atthemattin

I'm going to be building a 450ish hp 383 and i was thinking about doing something about doing something with the tranny. however, seeing how I still have the original th400 and that it can handle a lot of hp. I figured i would just stick with it. I wanted a little better mpg because i plan on road tripping this summer around the US. so i was looking at gear vendors and i was wondering if anyone put one of these in and what they thought? are they worth the money, will the overdrive unit drop the RPMs to under 2k at 60?

Gordonm

Not much of an automatic guy but the Gear Vendors OD is expensive and ver tough to fit in a Vette. I would go with a well built 200R4 or the 700R4. They fit better and can be built to handle that Hp no problem. The cost will be less than a rebuilt 400 and Gear Vendors OD and will fit much better. Look up Bow Tie overdrives. They have what you need.

cv67

With Gordon
GV are super friggin strong and wont break..but will rob some power.

ezobens

Check the dimensions-
I don't think you can fit it in the C3 tunnel without some (or a lot of) cutting. Also, your driveshaft will be fairly short and I don't know if you'll have issues with driveshaft angles afterwards?

Gear Vendors makes a stout unit but they are VERY pricey-
You can buy a 5-speed for what those cost.
They are great in an A or B body that has plenty of room. On a C3, Not so much.
Just my .02

63mako

They are awesome in a motorhome!
Tough fit in a vette. Go with an OD trans.

GRIZ73

I have a GVO unit behind the stock rebuilt Muncie 4 speed on my 1973 big block. GVO works great with stick shift. It is incredibly fun to drive and strong. Big block is 496 full roller that hit 635 on the dyno. The installation only required a little cutting and fiberglass over sponge. C5 seats fit fine. GVO cost was $2900 which is reasonable if you have a transmission to put it behind. I love mine and will do it again on more of my cars.

centralcalvette

I have a GV in my 17000 # Motorhome. Tough as nails, 86K miles and no problems. I wouldn't put one in a Vet due to space limits. I would recommend a 5 or 6 speed trans. My 502 Motor home cruises at about 1500 rpm at 65, I get 12 MPG if I drive normal, 10 if I'm in a hurry. Even if you gain 20% MPG, it'll take a lot of miles to break even. Will you REALLY drive it that much?If you drove 10000 miles a year, and saved 20% in gas, you would save $800 a year in fuel,It would take 4 to 5 years to pay for itself if and only if you drove it that much.

7T1vette

The THM-400 is 'bullet-proof' and can take a LOT of power/torque through it. But, it is a relatively inefficient transmission. For what you want to do, you would be much better off with a 200-4R transmission that is built to take the power/torque your engine will deliver. Most rebuild places can easily supply you with that. And that will also get you the overdrive and lockup functions that will provide you with a 20-25% gain in fuel efficiency on the highway. The Gear Vendor unit will cost as much as exchanging your THM-400 for a 200-4R unit; and with the 200-4R, you don't have to make changes in the trans tunnel to accomodate the GV unit's size.

roscobbc

Tell us more about rear end ratio and rpm at cruise speed etc

GRIZ73

Car is currently in the shop for carb replacement,mounting emergency brake line, and battery cut off. The tach has been working intermittently so I cannot tell you what the rpm readings are. The rear end is 3:36 and would work better at 3:55 or more. GVO allows me to shift from 1st to 2nd to 2nd OD to 3rd to 3rd OD to 4th to 4th OD. Or shift normally to 4th and then into OD. The OD is .78 . Check out The GVO web site for technical info.

SuperBuickGuy

you won't like the pause in the shifting. you have to let off the throttle to shift between OD and DD

what they said above (200 or 700r4), or, if price is no object a 6L60e would be hot ticket (they cost nearly 10k, yes, 10,000 dollars, US)

that said, I'd go with a 4L65e, and control the transmission with a computer. GM has had those transmissions at that HP level, stock, for nearly a decade.

7T1vette

Depending on how they are built, the 200-4R, the 700-R4, and the 4L65 are all comparable. The "E" transmissions are electronic and require a full ECM to manage it.

If you have a non-electronic engine, buying an electronic transmission seems like overkill to me. But, if nothing else, this thread shows you have plenty of choices.

SuperBuickGuy

painless (and others) make a stand alone controler so if you can wire a light, you can wire the controller. Electronic control helps with transmission longevity and makes the transmission quite civilized. Of course, I like knuckle dragging as well as the next guy - YMMV

atthemattin

So I've been thinking going the GVO unit mainly because i'm going to be doing a massive road trip around the US come this summer. I've been thinking i may just build a 383 and getting a GVO so i can save some money on gas and just so i don't strain the motor. but I've been thinking about going with the complete ls1 swop and throwing in the t56. but I'm not to sure if it is a super hard swop out. i'm thinking i might throw around 6k into it for the summer. just trying to figure out my best bet.

Shark Racer

I definitely prefer the feel of the electronic 4L60E/65Es I've driven to the 700R4/4L60s, but I've not yet seen someone adapt an electronic transmission box to a 4M or M4M quadrajet. I'm curious how the TPS would be set up - anyone seen/done this and have pics?

chevymans 77

Not for the trans but for my data logging,

Installing the TPS is easy, you can buy the bracket online

I got mine form Innovate when I bought the LM1,

Neal

Shark Racer

Thanks, I'll take a look.

Richard Daugird

How about aa three year update?

cv67

GMPP pretty sure sells a stand alone controller bet Bowtie Overdrive does also.

I would LOVE to get a 6 spd auto, only way pry me away from a manual.
Nice stall with lockup, always in the powerband. Oh yeah!

BUT at 10k good thing dreams are for free

lurch59

You can buy a lot of gas for what it will cost you to do the upgrade. Just sayin'.......