![]() |
Register or Log In To remove these advertisements. |
|
|
![]() |
|
Thread Tools | Display Modes |
![]() |
#1 |
Registered User
Join Date: Mar 2011
Location: Hesperia, California
Posts: 3
|
What Gears for a TH350 Trans
I am a Newbie here, and I have a small dilemma.... I own a 1969 Chev. C-20 equipped with a 350ci engine, I believe a TH350 trans (although the vacuum modulator is located on the right front of trans) and 4.10 rear end gears. It came with 16.5 tires and split rims, but I have changed them to 245/75/16 (30" tall) My problem is trying to figure out which gears would be better suited for Highway use. With the 4.10 gears I turn about 3500 RPM at 65-70 MPH and get real crappy fuel mileage. Any suggestions ?
|
![]() |
![]() |
![]() |
#2 |
Registered User
Join Date: Oct 2005
Location: Iowa
Posts: 136
|
Re: What Gears for a TH350 Trans
3.07 is what is in most half tons. That works pretty well for highway and most uses. A 3.42 would probably be the most I would drop to, depending on what you want to use it for.
|
![]() |
![]() |
![]() |
#3 |
Registered User
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,507
|
Re: What Gears for a TH350 Trans
I run pretty much the same setup in my 3/4 ton. Same engine, trans gear ratio an tire size.
As my truck likes to cruise right about 58 mph with the 4.11 I am going to put in the 3.55 Posi that I bought a while back to get the engine rpm down to the same as it now as at 57/58 but running at 70 on the freeway. Here is a pretty easy to use speed x rpm calculator that I use quite a bit. http://www.csgnetwork.com/multirpmcalc.html Here is one that is fun to play with but the options are limited. http://vexer.com/automotive-tools/speed-rpm-calculator A bit of a different one from Wallace Racing http://www.wallaceracing.com/gear-speed.php You have to scroll down to see the speeds. They also have calculators for a lot of car/truck stuff by clicking the back to calculators link. |
![]() |
![]() |
![]() |
#4 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
|
Re: What Gears for a TH350 Trans
if you have the eaton rear, the 4.10 is as good as you'll get. Time to decide what kind of rear you want
|
![]() |
![]() |
![]() |
Bookmarks |
|
|