which rear could this be? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

454HO · 10-07-2008, 02:26 PM

Found an ad for a complete '78 Chevy truck rear end that supposedly has 3.55 gears. I've looked at the aftermarket gear makers and none of them have 3.55 for 10-bolt, 12-bolt or 14-bolt Chevy truck rear end housings. Was 3.55 a factory gear? What would be the most common housing it is in? What is the likelyhood it would have a posi carrier?

**Captkaos** · 10-07-2008, 04:29 PM

3.55 wasn't a factory gear ratio, if that is what you are asking about. On a 12bolt it is 3.42 and down and above 3.42 for the split. I have no idea what the 3.55 would fit, but I would assume it is has a spacer it would be for the 3.42 down and if not it would be 3.42 up.

Jonboy · 10-07-2008, 04:45 PM

If they really are 3.55 gears, it is probably a Ford rearend.

454HO · 10-07-2008, 08:09 PM

Well I sent the guy an email and tried calling the phone number posted in the ad. No response yet.

I did some more research and found that a 3.55 gear is common for both a 8.2" 10-bolt and a car 12-bolt. If this turns out to be a car 12-bolt, I'm definately snagging it. And yes, this is a common ratio for Ford 8.8" and Mopar 8.75" too.

10-07-2008, 02:26 PM	#1
454HO Registered User Join Date: Apr 2005 Location: Austin, TX Posts: 1,224	which rear could this be? Found an ad for a complete '78 Chevy truck rear end that supposedly has 3.55 gears. I've looked at the aftermarket gear makers and none of them have 3.55 for 10-bolt, 12-bolt or 14-bolt Chevy truck rear end housings. Was 3.55 a factory gear? What would be the most common housing it is in? What is the likelyhood it would have a posi carrier? __________________ - Greg

10-07-2008, 04:29 PM	#2
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: which rear could this be? 3.55 wasn't a factory gear ratio, if that is what you are asking about. On a 12bolt it is 3.42 and down and above 3.42 for the split. I have no idea what the 3.55 would fit, but I would assume it is has a spacer it would be for the 3.42 down and if not it would be 3.42 up. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

10-07-2008, 04:45 PM	#3
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Re: which rear could this be? If they really are 3.55 gears, it is probably a Ford rearend.

10-07-2008, 08:09 PM	#4
454HO Registered User Join Date: Apr 2005 Location: Austin, TX Posts: 1,224	Re: which rear could this be? Well I sent the guy an email and tried calling the phone number posted in the ad. No response yet. I did some more research and found that a 3.55 gear is common for both a 8.2" 10-bolt and a car 12-bolt. If this turns out to be a car 12-bolt, I'm definately snagging it. And yes, this is a common ratio for Ford 8.8" and Mopar 8.75" too. __________________ - Greg



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