What rear end gears should I get? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Rc 415 · 09-10-2007, 10:19 PM

I've got a 30" tall tire in the back now, and I'm running 2.73 gears with an auto 700R4, I want to accelerate quick, but I'm not sure about what all gears are good for what in the rear, all I know is I am not happy with the rear gears in there now, I cant even chirp the tires, and the truck just doesn't accelerate quick at all, even on the freeway!

slugish · 09-10-2007, 10:48 PM

with a 7004r with 30 in. tires , run at least a 3.73 rear end . should be perfect for what you want. you definitely will do some serious chirping with a 3.73, plus it will be very cruisable. best of both worlds.

xtreme80 · 09-11-2007, 01:26 AM

Since you got an overdrive you could even go a little higher than 3.73 if you wanted, but that would probably be the best gear for your ride. Lucky you with overdrive, I'm doing a 3.73 on a 3 speed tranny... haha

Tink · 09-11-2007, 08:40 AM

Got 3.73s, 30s and a 700r4 on the 85. She will chirp a tire and pull like a frieght train on the highway. Turns about 2400rpm at 70mph.

Rc 415 · 09-11-2007, 12:37 PM

Will this rearend work in my truck? its from a 1990 chevy
http://sfbay.craigslist.org/eby/pts/419084926.html

Rc 415 · 09-12-2007, 03:08 PM

up

jchav62 · 09-12-2007, 03:40 PM

I agree, 3.73's....Especially with an over drive tranny..

454HO · 09-12-2007, 04:58 PM

Quote:

Originally Posted by Rc 415

Will this rearend work in my truck? its from a 1990 chevy
http://sfbay.craigslist.org/eby/pts/419084926.html

I don't know if it will work, but that's a pretty decent price if it's in good shape. Maybe go take a look at it and bring along a tape measure. Check the spring center spacing and the overall width and compare to what's on your truck now.

Pyrotechnic · 09-12-2007, 04:58 PM

I'm not sure on that newer rear end. I asked if I could put an old 12 bolt under a 88-98 truck and was told it would not work so I'm guessing the newer rear end under the older truck wont work either.I would go for a 73-87 rear end.

xtreme80 · 09-12-2007, 05:47 PM

I'm willing to bet also that there's something wrong with that rear. Even 10 bolts without ring and pinions still go for more than that around here...

**N2TRUX** · 09-12-2007, 08:55 PM

Anything can be made to work, but that rear end will not just bolt in and it has a much narrower track.

All of the guys above are correct about the 3.73 gears. I have had a quiet a few trucks with 3.73's and they perform much better than 3.42's...

Rc 415 · 09-12-2007, 08:58 PM

Quote:

Originally Posted by N2TRUX

Anything can be made to work, but that rear end will not just bolt in and it has a much narrower track.

Thats what I needed to know, thanks I'll keep on lookin and mabye even get somthin with posi.

D13 · 09-13-2007, 11:25 AM

And if / when you swap out the gears (not the whole rear end) mail me your 2.73's. I'll swap them out for my 3.08's behind the 6.2 in the '87 and get up to 24mpg. Since I'm not ever in a hurry (at least not with a 6.2) they'll do me right!

I have 3.43's in my 82 with 30's (14 bolt and posi) and the L6 would happily chirp them, right up until it burned up.

Rc 415 · 09-13-2007, 11:43 AM

If you want to pay shipping no problem, but how would you go about putting them in your self I heard its a very hard task to get them put in correctly.

MylilBowTie · 09-13-2007, 12:05 PM

If you use all the bearings and other parts. You can get lucky sometimes and not need to shim anything. But I would still say your money ahead getting a whole rear. Granted the whole rear is a good unit.

liljon285 · 09-13-2007, 12:07 PM

Everyone who has had gears has told me to get 3.42...its pretty much inbetween.

piecesparts · 09-13-2007, 04:29 PM

I had 3.42 gears with a 700 R4 and they worked fine with the 700R4 on my 84, but I changed over to 3.73 gears when I put in the larger cam and 383 stroker motor along with the 2400 stall torque converter. The 91 pickup that I drive daily has 3.42 gears and a 700 R4, connected to a throttle body fed 5.7 liter motor and it performs well at 20 MPG (the fuel injection throttle body is the trick here). I like the 3.73 gears and the acceleration that it gives me over the 3.42 gears. The RPMs on my different motors are around 2300 RPMs at 70 MPH on the 91 Silverado (29" tires) and the RPMs on the 84 GMC is at 2500 RPMs at 70 MPH. The 3.73 will eat up the 3.42 gears any day of the week, in an acceleration comparison.

My gas mileage in the 84 GMC went from 15.5 / 16 MPG to 14.5/15 MPG average with a 400 HP, 383 stroker motor and the 700R4 tranny. You will like either set, but if you want acceleration and pulling capability, consider the 3.73 gears and believe me the MPGs are not that much different. You can change that slightly by the tire size that you run.

09-10-2007, 10:19 PM	#1
Rc 415 Flat Black, & Chrome! Join Date: Jan 2007 Location: San Francisco Posts: 852	What rear end gears should I get? I've got a 30" tall tire in the back now, and I'm running 2.73 gears with an auto 700R4, I want to accelerate quick, but I'm not sure about what all gears are good for what in the rear, all I know is I am not happy with the rear gears in there now, I cant even chirp the tires, and the truck just doesn't accelerate quick at all, even on the freeway! __________________ 1983 Chevy C10 Stepside Sold http://s69.photobucket.com/albums/i76/rc_415/ Last edited by Rc 415; 09-10-2007 at 10:20 PM.

09-10-2007, 10:48 PM	#2
slugish Slugish Join Date: Jan 2005 Location: Earlysville, Va. Posts: 1,024	Re: What rear end gears should I get? with a 7004r with 30 in. tires , run at least a 3.73 rear end . should be perfect for what you want. you definitely will do some serious chirping with a 3.73, plus it will be very cruisable. best of both worlds.

09-11-2007, 01:26 AM	#3
xtreme80 Wishin' I had more money! Join Date: Feb 2007 Location: Eugene, OR Posts: 1,242	Re: What rear end gears should I get? Since you got an overdrive you could even go a little higher than 3.73 if you wanted, but that would probably be the best gear for your ride. Lucky you with overdrive, I'm doing a 3.73 on a 3 speed tranny... haha

09-11-2007, 08:40 AM	#4
Tink Registered User Join Date: May 2002 Location: VA Posts: 1,337	Re: What rear end gears should I get? Got 3.73s, 30s and a 700r4 on the 85. She will chirp a tire and pull like a frieght train on the highway. Turns about 2400rpm at 70mph. __________________ 69 Chevy C10 88 Sierra 02 2500 Suburban And too many S10s to list!

09-11-2007, 12:37 PM	#5
Rc 415 Flat Black, & Chrome! Join Date: Jan 2007 Location: San Francisco Posts: 852	Re: What rear end gears should I get? Will this rearend work in my truck? its from a 1990 chevy http://sfbay.craigslist.org/eby/pts/419084926.html __________________ 1983 Chevy C10 Stepside Sold http://s69.photobucket.com/albums/i76/rc_415/

09-12-2007, 03:08 PM	#6
Rc 415 Flat Black, & Chrome! Join Date: Jan 2007 Location: San Francisco Posts: 852	Re: What rear end gears should I get? up __________________ 1983 Chevy C10 Stepside Sold http://s69.photobucket.com/albums/i76/rc_415/

09-12-2007, 03:40 PM	#7
jchav62 1962 C-10 Join Date: Apr 2005 Location: Las Vegas, New Mexico Posts: 4,978	Re: What rear end gears should I get? I agree, 3.73's....Especially with an over drive tranny.. __________________ Joseph Chavez "See the USA in a Chevrolet!!" ......................_____ .........________//__{\_____ ,,,,,,,/__(O)___//___/__(O)_/ 1962 C10 Shortbed Fleetside 327/th350 GV overdrive 1974 C10 Longbed Fleetside 350/th350 "The Trash Truck" 1999 Chevy 2500 OBS, Longbed 5.7/4L80E 4x4 2015 GMC Sierra SLE 1500 4x4

09-12-2007, 04:58 PM	#9
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: What rear end gears should I get? I'm not sure on that newer rear end. I asked if I could put an old 12 bolt under a 88-98 truck and was told it would not work so I'm guessing the newer rear end under the older truck wont work either.I would go for a 73-87 rear end.

09-12-2007, 05:47 PM	#10
xtreme80 Wishin' I had more money! Join Date: Feb 2007 Location: Eugene, OR Posts: 1,242	Re: What rear end gears should I get? I'm willing to bet also that there's something wrong with that rear. Even 10 bolts without ring and pinions still go for more than that around here...

09-12-2007, 08:55 PM	#11
N2TRUX Happy to be here Join Date: Mar 2000 Location: Cypress, TX Posts: 39,023	Re: What rear end gears should I get? Anything can be made to work, but that rear end will not just bolt in and it has a much narrower track. All of the guys above are correct about the 3.73 gears. I have had a quiet a few trucks with 3.73's and they perform much better than 3.42's... __________________ Follow me on Facebook and Instagram @N2trux.com Articles- "Jake" the 84 to 74 crewcab "Elwood" the77_Remix 85 GMC Sierra "Scarlett" "Refining Sierra"

09-13-2007, 11:25 AM	#13
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: What rear end gears should I get? And if / when you swap out the gears (not the whole rear end) mail me your 2.73's. I'll swap them out for my 3.08's behind the 6.2 in the '87 and get up to 24mpg. Since I'm not ever in a hurry (at least not with a 6.2) they'll do me right! I have 3.43's in my 82 with 30's (14 bolt and posi) and the L6 would happily chirp them, right up until it burned up.

09-13-2007, 11:43 AM	#14
Rc 415 Flat Black, & Chrome! Join Date: Jan 2007 Location: San Francisco Posts: 852	Re: What rear end gears should I get? If you want to pay shipping no problem, but how would you go about putting them in your self I heard its a very hard task to get them put in correctly. __________________ 1983 Chevy C10 Stepside Sold http://s69.photobucket.com/albums/i76/rc_415/

09-13-2007, 12:05 PM	#15
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	Re: What rear end gears should I get? If you use all the bearings and other parts. You can get lucky sometimes and not need to shim anything. But I would still say your money ahead getting a whole rear. Granted the whole rear is a good unit. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

09-13-2007, 12:07 PM	#16
liljon285 That Guy Join Date: Sep 2005 Location: miami, fl Posts: 327	Re: What rear end gears should I get? Everyone who has had gears has told me to get 3.42...its pretty much inbetween. __________________ 1978 Chevy Scottdale Stepside, 3rd engine- 350c.i. built with cam and lifters, holley 670cfm carb. and intake,heads shaved .60. Truck is a project, and I am its restorererer!

09-13-2007, 04:29 PM	#17
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: What rear end gears should I get? I had 3.42 gears with a 700 R4 and they worked fine with the 700R4 on my 84, but I changed over to 3.73 gears when I put in the larger cam and 383 stroker motor along with the 2400 stall torque converter. The 91 pickup that I drive daily has 3.42 gears and a 700 R4, connected to a throttle body fed 5.7 liter motor and it performs well at 20 MPG (the fuel injection throttle body is the trick here). I like the 3.73 gears and the acceleration that it gives me over the 3.42 gears. The RPMs on my different motors are around 2300 RPMs at 70 MPH on the 91 Silverado (29" tires) and the RPMs on the 84 GMC is at 2500 RPMs at 70 MPH. The 3.73 will eat up the 3.42 gears any day of the week, in an acceleration comparison. My gas mileage in the 84 GMC went from 15.5 / 16 MPG to 14.5/15 MPG average with a 400 HP, 383 stroker motor and the 700R4 tranny. You will like either set, but if you want acceleration and pulling capability, consider the 3.73 gears and believe me the MPGs are not that much different. You can change that slightly by the tire size that you run.



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