Needs some ideas to make my 70 more street friendly - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Mog · 04-20-2011, 11:47 PM

Need suggestions to lower my RPMs when I'm at highway speeds. I have a TH350 that is in its highest gear at around 25mph. Love another gear but don't have the funds for a new tranny right now. Changing gear ratios? That's not much cheaper right? What about changing shift points?

bouncytruck · 04-20-2011, 11:57 PM

What gears are you running and what size tires?

Mog · 04-21-2011, 12:10 AM

4.11 gears with LT245/75R16 tires. Getting 33's in the near future though.

IGOR · 04-21-2011, 05:13 PM

Overdrive tranny will give you best bang for your buck. Lots of people (or at least two I know of: AJ, VT) have had good luck with the 700R4 / NP208 combo. I would start looking around for a used setup or try and rob one out of a cheap parts K5 of newer vintage.

Mike C · 04-23-2011, 07:53 PM

Wow. Highway ain't much fun, huh? 4.11 and an auto would like 35" or 37" tires. Will make the biggest difference, especially if you are going to have to get tires anyhow. But 33's is about all that will fit without 4" lift.

No cheap way out of this one. 35's and a lift will cost $1500 plus wheels if you need them. TH700R4 conversion will cost at least $2000 to use your 205 case, and gears and swap will run you $1000. At least.

Get the tires first, you will be surprised at the difference it makes. I went to 28" tall tires on my Camaro from 26" and it was quite noticeable.

You might find someone to swap you front and rear axles, but that most likely will get you 3.73. Which is only a 10% reduction, but combined with a set of 33's would at least make it realistically driveable.

71Rat · 04-23-2011, 08:17 PM

find a set of axles is probly your cheapest bet to swap. can normally find 1/2 tons for cheap or free when people swap to 3/4 or 1 tons

Mog · 04-23-2011, 09:36 PM

Guess I'll see where I'm at (with funds too) once I get the 33's. Not sure I want to go much bigger, won't be able to fit in the garage! Want to give it a wider stance, which I think will require wider rims. I figure I could sell the TH350 to help offset the cost of a 700R4. The 350 is less than a year old, Jasper. Gotta be a market for those, right? Thanks for all the suggestions.

1972CST · 04-23-2011, 10:19 PM

You could twist my arm and I might trade your 4.10 axles for my 3.07 axles...

that would get your RPM,s down

*72lb4x4* · 04-23-2011, 11:32 PM

With a K5, a trans and TC are probably easier than diffs or diff gears front and rear.

04-20-2011, 11:47 PM	#1
Mog Registered User Join Date: Dec 2010 Location: Houston, TX Posts: 38	Needs some ideas to make my 70 more street friendly Need suggestions to lower my RPMs when I'm at highway speeds. I have a TH350 that is in its highest gear at around 25mph. Love another gear but don't have the funds for a new tranny right now. Changing gear ratios? That's not much cheaper right? What about changing shift points? __________________ 70 Blazer K5

04-20-2011, 11:57 PM	#2
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,049	Re: Needs some ideas to make my 70 more street friendly What gears are you running and what size tires? __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

04-21-2011, 12:10 AM	#3
Mog Registered User Join Date: Dec 2010 Location: Houston, TX Posts: 38	Re: Needs some ideas to make my 70 more street friendly 4.11 gears with LT245/75R16 tires. Getting 33's in the near future though. __________________ 70 Blazer K5

04-21-2011, 05:13 PM	#4
IGOR Registered User Join Date: Feb 2003 Location: Damascus, OR Posts: 260	Re: Needs some ideas to make my 70 more street friendly Overdrive tranny will give you best bang for your buck. Lots of people (or at least two I know of: AJ, VT) have had good luck with the 700R4 / NP208 combo. I would start looking around for a used setup or try and rob one out of a cheap parts K5 of newer vintage. __________________ -Ben 1972 CST K5 - Undergoing frame off, 8.1/4L80E/NP205, 3/4 ton, 8" lift, currently a pile of parts that when assembled resemble a Blazer 1972 K10 - Rust Bucket, TBD 1976 C10 SWB, 350 / T350 My blazer build thread: https://ck5.com/forums/builds/72-k5-...17-update.410/

04-23-2011, 07:53 PM	#5
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,713	Re: Needs some ideas to make my 70 more street friendly Wow. Highway ain't much fun, huh? 4.11 and an auto would like 35" or 37" tires. Will make the biggest difference, especially if you are going to have to get tires anyhow. But 33's is about all that will fit without 4" lift. No cheap way out of this one. 35's and a lift will cost $1500 plus wheels if you need them. TH700R4 conversion will cost at least $2000 to use your 205 case, and gears and swap will run you $1000. At least. Get the tires first, you will be surprised at the difference it makes. I went to 28" tall tires on my Camaro from 26" and it was quite noticeable. You might find someone to swap you front and rear axles, but that most likely will get you 3.73. Which is only a 10% reduction, but combined with a set of 33's would at least make it realistically driveable. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

04-23-2011, 08:17 PM	#6
71Rat ran out of money Join Date: Apr 2003 Location: northern, NJ Posts: 925	Re: Needs some ideas to make my 70 more street friendly find a set of axles is probly your cheapest bet to swap. can normally find 1/2 tons for cheap or free when people swap to 3/4 or 1 tons __________________ Modify everything, leave nothing alone!~

04-23-2011, 09:36 PM	#7
Mog Registered User Join Date: Dec 2010 Location: Houston, TX Posts: 38	Re: Needs some ideas to make my 70 more street friendly Guess I'll see where I'm at (with funds too) once I get the 33's. Not sure I want to go much bigger, won't be able to fit in the garage! Want to give it a wider stance, which I think will require wider rims. I figure I could sell the TH350 to help offset the cost of a 700R4. The 350 is less than a year old, Jasper. Gotta be a market for those, right? Thanks for all the suggestions. __________________ 70 Blazer K5

04-23-2011, 10:19 PM	#8
1972CST Registered User Join Date: Mar 2008 Location: Concord NC Posts: 511	Re: Needs some ideas to make my 70 more street friendly You could twist my arm and I might trade your 4.10 axles for my 3.07 axles... that would get your RPM,s down

04-23-2011, 11:32 PM	#9
72lb4x4 Account Suspended Join Date: Jul 2006 Location: DFW Posts: 1,427	Re: Needs some ideas to make my 70 more street friendly With a K5, a trans and TC are probably easier than diffs or diff gears front and rear.



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