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#1 |
Registered User
Join Date: Aug 2008
Location: Sanford, FLA
Posts: 170
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Upgrading rear end gear
Well considering I have the factory 3-speed in my 71. And I have never used 1st cuz it is such a low gear. And that 3rd tops out at around 65. I was considering going to a much higher gear ratio in the rear end so that it would bring first into a range of use and would up my mph in 3rd for interstate travel.
So my question is.... 1-Is this feasible to do? (Such as will it be worth the time and money?) 2-What is a good ratio to run with for my rear end as in how high can I go before it is a serious strain on the motor? 3-Will I need to change my chunk if I go with a ratio much higher than factory?
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1971 Chevy C10 LWB Shop Truck 1984 Chevy C30 Dually LWB Tow Pig 1985 Chevy K5 Blazer |
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#2 |
Love That '69
Join Date: Oct 2007
Location: Sherwood Park, Alberta, Canada
Posts: 360
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Re: Upgrading rear end gear
I know the feeling...My '69 has a stock 4.56 geared rear end. With my TH350/327 combo, on the highway at 70 MPH I'm reving around 4000 RPM's!! But nothing my 1000W stereo can't muffle...lol...I'll bet it would be worth the time/$ to do, I'd suggest maybe a 3.73 gear. For sure no higher than a 3.08 though!
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I AM CANADIAN!!!!! ![]() 1969 Chevy C/10 Truck - SBC V8, TH-350, 3.73 Posi, 1000W Rockford Fosgate Stereo System, B&M Megashifter, GT Grant Steering Wheel, Dual Magnaflow Exhaust System, Dynomax Headers, Lowered 1" Front & 3" Rear, Front/Rear Sway Bars, Racing Seats, 6000K HID Headlights 2008 Chevy Colorado LT - 3.7L I5, 4 Speed Automatic, Crew Cab, 4X4, Z71 Off-Road Package, "Ground Effects" Package, K&N Cold Air Intake, Supermod PTB, Magnaflow Exhaust w/ Resonator, 500W Kenwood / Rockford Fosgate Stereo System, Custom LED Lighting, 6000K HID Low's / High's, Blackcat Customs Gauges / Needles, Carbon Fiber Interior Accents, KrFabs 2" Lift Shackles / Torsion Bar Crank with Rancho RS5000 Shocks, Superskids Skid Plates Last edited by Classic69; 09-16-2008 at 09:53 AM. |
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#3 | |
Registered User
Join Date: Aug 2008
Location: Sanford, FLA
Posts: 170
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Re: Upgrading rear end gear
Quote:
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1971 Chevy C10 LWB Shop Truck 1984 Chevy C30 Dually LWB Tow Pig 1985 Chevy K5 Blazer |
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#4 |
Registered User
Join Date: Oct 2006
Location: Arizona
Posts: 835
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Re: Upgrading rear end gear
I agree with Classic 69, not sure how much freeway driving you do, but a 3.08 will run really well at freeway speeds, 3.42 a little less freeway friendly but will have more "get up" driving around.
Either way, if you buy a new gear set, it's going to be about 200 for that and figure another 250 or so to set it up. You can set the gears up yourself if you have the gauges along with plenty of time and patience as there is a lot of trial and error to get it right. I've done it but you have to remember that close enough doesn't work with gears.
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67 Short Step, 355, 700R 4.11 posi rear, 4/6 drop Discs on all 4 corners. Build thread: http://67-72chevytrucks.com/vboard/s...d.php?t=219094 Last edited by whatnow123; 09-16-2008 at 11:42 AM. |
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#5 | |
Registered User
Join Date: Aug 2008
Location: Sanford, FLA
Posts: 170
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Re: Upgrading rear end gear
Quote:
What info do I need to know in order to order the ring and pinion set? And if I go with a 3.08 for instance will I need to change the chunk due to the decreased diameter of the ring?
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1971 Chevy C10 LWB Shop Truck 1984 Chevy C30 Dually LWB Tow Pig 1985 Chevy K5 Blazer |
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#6 |
Registered User
![]() Join Date: Jan 2008
Location: Chesapeake Beach, MD
Posts: 812
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Re: Upgrading rear end gear
if your rear is all factory, i would replace the posi/center with a upgrade, get all new bearings/seals when you do the gears. better to do it 1 time JMHO
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71 cheyenne lwb 300rwhp best 1/4 time so far 12.8 @103 ![]() http://i195.photobucket.com/albums/z...en58/001-2.jpg |
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#7 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: Upgrading rear end gear
if you're going from something like a 4:11 or 4:56 up to a 3:08 highway gear there is no choice in the matter you must change the carrier or posi section out !!! like said you'd also be smart to change the bearings and the axel seals and plus the installition kit and the total parts bill will run in the $500-$750range with smart shopping to rebuild the rear
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#8 |
Senior Member
![]() Join Date: Aug 2008
Location: Cedar Park, Texas
Posts: 7,496
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Re: Upgrading rear end gear
My suggestion would be to find a factory 3.08 rear axle and swap it in. This is what I did for my dad's 71 GMC. (my avatar pic). We replaced the 3.73 rear with a 3.08 posi. With a 3.08 and the stock 250 I-6, it really slows the motor down on the highway. It would not be too good for towing, but the most he would ever pull anyway would be a 12 ft aluminum john boat. I am not sure on the exact break on your rear. What gear do you currently have? from your post, it sounds like a 3.73. I may be wrong, but I believe you could change the 3.73 to a 3.08 gear set without changing the carrier. However, you will soon find that even though you have a friend wiling to set up your new gears, by the time you buy all the parts, you are looking at big $$$. With my dad's, we tore the rear down and replaced the bearing seals and brakes. The ring gear and pinion were OK. I bought the axle for $100, and spent another $100 on parts, including cleaning supplies and paint. New gears alone are $200+
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#9 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Upgrading rear end gear
we'll have to assume you are talking about the 71 C/10 in the signiture?
We'll also assume that there is no optional gear listed on the SPID? Assuming the 2 things mentioned, and again, assuming it has not been swapped out, you should have a 3.73 in there already. If it "tops out at 65", you have other bigger issues to look at. You have a tach installed? You should be able to run over 100 MPH without topping out. Personally, I would locate another rear. Going from a 3.73 to a 3.08 would drop the RPMs pretty much to the ideal cruising (freeway speed) RPMs. However, you'll need to swap out carriers too. They aren't the same. I say locate a whole rear from the wrecking yard, or scanning the calssified section on here, and crack it open and inspect it. (as a spare rear, your truck won't be out of service for this part) If it checks out OK (and probably will) then you spend a day swapping out the rear axle at the cost of a couple U-bolts.... 30 bucks or less. |
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#10 | |
Registered User
Join Date: Aug 2008
Location: Sanford, FLA
Posts: 170
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Re: Upgrading rear end gear
Quote:
Yes it is a 71. I posted that in the original post for this topic. And No I did not see any specific gear option on the SPID. As far as swapping the axel out.... Thats about out of the question at this point. Here is the trucks build thread.... http://67-72chevytrucks.com/vboard/s...d.php?t=302785 I am simply looking to upgrade the center section and go with a higher ratio. I would like it to have a limited slip anyhow so that is a good time to do soo. And of course I would do the bearings and seals while it was apart. So my question is now... Where can I get the parts for my truck from at a reasonable price...?
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1971 Chevy C10 LWB Shop Truck 1984 Chevy C30 Dually LWB Tow Pig 1985 Chevy K5 Blazer |
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#11 | |
Registered User
![]() Join Date: Jan 2008
Location: Chesapeake Beach, MD
Posts: 812
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Re: Upgrading rear end gear
Quote:
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71 cheyenne lwb 300rwhp best 1/4 time so far 12.8 @103 ![]() http://i195.photobucket.com/albums/z...en58/001-2.jpg |
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#12 |
yard boy
Join Date: Sep 2007
Location: Franklin, TN
Posts: 119
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Re: Upgrading rear end gear
I just purchased a 3.73 ring and pinion plus master installation kit from Randy's Ring and Pinion. Total cost out the door was about $380 inc. tax. These are some of the most knowledgable guys around in dealing with rearends. Google the name and you won't be disappointed in their knowledge or service.
BTW, if you do drop below 3.73, then you will have to replace the carrier. Probably better to go junkin at that point! I wanted to go to 3.42, but I'm opting for a 700R4 swap out from the TH350 and staying with 3.73. Good Luck!
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1984 Chevy c20 |
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#13 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Upgrading rear end gear
You did say 71, but it would be a whole nother story if it was a C/20. So we need all the info before anyone can give good advice.
You should also probably make sure it is a 3.73 in there like it should be. |
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#14 |
sharp as a marble
![]() Join Date: Jan 2007
Location: atlantic beach,florida
Posts: 1,082
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Re: Upgrading rear end gear
I drove my 69 550 miles home the day I bought it. I knew it was turning some RPM's, but HEY, I wanted to get home. My truck was a 3 on the tree, with a 3.73 ( I pulled the cover ) and IMO that is too much gear. I have since added p/s, pdb, and a 700r4. I love the tranny change, and I dropped about 1000 RPM in high gear. I am going to go to a 3.08, or a 3.42 gear. I am looking for quiet, and about 1500 rpm at 65-70 MPH. There several sites you can go to and plug in your data, and it will give you an idea what the engine would turn at a specific speed. My truck now turns about 1600 RPM at 45-50 in in 4th with the converter locked. I love my truck
Last edited by cparman; 09-16-2008 at 08:13 PM. Reason: can't type |
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#15 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Upgrading rear end gear
a 3.07 gear with overdrive will more likely than not, kill your MPG. 3.73 to 3.42 is ideal (assuming a typical small block under the hood)
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#16 |
Registered User
![]() Join Date: May 2004
Location: La Crosse, WI
Posts: 29
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Re: Upgrading rear end gear
Staying on subject,I have a 70 C20 with the 456 gears.Coil springs and manual tranny.I can hardly run on the highway with it because I am afraid the 350 will blow apart if I go over 65 mph for too long.I would drive it more if it wasn't for that,what are my options in rear end swaps?
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#17 | |
Registered User
Join Date: Dec 2007
Location: Santa Maria, Ca.
Posts: 1,423
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Re: Upgrading rear end gear
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69 Chevy 4x4 383 Power ![]() |
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#18 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Upgrading rear end gear
direct swap, you have two choices...
eaton 4.10. Came in small block trucks with an auto, and I think small block/4 speed trucks. Dana 3.54 Came in big block/auto trucks. |
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#19 |
Registered User
Join Date: Aug 2008
Location: Sanford, FLA
Posts: 170
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Re: Upgrading rear end gear
Well my truck is as original as they come for the most part. The old man I got it from had it for 28 years. And he was the 2nd owner. He said the only thing he ever did was convert it from a column shift to a floor shift cuz his wife had a hard time shifting it prior.
It has the original 307 in it and the first owner upgraded from the 2 barrel to a larger single barrel. There is no upgraded gearing on the SPID. The only thing it states aside from cosmetic appearence is a heavier rear spring. That is all. So I assume that it is the factory rear end with factory internals. I chiseled off over and inch of grim off of the housing so I assume it has been a few years to say the lease since anyone has even looked at it. It is a C10. Not a 20. I do know that much soo... I guess I will just call a reproduction company and see what they say. Thanks for the info from the ones who helped
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1971 Chevy C10 LWB Shop Truck 1984 Chevy C30 Dually LWB Tow Pig 1985 Chevy K5 Blazer |
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#20 |
Senior Member
![]() Join Date: Aug 2008
Location: Cedar Park, Texas
Posts: 7,496
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Re: Upgrading rear end gear
We have more than one member asking for rear gear advice, so things are getting muddled.
Draginass: (C10) I still say shop around the board or your local yards and find a 3.08, inspect the stock gears, refurb it with new seals and bearings, add a Lock Rite from Powertrax ( I have one and like it because I can swap it into another rear axle if Iever want to without having to reset the rear.) Summit or Jeg's will fix you up if you are convinced that buying a new ring and pinion for your existing rear. as far as what carrier you need for the 3.08 gears, I had a 7.5" 10 bolt in my 79 Malibu when I first got it. It had 2.29 gears (!). I swapped in a set of 3.42 Richmond gears, since I was going to have to run the TH350 for a while before going to a 200 4r overdrive. They were "THICK" gears designed to make up for it being a 2 series carrier. I have since upgraded to the 2004r and an 8.5" rear with 3.73 gears out of a late 80's 442. (I had to add a posi to it, though, strangely enough, they were optional in Oldsmobiles. I bguess the 307 didn't need posi HAHA.) the P.O. had bought a stock posi but never added it. Buick GN's had an 8.5" rear, all were posi, but had 3.42 gears stock. I am getting of topic into my other passion. SORRY CPARMAN:How tall are the rear tires you are running? I would not advise going lower than a 3.42 rear gear with a 700r4 overdrive and 30" tires (taller tires would make it even worse). Changing from 3.73 to 3.43 is not worth the expense , IMO. Unless you have a Big Block with a lot of torque, You are also going to experience the trans shifting in and out of overdrive anytime you try to pull a slight grade. ANNOYING and it will eventually burn out your trans.! |
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