Lowering the rear question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

steves1967 · 08-29-2010, 06:06 PM

I looked thru the search engine but could'nt find any info. How much can I safely lower the rear of my truck before I get into trouble with the 2-piece driveshaft? It's a 71 c20 longbed. I'd like to drop it 4-5 inches. I will be getting new rear springs made but I'm concerned about the bearing support for the driveline- I really dont want any vibrations..
Thanks for the help!

swierker · 08-29-2010, 07:17 PM

I have a long bed too and I just bought 5" rear drop springs for my truck. I got my stuff at Early Classic and asked the same question. They told me that at dropping a truck actually improves the pinion angle from stock and that from the factory it was not ideal. I trust them because they specialize in only these trucks. I have not installed the springs yet so I can't verify for sure, I'm only letting you know what I was told. Actually I think I asked the same question from CPP and they said no pinion angle correction was necessary.

Alex Hayley · 08-29-2010, 07:52 PM

I dropped my 72 1/2 by 4" in the rear and have no problems.

ChevLoRay · 08-29-2010, 09:48 PM

Mine is dropped 4 inches in the rear, though it is a SWB. Still, it has a 2-pc drive shaft. I did install the upper shock mount relocators that help to restore the correct shock angle, so that is something to consider. I have ECE components on my truck.

This is assuming you have a coil-sprung rear end. If you have leaf springs, there may be some differences to contend with.

Check out www.earlyclassic.com. But, there are also vendors on here who also sell what you are asking about.

steves1967 · 08-29-2010, 10:58 PM

Thanks guys, yes it has leaf springs. A local shop here said they can build me a new set of springs with the same weight rating. I just need to give them one of my old springs and tell them how much lower I want the truck to sit.

usmcchevy · 08-29-2010, 11:46 PM

You could flip the rear axle above the springs. Might be cheaper than having new springs made

steves1967 · 08-30-2010, 01:45 AM

With all the towing and hauling I do, I'd rather just get new springs made- besides it's only $220 for the set of new springs. Thanks!!

08-29-2010, 06:06 PM	#1
steves1967 Registered User Join Date: Dec 2001 Location: Manteca, Ca USA Posts: 305	Lowering the rear question I looked thru the search engine but could'nt find any info. How much can I safely lower the rear of my truck before I get into trouble with the 2-piece driveshaft? It's a 71 c20 longbed. I'd like to drop it 4-5 inches. I will be getting new rear springs made but I'm concerned about the bearing support for the driveline- I really dont want any vibrations.. Thanks for the help! __________________ '71 Chevy 3/4 Ton Longbed '22 Chevy Tahoe RST '67 Firebird- 8 sec street car '24 GMC CC 4x4 Duramax Dually

08-29-2010, 07:17 PM	#2
swierker Registered User Join Date: May 2010 Location: Wallingford, PA Posts: 186	Re: Lowering the rear question I have a long bed too and I just bought 5" rear drop springs for my truck. I got my stuff at Early Classic and asked the same question. They told me that at dropping a truck actually improves the pinion angle from stock and that from the factory it was not ideal. I trust them because they specialize in only these trucks. I have not installed the springs yet so I can't verify for sure, I'm only letting you know what I was told. Actually I think I asked the same question from CPP and they said no pinion angle correction was necessary. __________________ 1970 Chevy LWB - 305/350 In Progress: 4/6 ECE drop, front discs, power brakes, Coys C5's. Last edited by swierker; 08-29-2010 at 07:18 PM.

08-29-2010, 07:52 PM	#3
Alex Hayley Registered User Join Date: Jul 2000 Location: NC Posts: 987	Re: Lowering the rear question I dropped my 72 1/2 by 4" in the rear and have no problems.

08-29-2010, 09:48 PM	#4
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Re: Lowering the rear question Mine is dropped 4 inches in the rear, though it is a SWB. Still, it has a 2-pc drive shaft. I did install the upper shock mount relocators that help to restore the correct shock angle, so that is something to consider. I have ECE components on my truck. This is assuming you have a coil-sprung rear end. If you have leaf springs, there may be some differences to contend with. Check out www.earlyclassic.com. But, there are also vendors on here who also sell what you are asking about. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

08-29-2010, 10:58 PM	#5
steves1967 Registered User Join Date: Dec 2001 Location: Manteca, Ca USA Posts: 305	Re: Lowering the rear question Thanks guys, yes it has leaf springs. A local shop here said they can build me a new set of springs with the same weight rating. I just need to give them one of my old springs and tell them how much lower I want the truck to sit. __________________ '71 Chevy 3/4 Ton Longbed '22 Chevy Tahoe RST '67 Firebird- 8 sec street car '24 GMC CC 4x4 Duramax Dually

08-29-2010, 11:46 PM	#6
usmcchevy Has more rust than truck... Join Date: Apr 2005 Location: Ivanhoe, MN Posts: 2,421	Re: Lowering the rear question You could flip the rear axle above the springs. Might be cheaper than having new springs made __________________ 1972 Custom/10 SWB, 4.8/4l80e Build thread LSx Swap FAQ index

08-30-2010, 01:45 AM	#7
steves1967 Registered User Join Date: Dec 2001 Location: Manteca, Ca USA Posts: 305	Re: Lowering the rear question With all the towing and hauling I do, I'd rather just get new springs made- besides it's only $220 for the set of new springs. Thanks!! __________________ '71 Chevy 3/4 Ton Longbed '22 Chevy Tahoe RST '67 Firebird- 8 sec street car '24 GMC CC 4x4 Duramax Dually



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.