transmission question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

lofat · 05-07-2003, 02:03 AM

t350c - no over drive?

what is the point or should i say purpose of no over drive?

forgive the newb question - it is jus strange to me as i have never owned an automatic with no od.

thanks,
scott

79BIG10 · 05-07-2003, 02:09 AM

Correct. TH350, TH350C (save as Th350 but with lock up converter), and TH400 do not have OD. THe 700r4 and later the 4L60E (electronic 700R4), and 4L80E all have OD. The early model 700r4's (pre 87-88) were not the best. The more desireable ones are the 87+ models. In 93? the 700r4 became the electronic versions and thus the 4L60E came to be.

The point in having one is better gas mileage through lowering RPM at the same speed. For instance if you're cruising at 70MPH with a TH350 and a 3.07 rear end you're at about 2200RPM. Now with a OD tranny you are at about 1800RPM or so. This saves gas, wear and tear since the engine is not revving as high to keep up speed.

lofat · 05-07-2003, 02:13 AM

so having the OD will save me gas - are these a fairly easy switch out?

i was shocked the first time i took it out on the freeway and stomped it and it didn't just downshift and boogie. you should have seen me - i was checking under the floormats making sure nothing was obstructing the pedal from going all the way down. :p

rockman20 · 05-07-2003, 09:22 AM

The 350 and the 400 are nice transmissions. Smaller, cheaper to rebuild, and used a lot in race cars. For a car or truck that never really sees the interstate, these transmissions are fine.

But in cases where you do a lot of highway traveling, OD is very nice to have. My truck has the 700R4 and around town I only drive it in 3rd. So I don't even use OD unless I am out on the highway traveling around 55 or above.

For an idea of cost, I had my entire TH350 rebuilt in my Cutlass with a new, stock, rebuilt, torque converter for about 700 bucks. My dad had his 700R4 in his van rebuilt with no torque converter and it cost him about 1,300 bucks. Granted his is a bit beefier since it lives behind a 6.2L diesel in a 3/4 ton conversion van, but you get the picture.

To upgrade from a TH350 or a TH400 to an overdrive isn't all that hard. But you will need to shorten the driveshaft, move the transmission crossmember, and wire in a circuit for the lock up torque converter. So it's not just a direct bolt in.

05-07-2003, 02:03 AM	#1
lofat Rollin' Member Join Date: May 2003 Location: Hayward, California Posts: 240	transmission question t350c - no over drive? what is the point or should i say purpose of no over drive? forgive the newb question - it is jus strange to me as i have never owned an automatic with no od. thanks, scott

05-07-2003, 02:09 AM	#2
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,775	Correct. TH350, TH350C (save as Th350 but with lock up converter), and TH400 do not have OD. THe 700r4 and later the 4L60E (electronic 700R4), and 4L80E all have OD. The early model 700r4's (pre 87-88) were not the best. The more desireable ones are the 87+ models. In 93? the 700r4 became the electronic versions and thus the 4L60E came to be. The point in having one is better gas mileage through lowering RPM at the same speed. For instance if you're cruising at 70MPH with a TH350 and a 3.07 rear end you're at about 2200RPM. Now with a OD tranny you are at about 1800RPM or so. This saves gas, wear and tear since the engine is not revving as high to keep up speed. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

05-07-2003, 02:13 AM	#3
lofat Rollin' Member Join Date: May 2003 Location: Hayward, California Posts: 240	so having the OD will save me gas - are these a fairly easy switch out? i was shocked the first time i took it out on the freeway and stomped it and it didn't just downshift and boogie. you should have seen me - i was checking under the floormats making sure nothing was obstructing the pedal from going all the way down. :p __________________ :: 1977 C10 cheyenne :: :: 1973 new yorker brougham :: for sale - $1,500 lofat productions

05-07-2003, 09:22 AM	#4
rockman20 "The dude abides" Join Date: Apr 2003 Location: North Dakota Posts: 472	The 350 and the 400 are nice transmissions. Smaller, cheaper to rebuild, and used a lot in race cars. For a car or truck that never really sees the interstate, these transmissions are fine. But in cases where you do a lot of highway traveling, OD is very nice to have. My truck has the 700R4 and around town I only drive it in 3rd. So I don't even use OD unless I am out on the highway traveling around 55 or above. For an idea of cost, I had my entire TH350 rebuilt in my Cutlass with a new, stock, rebuilt, torque converter for about 700 bucks. My dad had his 700R4 in his van rebuilt with no torque converter and it cost him about 1,300 bucks. Granted his is a bit beefier since it lives behind a 6.2L diesel in a 3/4 ton conversion van, but you get the picture. To upgrade from a TH350 or a TH400 to an overdrive isn't all that hard. But you will need to shorten the driveshaft, move the transmission crossmember, and wire in a circuit for the lock up torque converter. So it's not just a direct bolt in. __________________ RockMan 1993 Chevy Silverado C3500 1 ton dually 1994 Honda Civic 1969 Oldsmobile Cutlass S 1953 IH Farmall Super M New to the fleet: 1992 Subaru Loyal



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