Help with rear end. Gears? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DJMAN · 11-09-2009, 06:28 PM

I have a 71'LWB which had a 250 w/3 on the tree. I have just replaced it with 350 TBI and 350 auto trans.

My questions is what rear end (gears) was installed on this truck? What gears should I install? This is not going to be a daily driver, just on weekends or car shows.

I will post pics when it returns from the paint shop.

Thanks,

DJMAN

LOW DOUGH · 11-09-2009, 06:30 PM

I think a 3 on the tree came with 4:11's. Someone will correct me if I'm wrong.

edit: and if you run 4:11's and a TH350 you will be screaming (high RPM's) down the highway. I wish I went with a 700R4 for the overdrive.

Wrenchbender Ret · 11-09-2009, 06:35 PM

It probably came with 3.90. I would change to 3.08. They are plentiful for these trucks.

DJMAN · 11-09-2009, 06:43 PM

Quote:

Originally Posted by LOW DOUGH

I think a 3 on the tree came with 4:11's. Someone will correct me if I'm wrong.

edit: and if you run 4:11's and a TH350 you will be screaming (high RPM's) down the highway. I wish I went with a 700R4 for the overdrive.

Yes as I went down the freeway is was screaming. But I think my exhaust drowned it out.

So my gears need replacing.

Dark Knight · 11-09-2009, 08:41 PM

250 I6/ 3-speed came with 3.73 gears. I'd change it over to a 3.08 if you do a lot of highway driving. I've got a little 6 banger and a 3-speed in my truck with 3.08 gears. I just couldn't take that 10 MPG from the 4.56 gears I had. It'll still light up the pavement! Let's just say the road isn't asphalt colored anymore in front of my house...

redbaron69 · 11-09-2009, 09:28 PM

if i had to guess i would say 3.73 my 90 z71 has a th350 in it and 3.73 gears. tons of take off and pulling power, but it whinds up tight on the interstate. i think i may put a 3.42 in my 69 when i get to that point. i think a 3.42 would be a happy medium. just my .02 cents worth

Shyguy · 11-09-2009, 10:50 PM

My son is running 3.42 gears in his '67 swb with a 454 and 3 on the floor.

These gears seem to be working out great for the way he drives his truck.

Danny

Jim_PA · 11-09-2009, 11:01 PM

For fair-weather, fun driving.. 3.73 or 4:11 will be perfect.

hchad18 · 11-09-2009, 11:05 PM

My 250 I-6 3 speed had 3:73's.

Longhorn Man · 11-10-2009, 01:25 AM

1/2 ton would be 3.73
3/4 ton would be 4.57

DJMAN · 11-10-2009, 02:29 AM

Thanks for all the info guys, it was very helpful.

I'm going to run taller tires in the rear for now 275/70/15 (275/60/15 in the front) till I change the gears.

Thanks

DJMAN

LOW DOUGH · 11-10-2009, 10:42 AM

I really thought i read somewere the 3 speeds came with 4:11 and autos came with I think it was 3:73.

But I have been known to be wrong.......

a lot LOL

69GMCLonghorn · 11-10-2009, 12:02 PM

More gears are always better, but in lieu of that, go with the 3.08's. It'll get better mileage, but just the overall driveability will improve tenfold.

big_al_71 · 11-10-2009, 12:36 PM

my truck was a 307 with a 3spd on the column and when I took it apart it had 373 gears in there. I now have a built 406 with a th350 and still running the 373's and they are alot of fun everywhere I drive...Here is a pict of what it looked like when we took it apart..

69GMCLonghorn · 11-10-2009, 01:02 PM

Question for someone who might know more than I: My cousin had a 1980 K5 Jimmy. It had a 350/350 and had the HIGHEST highway gears I've ever seen! I think 1st gear wrapped out around 50 - 55 MPH. 2nd was an easy 80 MPH. What gears did this thing have in it?

Jim_PA · 11-10-2009, 01:29 PM

Quote:

Originally Posted by 69GMCLonghorn

More gears are always better, but in lieu of that, go with the 3.08's. It'll get better mileage, but just the overall driveability will improve tenfold.

It's a weekend toy, stick with the fun gears.

profe56 · 11-11-2009, 10:01 PM

3.73 and 700R4 could be a good match

lsx72 · 11-11-2009, 11:54 PM

imo 3.42 gears are the best on the planet.. but thats just me...

Longhorn Man · 11-12-2009, 10:06 AM

Quote:

Originally Posted by LOW DOUGH

I really thought i read somewere the 3 speeds came with 4:11 and autos came with I think it was 3:73...

There's some exceptions, and it differs with engine size a little but, but the general rule on this was 3.73 was standard with 3 speed, 3.07 with 4 speed and automatic... in 1/2 ton.
3/4 tons got a 4.56 in manuals, and a 4.10 in automatics, unless big block, which got a 3.54 with auto (not sure on manuals)
Again, some variables in there, but genericly, that's acurate.

TheOldGM · 11-12-2009, 10:13 AM

I thought 3.08 gears were standard in 1971. Anything other than that would be listed as a SEO option listed on the RPO sheet located on the backside of the glove box door.

Longhorn Man · 11-12-2009, 11:07 AM

nope.
technicly, 3.08 gears came in cars back then, not trucks.
the base equipped truck (talkin 1/2 ton) was 3.73 in bit the CE and CS series trucks.
So base truck gearing was 3.73.
With some options, you got 'standard options' or 'required options'. that's when the gearing comes comes into play, and is generally listed as I posted above.

68Stepbed · 11-12-2009, 02:50 PM

3-speed trucks...3.73:1 gears
4=speed trucks...4.11:1 gears
Auto trucks........3.07:1 gears

This was the basic standards for all 1/2 ton trucks. Any special orders could've been changed.

To answer your main question though, 3.42 would be the best all around gear with a TH350 or 700R4 tranny. The 3.73's will be better for something you don't plan to get on the highway too much.

1-PU70 · 11-12-2009, 04:57 PM

I may have missed it but what size tires are you running? I have 3:73's with a 700R4 and a 31" tire. At 70 miles an hour im at about 1800RPM's. With the BB its not a problem but with a 6 banger it might. I think I might be going to 4:10's after I check my cam specs.

67chevemall · 11-12-2009, 05:16 PM

70 miles at 1800 is darn good...are ya sure with 3:73's

1-PU70 · 11-12-2009, 05:20 PM

Im using a autometer sport comp programmabale spedo. So its prity close. But I havent checked with my GPS.

11-09-2009, 06:28 PM	#1
DJMAN Registered User Join Date: Jan 2008 Location: Fresno Ca Posts: 82	Help with rear end. Gears? I have a 71'LWB which had a 250 w/3 on the tree. I have just replaced it with 350 TBI and 350 auto trans. My questions is what rear end (gears) was installed on this truck? What gears should I install? This is not going to be a daily driver, just on weekends or car shows. I will post pics when it returns from the paint shop. Thanks, DJMAN

11-09-2009, 06:30 PM	#2
LOW DOUGH I'M TRUCK CRAZY! Join Date: Oct 2006 Location: Sachse, TEXAS Posts: 1,737	Re: Help with rear end. Gears? I think a 3 on the tree came with 4:11's. Someone will correct me if I'm wrong. edit: and if you run 4:11's and a TH350 you will be screaming (high RPM's) down the highway. I wish I went with a 700R4 for the overdrive. Last edited by LOW DOUGH; 11-09-2009 at 06:31 PM.

11-09-2009, 06:35 PM	#3
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,228	Re: Help with rear end. Gears? It probably came with 3.90. I would change to 3.08. They are plentiful for these trucks.

11-09-2009, 08:41 PM	#5
Dark Knight Registered User Join Date: Dec 2008 Location: Pleak, Texas Posts: 420	Re: Help with rear end. Gears? 250 I6/ 3-speed came with 3.73 gears. I'd change it over to a 3.08 if you do a lot of highway driving. I've got a little 6 banger and a 3-speed in my truck with 3.08 gears. I just couldn't take that 10 MPG from the 4.56 gears I had. It'll still light up the pavement! Let's just say the road isn't asphalt colored anymore in front of my house... __________________ -1967 Chevrolet Fleetside LWB- 350 V8 w/thumpr cam, NV3500, 3.08 gears, A/C, PS -1983 Chevy Silverado C1500- 383 stroker, TH400 -1989 Chevy Silverado K1500 SWB- 5.3L swap, 700R4, 3.42 gears -And a '66 Ford Mustang- 200 I6, C4 trans, rust bucket "The only thing we have to fear is fear itself." -FDR (and maybe rust too) You've gotta be able to stop and steer before you can go fast!

11-09-2009, 09:28 PM	#6
redbaron69 Registered User Join Date: Jan 2009 Location: marion nc Posts: 588	Re: Help with rear end. Gears? if i had to guess i would say 3.73 my 90 z71 has a th350 in it and 3.73 gears. tons of take off and pulling power, but it whinds up tight on the interstate. i think i may put a 3.42 in my 69 when i get to that point. i think a 3.42 would be a happy medium. just my .02 cents worth __________________ 69 short fleet 350/350 "under construction" 70 short step 307/3 speed

11-09-2009, 10:50 PM	#7
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: Help with rear end. Gears? My son is running 3.42 gears in his '67 swb with a 454 and 3 on the floor. These gears seem to be working out great for the way he drives his truck. Danny __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.

11-09-2009, 11:01 PM	#8
Jim_PA Registered User Join Date: May 2005 Location: PA Posts: 2,696	Re: Help with rear end. Gears? For fair-weather, fun driving.. 3.73 or 4:11 will be perfect.

11-09-2009, 11:05 PM	#9
hchad18 Registered User Join Date: Mar 2006 Location: AZ Posts: 372	Re: Help with rear end. Gears? My 250 I-6 3 speed had 3:73's.

11-10-2009, 01:25 AM	#10
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Help with rear end. Gears? 1/2 ton would be 3.73 3/4 ton would be 4.57

11-10-2009, 02:29 AM	#11
DJMAN Registered User Join Date: Jan 2008 Location: Fresno Ca Posts: 82	Re: Help with rear end. Gears? Thanks for all the info guys, it was very helpful. I'm going to run taller tires in the rear for now 275/70/15 (275/60/15 in the front) till I change the gears. Thanks DJMAN

11-10-2009, 10:42 AM	#12
LOW DOUGH I'M TRUCK CRAZY! Join Date: Oct 2006 Location: Sachse, TEXAS Posts: 1,737	Re: Help with rear end. Gears? I really thought i read somewere the 3 speeds came with 4:11 and autos came with I think it was 3:73. But I have been known to be wrong....... a lot LOL Last edited by LOW DOUGH; 11-10-2009 at 10:43 AM.

11-10-2009, 12:02 PM	#13
69GMCLonghorn Registered User Join Date: Dec 2006 Location: Porter Ranch, CA Posts: 978	Re: Help with rear end. Gears? More gears are always better, but in lieu of that, go with the 3.08's. It'll get better mileage, but just the overall driveability will improve tenfold.

11-10-2009, 12:36 PM	#14
big_al_71 Registered User Join Date: Jun 2008 Location: South Florida Posts: 11,375	Re: Help with rear end. Gears? my truck was a 307 with a 3spd on the column and when I took it apart it had 373 gears in there. I now have a built 406 with a th350 and still running the 373's and they are alot of fun everywhere I drive...Here is a pict of what it looked like when we took it apart.. Attached Images __________________ Get your facts first, and then you can distort them as much as you please!!!!!. Sylvester's build thread >>>http://67-72chevytrucks.com/vboard/s...ht=big+rebuild

11-10-2009, 01:02 PM	#15
69GMCLonghorn Registered User Join Date: Dec 2006 Location: Porter Ranch, CA Posts: 978	Re: Help with rear end. Gears? Question for someone who might know more than I: My cousin had a 1980 K5 Jimmy. It had a 350/350 and had the HIGHEST highway gears I've ever seen! I think 1st gear wrapped out around 50 - 55 MPH. 2nd was an easy 80 MPH. What gears did this thing have in it?

11-11-2009, 10:01 PM	#17
profe56 Registered User Join Date: Nov 2008 Location: Chula Vista California Posts: 526	Re: Help with rear end. Gears? 3.73 and 700R4 could be a good match



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11-11-2009, 11:54 PM	#18
lsx72 Registered User Join Date: Nov 2009 Location: greenville,sc Posts: 89	Re: Help with rear end. Gears? imo 3.42 gears are the best on the planet.. but thats just me...

11-12-2009, 10:13 AM	#20
TheOldGM Registered User Join Date: Oct 2009 Location: Janesville, WI Posts: 18	Re: Help with rear end. Gears? I thought 3.08 gears were standard in 1971. Anything other than that would be listed as a SEO option listed on the RPO sheet located on the backside of the glove box door. __________________ Gas flows from more places then my rear....

11-12-2009, 11:07 AM	#21
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Help with rear end. Gears? nope. technicly, 3.08 gears came in cars back then, not trucks. the base equipped truck (talkin 1/2 ton) was 3.73 in bit the CE and CS series trucks. So base truck gearing was 3.73. With some options, you got 'standard options' or 'required options'. that's when the gearing comes comes into play, and is generally listed as I posted above.

11-12-2009, 02:50 PM	#22
68Stepbed Registered User Join Date: Mar 2005 Location: 10-Uh-See Posts: 5,609	Re: Help with rear end. Gears? 3-speed trucks...3.73:1 gears 4=speed trucks...4.11:1 gears Auto trucks........3.07:1 gears This was the basic standards for all 1/2 ton trucks. Any special orders could've been changed. To answer your main question though, 3.42 would be the best all around gear with a TH350 or 700R4 tranny. The 3.73's will be better for something you don't plan to get on the highway too much. __________________ Matt 68 C10 stepside, LS1/700R4, TCI Engineering suspension system Last edited by 68Stepbed; 11-12-2009 at 02:53 PM.

11-12-2009, 04:57 PM	#23
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	Re: Help with rear end. Gears? I may have missed it but what size tires are you running? I have 3:73's with a 700R4 and a 31" tire. At 70 miles an hour im at about 1800RPM's. With the BB its not a problem but with a 6 banger it might. I think I might be going to 4:10's after I check my cam specs. __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

11-12-2009, 05:16 PM	#24
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	Re: Help with rear end. Gears? 70 miles at 1800 is darn good...are ya sure with 3:73's __________________ 1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD

11-12-2009, 05:20 PM	#25
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	Re: Help with rear end. Gears? Im using a autometer sport comp programmabale spedo. So its prity close. But I havent checked with my GPS. __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

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