overdrive opinion

[bigmac73]

alright guys lets hear it ...
a built 700r4 for around 2300 to 2500 or spend around the same amount maybe a little less for a gear vendor OD set up for my Th350???

[Dad's72]

Never knew there was an option for OD on a TH350? Is this an aftermarket option when rebuilding?

[bigmac73]

Originally Posted by Dad's72

Never knew there was an option for OD on a TH350? Is this an aftermarket option when rebuilding?

https://www.gearvendors.com/hrgm3s.html

[MikeB]

I'd sure consider the GV unit. Those things are very stout, and you don't have to worry about controlling a lock-up converter. In any gear you can click a switch and it will go into OD, essentially giving you 6 ratios to choose from behind a TH350. Or you don't have to touch a thing, and it will go into OD at some pre-selected road speed and drop out below that.

Please note the GV's .78 ratio won't lower your highway RPMs as much as the 700R4's .70 ratio. But I think .78 is actually a better ratio. It will decrease your highway RPMs from, let's say, 2500 to 1950. That's huge IMO. And you still have the TH350's nice 1st gear ratio, not the crazy low 1st gear in the 700R4.

[un4gvn!]

I installed a Gear Vendors in my 69 CST LB and love it. I even had a one piece drive shaft made. I'm getting better miles to gallon too.

[MikeB]

Originally Posted by un4gvn!

I installed a Gear Vendors in my 69 CST LB and love it. I even had a one piece drive shaft made. I'm getting better miles to gallon too.

TH350 trans? How do you use the OD? Auto-engage at xx mph or???

[HO455]

I have a GV on my Burban with a TH350. Works great. I use the GV controller and it shifts into OD automatically at 40 mph.
If your not in a hurry they come up used regularly. Over the years I have bought 3 of them. One for $1300, one for $600, and one for $50.
Link to my GV installation. Scroll to post 642.

http://67-72chevytrucks.com/vboard/s...698377&page=26

[Sheepdip]

I have 2 GVendors 1 behind a TH350 and 1 behind a SM465 both perform flawlessly.

[Sheepdip]

Originally Posted by Dad's72

Never knew there was an option for OD on a TH350? Is this an aftermarket option when rebuilding?

You pull the tranny tail shaft housing and bolt the GV Unit up where the housing mated to the back of the tranny ...very easy install.

[Sheepdip]

Originally Posted by MikeB

TH350 trans? How do you use the OD? Auto-engage at xx mph or???

Both of my units use a speed generator driven off of the speedo cable that signals the controller with voltage as to when to engage or disengage.

[Accelo]

Sorry, I am voting for the 4l60. Or 700r4 if you prefer.
If you add the overdrive to the 350 you still have a used transmission.
You can split shift with the GV unit but who does that except for heavy loads?
I just think it keeps it simpler.
Rick

[davischevy]

I have a 700R4 in my Longhorn behind a big block. I also have a new GV in the box and the now fresh 400 turbo that came out of the truck.

lf the 700R4 ever bites the dust, I will put the turbo 400 and GV in it.

[MikeB]

Originally Posted by Accelo

Sorry, I am voting for the 4l60. Or 700r4 if you prefer.
If you add the overdrive to the 350 you still have a used transmission.
You can split shift with the GV unit but who does that except for heavy loads?
I just think it keeps it simpler.
Rick

Valid point about the 700r4 being a simpler solution. I guess its biggest issue is initial TV cable adjustment. And it goes beyond making sure there is zero slack at idle! If a non-OEM carburetor doesn't have the proper geometry-corrected throttle lever, there will be either slop at idle, or the carb won't go to WOT. And even with the lever, you must make sure the valve travels to its stop at WOT, or line pressure will be too low. With specific Q-jets and throttle bodies it shouldn't be a problem, because they were designed to work with the 700R4 and 2004R.

Not only that, but once the TV cable is correctly adjusted, any carburetor idle speed adjustment that you may have to do periodically (like winter/summer) requires a re-adjustment of the TV cable. But again, with EFI, it shouldn't be an issue.

I doubt that most transmissions shops understand the above unless they are familiar with non-factory type installations

On another note, how do you feel about the ratio spread between 1st and 4th gear and then converter lock-up? On a friend's car, a 37 Chevy with a 350, 1st gear is so low that the 1-2 shift happens after a couple car lengths. 4th gear seems too tall, especially when the converter locks-up. In fact, he keeps the shifter in 3rd gear until he gets on the highway, and controls lock-up with a dash-mounted switch. But again, all that may be due to not having a vacuum switch to control the trans, and whatever else a stock installation has. His car has a 3.36 axle and 29" tires.

[bigmac73]

If you add the overdrive to the 350 you still have a used transmission.


what does that mean "Used"??
I built it myself and not worried about it being used and works great only got about 3500 miles on it ...

I think i will go with the GV unit , I am not interested in the whole split shifter idea just the OD function on the innerstate.

[Bigdav160]

That's why I chose a 4L60. I could buy cores for less than $200 and rebuild them myself

[72c20customcamper]

GV without a doubt specially if you do any towing I burned up two 700r4s on my 87 Suburban back in the 90s . First one the original at about 90k , I had bought the truck with 65k and it never towed prior to my ownership. Replaced with a goodwrench rebuilt with the upgrades ,that one lasted to 155k . I sold it after the second one was replaced and bought a new 2500 Savanna 12 passenger van in 98 . That towed till I bought my Dodge in 07 without a problem .

[SCOTI]

Originally Posted by MikeB

Valid point about the 700r4 being a simpler solution. I guess its biggest issue is initial TV cable adjustment. And it goes beyond making sure there is zero slack at idle! If a non-OEM carburetor doesn't have the proper geometry-corrected throttle lever, there will be either slop at idle, or the carb won't go to WOT. And even with the lever, you must make sure the valve travels to its stop at WOT, or line pressure will be too low. With specific Q-jets and throttle bodies it shouldn't be a problem, because they were designed to work with the 700R4 and 2004R.

Not only that, but once the TV cable is correctly adjusted, any carburetor idle speed adjustment that you may have to do periodically (like winter/summer) requires a re-adjustment of the TV cable. But again, with EFI, it shouldn't be an issue.

I doubt that most transmissions shops understand the above unless they are familiar with non-factory type installations

On another note, how do you feel about the ratio spread between 1st and 4th gear and then converter lock-up? On a friend's car, a 37 Chevy with a 350, 1st gear is so low that the 1-2 shift happens after a couple car lengths. 4th gear seems too tall, especially when the converter locks-up. In fact, he keeps the shifter in 3rd gear until he gets on the highway, and controls lock-up with a dash-mounted switch. But again, all that may be due to not having a vacuum switch to control the trans, and whatever else a stock installation has. His car has a 3.36 axle and 29" tires.

Most vehicles that are 'not stock' prob don't need OD until they're actually on the highway. That '37 Chevy you mentioned is only @ 1750/45mph & 1950/50mph. He has no need for 4th gear in town.

Heck, the math says that combo is only moving along @ a tick over 2700 @ 70mph in 3rd so that 700r4 puts him kind-of under the target zone of a traditional warmed-up sbc @ just under 2100rpm @ 75mph unless it's a low rpm/torque built motor. For C10's, I'd want minimum 2200rpm & be good w/24-2500 @ ~75mph.


As far as 700r4 vs. a 3spd auto/GV OD for someone that doesn't personally have experience with/or 'have a 'guy' for transmission builds? I'd do the GV for fewer headaches & better rpm splits between gears.

You're likely to spend the same amount (well built 700r4 vs GV) on initial purchase unless you build one yourself so that's a wash. The finicky TV cable adjustment is always a concern when poking around under the hood (not a big deal on the average Joe/Janes all-stock/EFI'd mass produced set-up). Not that the GV doesn't have it's drawbacks though (don't put it in reverse when it's engaged or it will be done). The GV gets the nod for strength when OD is engaged.

[gmc684x4]

Need the ecm i am going 4l80e tougher tranny
With some sensors added a stock ecm /pcm you can add it to a carberated truck
I seen a few threads on this setup I never fully followed up as I am going fuel injected on the trucks that are getting the slush box

As for a 700r4 depends on how you drive
Drive it hard and spirited may want to look at a tougher tranny take easy and mall crawler it should last a decent amount of time you also need to consider the torque output you have this is the reason why gm never put a 700r4 behind a big block

['68OrangeSunshine]

Would a Gear Vendors OD work in a '67 K/10 Suburban w/ TH350/NP205? Or are you only considering 2WD here?

[SCOTI]

Originally Posted by gmc684x4

Need the ecm i am going 4l80e tougher tranny
With some sensors added a stock ecm /pcm you can add it to a carberated truck
I seen a few threads on this setup I never fully followed up as I am going fuel injected on the trucks that are getting the slush box

As for a 700r4 depends on how you drive
Drive it hard and spirited may want to look at a tougher tranny take easy and mall crawler it should last a decent amount of time you also need to consider the torque output you have this is the reason why gm never put a 700r4 behind a big block

If going w/a factory trans set-up, this would be my first choice. 4l80e that's controlled/tuned via the TCU. I've been looking for a budget/stock take-out for my dually but they command top price even for used units in my area (DFW TX).

[gmc684x4]

I got mine for free it came with a van with a blown intake gasket
Pick a parts craigslist facebook marketplace are the kind of places to look for a deal 2500 3500 vans can be the easiest to find as they should have a 4l80e in the vans there less motor dependent

[Accelo]

[QUOTE=SCOTI;why gm never put a 700r4 behind a big block .[/QUOTE]

GM didn't do it but I did. Never had an issue. Big changes on two fronts. Fuel mileage went from 10 to 13 on the highway a 30% improvement. The noise in the cab dropped significantly. I was amazed at how much noise came from the motor.
Rick

[davischevy]

Originally Posted by '68OrangeSunshine

Would a Gear Vendors OD work in a '67 K/10 Suburban w/ TH350/NP205? Or are you only considering 2WD here?

Yes.

[davischevy]

We have two 700R4 behind big blocks.

[HO455]

A couple of points on the 700r4.
If your looking to maximize fuel mileage the 700r4 has an edge due to the lock up converter.
To improve the life span of the unit only shift it into overdrive on the highway above 45 mph for distances longer than a mile. When the transmission is continually shifting in and out of OD extra heat builds up to the detriment of the transmission. 700r4s are prone to hunting when driving in the 35 to 45 mph.