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#1 |
Formerly- 1972SuperCheyenne
![]() Join Date: Oct 2008
Location: Wake Forest NC
Posts: 5,782
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6.2 manual to auto swap
I am changing the sm 465 in my crew cab to an automatic. It has 35 inch tires and 4.10 gears. Will i be okay with a turbo 400 or do I need an overdrive to be able to run happily at 70 miles an hour on the interstate? I don't want to over rev the 6.2 diesel to the point where I am hurting it or killing my gas mileage. Anyone who has experience with these please help me out. Does anyone know what is the optimal
cruising rpm for the 6.2 diesel? Thank you guys for all your help ahead of time. Posted via Mobile Device
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--Josh My Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=799218 A good crossthread is better than Loctite any day. Life is not about what you have, but who you have to share it with. |
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#2 |
Next!
Join Date: Jan 2003
Location: Eastern Pa.
Posts: 2,482
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Re: 6.2 manual to auto swap
This gets talked about on the steelsoldiers site all the time in the CUCV section. Take a look there and do some reading. I have both manual and auto with 6.2s, both stock tires, both 4:56s, they aren't speedsters but mine aren't meant for long rides of 70 mph.
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86 K30 CUCV M1028A1 86 K30 CUCV M1028a2 dually 86 K30 C&C 6.2 4:56s, 4M, 11,000 gvw, ex fire truck, now lowboy dump More square bodies and CUCVs than I care to admit to 2020 Silverado K3500HD Work truck |
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#3 |
Registered User
Join Date: May 2011
Location: rising sun in
Posts: 28
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Re: 6.2 manual to auto swap
my truck has the 3 speed automatic. i also have a well built 355. 33" tires. anything over 60-70 is just too much as a cruising speed. i am thinking about swapping for an overdrive myself. it is just nice to be able to get on the interstate if i choose to and roll out!
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#4 | |
Conversion Truck Addicted
Join Date: Sep 2009
Location: Denmark, Europe
Posts: 1,551
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Re: 6.2 manual to auto swap
Nv4500
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Thomas Quote:
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#5 |
Formerly- 1972SuperCheyenne
![]() Join Date: Oct 2008
Location: Wake Forest NC
Posts: 5,782
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Re: 6.2 manual to auto swap
Switching to an automatic because I tore a ligament/tendons in my ankle, thanks though.
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--Josh My Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=799218 A good crossthread is better than Loctite any day. Life is not about what you have, but who you have to share it with. Last edited by STOCKISH; 05-15-2011 at 09:22 PM. |
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#6 |
Registered User
Join Date: Sep 2000
Location: Gold Bar, WA
Posts: 1,216
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Re: 6.2 manual to auto swap
My diesel burb is set up with 4.10 gears, 35" tires, and a TH-400. I had an SM-465 in it and converted to the auto so my girfriend could drive it...she has arthritis pretty bad.
Anyways, before I rebuilt the TH-400, I didn't notice any change in mileage and 70mph is about as far as I would push it...but I drive like an old man too. Since I had the tranny rebuilt, my mileaqge went up a bit. I know 65mph is a nice speed for the diesel and I think 70 wouldn't be too bad either, but it's been a while since I've driven it at 70....all the highways near me top out at 60. I went with the TH-400 when I did the conversion because my Burb is also my tow rig.
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My Projects: 1960 GMC 1/2ton with 305 V6 (daily driver) 1963 Chevy 1/2ton 2wd...converting to 4x4 1967 Suburban 1/2ton 2wd My Girlfriends Projects 1985 Chevy Suburban 3/4ton 4x4 with 6.2L diesel, 4" lift, converted to TH-400, Warn Premium manual hubs, & Wildcat 315/75/R16 tires. (daily driver) 1978 Camaro Type LT with a Marine 350 & vortec heads, Rochester Carb, & roller cam 1978 Camaro Z28 |
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#7 |
Formerly- 1972SuperCheyenne
![]() Join Date: Oct 2008
Location: Wake Forest NC
Posts: 5,782
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Re: 6.2 manual to auto swap
Thanks buddy.
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--Josh My Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=799218 A good crossthread is better than Loctite any day. Life is not about what you have, but who you have to share it with. |
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#8 |
Gentleman Jim owner x2
![]() Join Date: Oct 2010
Location: West Des Moines, IA
Posts: 464
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Re: 6.2 manual to auto swap
Might as well point out the obvious here... you're going to be running the EXACT same RPM's with the TH400 as you are with the SM465. It's the same final drive of 1:1 on both transmissions. Are you happy with your current RPM's at 70 mph? If not, then go for the 700r4. I have a 3.40 rear end, and had a TH350 behind my 6.2 and HATED listening to the RPM's at anything over 70 mph. I went ahead and got a 700r4. And my fuel mileage was around 17 mpg's at 70, and 14 at 75 with the TH350. Haven't had it on the interstate yet with the 700r4.
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1975 GMC Gentleman Jim #1 -357 / 700r4 1975 GMC Gentleman Jim #2 -350 / TH350 |
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#9 | |
Formerly- 1972SuperCheyenne
![]() Join Date: Oct 2008
Location: Wake Forest NC
Posts: 5,782
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Re: 6.2 manual to auto swap
Quote:
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--Josh My Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=799218 A good crossthread is better than Loctite any day. Life is not about what you have, but who you have to share it with. |
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#10 | |
Gentleman Jim owner x2
![]() Join Date: Oct 2010
Location: West Des Moines, IA
Posts: 464
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Re: 6.2 manual to auto swap
Quote:
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1975 GMC Gentleman Jim #1 -357 / 700r4 1975 GMC Gentleman Jim #2 -350 / TH350 |
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#11 |
Formerly- 1972SuperCheyenne
![]() Join Date: Oct 2008
Location: Wake Forest NC
Posts: 5,782
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Re: 6.2 manual to auto swap
Thanks, do you know what RPMs you were turning? I know I can use a RPM calculator but I dont know your gear ratio or tire height.
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--Josh My Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=799218 A good crossthread is better than Loctite any day. Life is not about what you have, but who you have to share it with. |
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#12 |
Slots go on anything!
Join Date: May 2003
Location: Richardson, TX
Posts: 5,957
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Re: 6.2 manual to auto swap
I would go for the 700R4 because it has a lower 1st and 2nd gear than a TH400 also. That's a heavy truck to get moving.
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1974 Jimmy- 5.3/4L80e/NP241 |
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#13 |
Resident of Here
Join Date: May 2008
Location: Wesley Chapel, FL, USA
Posts: 7,716
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Re: 6.2 manual to auto swap
With a TH400, 4.10's and 35's you would be turning 2952 of the 3600 total rpm's the 6.2 has. That's at 75mph. Same with the current SM465.
I would recommend a 700R4 or even better a 4L80E. The 700R4 has a 8600GVWR. The 4L80E has a 16000GVWR. Pick the latter. At 75mph the 700R4 would be turning 2066rpm. The 4L80E would be turning 2214 rpm. Big difference over the TH400 and SM465. My suburban at 75mph turns 2122rpm. She isn't screaming. I've hit 110mph and she still doesn't scream. They'll run wide-open for years. But never the less, I would get the 4L80E if I were you. This guy has good stuff. http://www.transmissioncenter.net/4l80e.htm
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~Bradley~ 2004 Black GTO LS2/T56 too much to list ![]() Miss having a truck ![]() |
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#14 |
Resident of Here
Join Date: May 2008
Location: Wesley Chapel, FL, USA
Posts: 7,716
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Re: 6.2 manual to auto swap
You can get an adapter for the 4L80E to t-case. $500-700. Yikes.
Here's a trans and some other parts. http://raleigh.craigslist.org/pts/2337914791.html http://raleigh.craigslist.org/pts/2346699464.html http://www.summitracing.com/parts/ADD-50-0410
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~Bradley~ 2004 Black GTO LS2/T56 too much to list ![]() Miss having a truck ![]() Last edited by thirdstreettito; 05-16-2011 at 08:27 AM. |
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#15 |
Formerly- 1972SuperCheyenne
![]() Join Date: Oct 2008
Location: Wake Forest NC
Posts: 5,782
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Re: 6.2 manual to auto swap
I'm like you on the adapters, Yikes! I am pondering a 2wd 4l80e(cheaper) and a divorced transfer case. I am just trying not to have to swallow $2000 for a auto trans swap!
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--Josh My Build Thread:http://67-72chevytrucks.com/vboard/s...d.php?t=799218 A good crossthread is better than Loctite any day. Life is not about what you have, but who you have to share it with. |
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#16 |
Resident of Here
Join Date: May 2008
Location: Wesley Chapel, FL, USA
Posts: 7,716
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Re: 6.2 manual to auto swap
It'll save you that in fuel over the next few years the way the prices are going.
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~Bradley~ 2004 Black GTO LS2/T56 too much to list ![]() Miss having a truck ![]() |
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