Inline 6 drive train advice - The 1947 - Present Chevrolet & GMC Truck Message Board Network

62 bigwindow · 03-26-2014, 09:38 PM

I have come to the point on my 66 that I am ready to install motor and trans
to mock up ride height for the bag mounts on the rearend and have decided in order to be a little different go with a mild 250 inline 6. My question to you guys is what trans to go with and what rear end gearing? I plan to run the stock 12 bolt rear end. I was thinking of the 700r for the overdrive and ability to cruise at highway speeds. As always thanks in advance for any and all input..

boucher racing · 03-26-2014, 09:54 PM

I can speak from experience. I have run a stock inline 250 with 3 on tree. stock Inline 250 with T5. Built turbo'd inline 250 with T5. Built turbo'd inline 250 with 700r4. My rear end is a 3.54 gear.

The most pep was with the T5. Very little drivetrain loss. Great gear ratio spreads.

The 700r4 is the most comfortable, but does feel a bit slower about 75% of the time. The other 25% the turbo is spooled up and its a raped ape!

If the inline 250 is not making big power, I would stick with a T5. Plus, the swap is much easier and far less money. I switched just because a auto pairs well with a turbo.

Boucher'

Lugnutz65 · 03-26-2014, 10:12 PM

It's important to match the OD gear with the rear diff. Too much OD with the wrong diff and it will not drive well in OD.

3.73 rear works well with a 0.72 OD
3.42 rear works well with a 0.86 OD
3.08 rear is hard to match with OD because it will probably cause an inline 6 to lug in OD.

I'm enthusiastic about T5s but finding one with a cable speedo S10 tailhousing is tough. If you have bucket seats then just use a Camaro tail housing with a cable speedo output - those are easy to find.

62 bigwindow · 03-26-2014, 10:46 PM

Sorry I did forget to mention I do want to use automatic transmission

NEWFISHER · 03-27-2014, 12:21 AM

My 50 burb sports a warmed over 250, 700r4 and 3:73. Gets 19 mpg with a 29" tall tire and is a great daily combo, cruising and pulls a 4000lb camp trailer a lot. I with I had 4:10s when pulling the hills with the trailer but only 20 days out of the summer I can live with the better daily feel with the 3:73s. I'm running a heated clifford intake and a Holley 390 which is super easy to run the TV cable set up for the 700r4.

03-26-2014, 09:38 PM	#1
62 bigwindow Registered User Join Date: Apr 2011 Location: Mocksville NC Posts: 824	Inline 6 drive train advice I have come to the point on my 66 that I am ready to install motor and trans to mock up ride height for the bag mounts on the rearend and have decided in order to be a little different go with a mild 250 inline 6. My question to you guys is what trans to go with and what rear end gearing? I plan to run the stock 12 bolt rear end. I was thinking of the 700r for the overdrive and ability to cruise at highway speeds. As always thanks in advance for any and all input..

03-26-2014, 09:54 PM	#2
boucher racing Registered User Join Date: Feb 2009 Location: Nashville TN Posts: 294	Re: Inline 6 drive train advice I can speak from experience. I have run a stock inline 250 with 3 on tree. stock Inline 250 with T5. Built turbo'd inline 250 with T5. Built turbo'd inline 250 with 700r4. My rear end is a 3.54 gear. The most pep was with the T5. Very little drivetrain loss. Great gear ratio spreads. The 700r4 is the most comfortable, but does feel a bit slower about 75% of the time. The other 25% the turbo is spooled up and its a raped ape! If the inline 250 is not making big power, I would stick with a T5. Plus, the swap is much easier and far less money. I switched just because a auto pairs well with a turbo. Boucher' __________________ Build Threads: "JED" 66 GMC C1000 http://inliners.org/ubbthreads/ubbth...1857#Post61857 "Cropwell" 66 C10 http://67-72chevytrucks.com/vboard/s...d.php?t=587639

03-26-2014, 10:12 PM	#3
Lugnutz65 Registered User Join Date: Jan 2013 Location: Columbia, SC Posts: 1,927	Re: Inline 6 drive train advice It's important to match the OD gear with the rear diff. Too much OD with the wrong diff and it will not drive well in OD. 3.73 rear works well with a 0.72 OD 3.42 rear works well with a 0.86 OD 3.08 rear is hard to match with OD because it will probably cause an inline 6 to lug in OD. I'm enthusiastic about T5s but finding one with a cable speedo S10 tailhousing is tough. If you have bucket seats then just use a Camaro tail housing with a cable speedo output - those are easy to find. __________________ My 65 C10 build: www.lugnutz65chevystepside.weebly.com Want to know more about T5 transmissions? My website has a T5 Info Page and a Step by Step T5 rebuild.

03-26-2014, 10:46 PM	#4
62 bigwindow Registered User Join Date: Apr 2011 Location: Mocksville NC Posts: 824	Re: Inline 6 drive train advice Sorry I did forget to mention I do want to use automatic transmission

03-27-2014, 12:21 AM	#5
NEWFISHER Registered User Join Date: Sep 2012 Location: Oregon Posts: 3,303	Re: Inline 6 drive train advice My 50 burb sports a warmed over 250, 700r4 and 3:73. Gets 19 mpg with a 29" tall tire and is a great daily combo, cruising and pulls a 4000lb camp trailer a lot. I with I had 4:10s when pulling the hills with the trailer but only 20 days out of the summer I can live with the better daily feel with the 3:73s. I'm running a heated clifford intake and a Holley 390 which is super easy to run the TV cable set up for the 700r4. __________________ GOD BLESS AMERICA!



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