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03-29-2010, 11:04 PM | #1 |
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Adding overdrive to a TH350?
I know I've seen bolt on overdrive units, but can't seem to find any on the net. Anyone have any ideas on how to add overdrive to a TH350 and not break the bank?
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03-29-2010, 11:07 PM | #2 |
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Re: Adding overdrive to a TH350?
The most popular is Gear Vendors. They aren't cheap. Around $2400. It would be cheapier to get a 700R4. Just a thought!
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03-29-2010, 11:10 PM | #3 |
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Re: Adding overdrive to a TH350?
Gear Vendors and US Gear are the two I know of.
A complete install of a GV (do it yourself) is about $3000 when all said and done, maybe more. The US gear unit is a little cheaper. Not sure what your budget is, but to me it's a waste of money. If you have a stock to mild engine, you're much better off getting a 700R4.
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1977 GMC Sierra Grande Last edited by Pyrotechnic; 03-29-2010 at 11:10 PM. |
03-29-2010, 11:21 PM | #4 |
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Re: Adding overdrive to a TH350?
Gear vendors, that's the one I remember seeing. $3000, ouch. I think an 700R4 would be much better, anyone know the average cost of setting one up in an old truck like ours?
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03-30-2010, 12:14 AM | #5 |
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Re: Adding overdrive to a TH350?
....or try getting a 200-4r (built up of course). The 200-4r is the same length as a turbo350, has a different ratio for 1st gear(and 2nd?) for a better 1-2 shift w/o the bog, and has a slightly lower (.67) overdrive. I think (not sure) that even the spline count is the same...meaning you can use your old driveshaft. I think the only real change other then the TV cable, is the tail mounting location, meaning slight changes to your tranny crossmember. I'm no expert so I could be off on some of these details.
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Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken |
03-30-2010, 12:51 AM | #6 |
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Re: Adding overdrive to a TH350?
thanks for the info.
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03-30-2010, 08:31 AM | #7 | |
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Re: Adding overdrive to a TH350?
Quote:
TH350_________TH400 Lo 2.52 2.75____2.48 2.75 2 1.52 1.52____1.48 1.57 3 1.00 1.00____1.00 1.00 200-4R__700R4/4L60E__4L80E/4L85E Lo 2.78______3.06_________2.48 2 1.57______1.63_________1.48 3 1.00______1.00_________1.00 4 0.67______0.70_________0.75 http://www.tciauto.com/Products/Tech...ear_ratios.asp
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03-30-2010, 07:40 PM | #8 |
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Re: Adding overdrive to a TH350?
I have a TH350 in my '85 and having a motor machined as we speak,but was wanting overdrive also. Are there any computer hook ups for the 700r4? Can you just bolt it up to a mild motor and ride?
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03-30-2010, 09:26 PM | #9 |
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Re: Adding overdrive to a TH350?
700-r4 and 200-4r only require a a TV (throttle value?) cable...but it has to be setup right or you can burn up the new tranny.
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Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken |
03-30-2010, 11:22 PM | #10 |
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Re: Adding overdrive to a TH350?
what about just going with a 400 with a lock up converter?
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03-30-2010, 11:45 PM | #11 |
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Re: Adding overdrive to a TH350?
I've got a TH350C with a lockup converter, and I guess my highway RPM's aren't too bad compared to others, I just do alot of highway travel to and from school everyday and would like something lower than 2500 RPM's @ 70mph
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03-31-2010, 08:08 AM | #12 |
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Re: Adding overdrive to a TH350?
You also need to control the lock up converter some how.
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74 GMC SWB Project "Sin-thia" Static Dropped 8"f/10"r http://67-72chevytrucks.com/vboard/s...d.php?t=460030 97 GMC reg cab short bed, 4.3V6 / 5spd, daily driver 220,000 miles, all stock for now |
03-31-2010, 10:51 AM | #13 |
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Re: Adding overdrive to a TH350?
forgot about that. Is there a diagram somewhere for the 4 wire connector and how to rig up a switch for it? I'd like to be able to keep the lockout "locked out" unless I'm cruising 80 or something and need it.
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Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken |
03-31-2010, 03:32 PM | #14 |
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Re: Adding overdrive to a TH350?
Not sure about that, but I do know that B&M has a kit that will control your converter and it is adjustable from 30-90 mph and it doesn't appear that you have to remove the pan to install it. I remember reading a few years ago that you can change a few things in the 2004R and use a th400 kick down wire to control it, but I don't know of anyone that has done it.
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74 GMC SWB Project "Sin-thia" Static Dropped 8"f/10"r http://67-72chevytrucks.com/vboard/s...d.php?t=460030 97 GMC reg cab short bed, 4.3V6 / 5spd, daily driver 220,000 miles, all stock for now |
03-31-2010, 08:38 PM | #15 |
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Re: Adding overdrive to a TH350?
My tranny builder provided a nice TV cable for me so I'm set there. I'll have to look into the B&M lockout options.
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Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken |
03-31-2010, 09:26 PM | #16 |
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Re: Adding overdrive to a TH350?
all maters about gear ratio ,my th350 screams down the highway at 75mph @3000rpm thanks to the 3.42 gears
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Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90 |
03-31-2010, 09:28 PM | #17 | |
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Re: Adding overdrive to a TH350?
Quote:
there are 3 tail shaft lengths available on a TH350. 6", 9", and 12". the 700 is very close to the same length as a mid length tail shaft equipped TH350. the 200 is very close to the same length as the short tail shaft equipped TH350
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03-31-2010, 10:33 PM | #19 | ||
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Re: Adding overdrive to a TH350?
Quote:
Quote:
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04-01-2010, 06:41 AM | #20 | |
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Re: Adding overdrive to a TH350?
Quote:
Forgot all about the different tailshaft lengths.
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74 GMC SWB Project "Sin-thia" Static Dropped 8"f/10"r http://67-72chevytrucks.com/vboard/s...d.php?t=460030 97 GMC reg cab short bed, 4.3V6 / 5spd, daily driver 220,000 miles, all stock for now |
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04-01-2010, 01:23 PM | #21 |
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Re: Adding overdrive to a TH350?
[QUOTE=qu1cks1lver56;3893899]haha 3.42's is what I've got. 75 is about 2700rpm for me. which is great for no overdrive, but I'd really like 3.73's and an overdrive./QUOTE]
how can i test to see if my lockup converter is working ?
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Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90 |
04-02-2010, 02:14 AM | #22 |
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Re: Adding overdrive to a TH350?
only way i know of, is to unhook the vacuum switch, and run down the highway and see if you have any higher rpm's than normal, then hook it back up and see if its any different.
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