 2009 Location: Sweden Posts: 10	Oooookey! Hehehe, thanks guys for all!!

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