The Stovebolt Site Forums The Shop Area Engine Shop 700r and 3.08 rear end

First of all, thanks for the responses as they have shed some light on my questions. I have a question for those who know a little more than I do about matching up transmissions and rear ends. I purchased a 69 camero posi with 3.08 gears and still want the 700r for the 4th gear. Just wondering if someone in here can tell me what to expect...other than the gas mileage.
I am way too old for burning the rummer off and just want a cruiser.

Thanks,

Steve in Idaho

I think you want at least a 3:42 or better yet a 3:73. With the 7004R's overdrive a 3:08 will cause poor driveablility and cause the motor to lug at highway speeds.

I just talked to the rod shop guru and his trans guy. Rod shop guy says not too good and trans guy says it's ok. So far it's two to one. Thanks Don

Steve

I vote for the 3.08 but it depends on what engine you are running. I have a 700-4R in my 70 pickup with a stock Goodwrench 350. It works real good. It runs good down the highway. There is one long hill on the interstate that if there is a headwind & I have the air on it will downshift or I usually downshift manually before it labors.

Do you have 3.08 gears in your truck?

Forgot...got a rebuilt factory 283 that I am going to slap an edelbrock performer and a cfm 600 to the top soon with the electric choke. Be a little better performer.

Sorry I meant to mention that. A 283 won't pull that much gear. You are just as well off with a TH350 trans. or change to 3.73 or 3.90 rear end.

3.08 is too much gear for the 700r4. You would be better off with a TH350 or 400. A shift kit and an overdrive module might help, but I doubt it. Better off with a 3.73 or 3.42 gear if you plan on using the 700R4.

I would use 3.73 gears with that 700r trans, rpm at 65 mph. should be right around 1800 to 2000 rpm depending on tire height.GOOD LUCK.

I must comment that the factory put higher gears than 3.08 behind the 700r4 in some applications. I have a 2.73 rear out in my shop from a car equiped with a 700r4.

Without knowing both the motor and how the truck will be used I don't know how you can answer a question like this one. And you need to know more than just the size of the motor, the cam and induction are going to be part of the equation. A mild cam and EFI means the motor will run smooth at a pretty low RPM and with the OD might give you fantastic mileage running down the highway. A bumpy cam and tunnel ram are going to mean different answers.

An automatic overdrive does not need to stay in overdrive all the time to work right. Its not the same as a manual where you need to shift it yourself when things get a little harder.

A carburated 283 pushing a pickup through the air I'm inclined to agree the 3.08 might not work real well. But if you were talking a 388 stroker or something like that, I'd say go for it.

I have a 5000 pound four-wheel-drive pickup with a TBI 350, 700r4 and 3.42 gears that works pretty good empty. It does not pull a loaded trailer with the finesse I'd like but based on how it performs I'd expect a 3500 pound 1/2-ton to move pretty good with similar equipment. And many of the factory 1/2-tons have 305s with a 700r4.

A properly setup 700r4 is going to shift from OD to direct when it hits an incline and needs the gears. But running down the highway in OD if the motor runs smooth and clean you're going to get great mileage. Press the accelerator and you'll downshift.

I am running a 700R4 in my 52 with 4:10's and I am pretty happy with it. It has great street manners, pulls well and cruises very nice on the highway. If you haven't purchased the tranny yet Langdon recommends the 200R4. I can't remember the reason but I had already made my purchase when he told me that. You might want to give him a call.

I worked at a Chevrolet dealership in the early 80's when the pick-ups started showing up with the automatic overdrives, the 1/2 ton pick-ups only came with a 305. They had a ton of transmission failures. The engine wouldn't pull in overdrive and transmissions kept going bad. They soon discovered that they needed a minimum of a 3:42 ratio with a 3:73 being the preferred ratio. This was in Minnesota / Wisconsin area anyway. We had a fair amount of hills and this does make a difference. Just my opinion with a 283 I would either put more gear in it or go with a TH350.

well hear this.I'm running a chevy 51,1/2T.RUNNING A 350CI with a700r4 tranny,9" ford rearend.the gears are 3.00 from a 64 fairlane.brought the electronic box so the tranny shifts properly.I use it for car cruises.Live in Pa,gone to Datona 3 times. RUNNING a RV cam,4barrel 600cc edilbrock.the gas milage is great on a trip 22 to24 MPG.at1800 rpm,s im kicking 85mph.had it up to 130MPH.In town 18mpg.So I say yes to the 3.08 gears.check out the gallery photo's 51 chevy.dan kalenak.subframed with a 79 camaro front clip.also running a duel plane intake.HP comes to around 365.good luck an watch the price of gas in the future

I'm not debating the fact that in some cases a overdrive transmission will work with less gear ratio. As George said earlier and I was saying, a motor with less cubic inches or horsepower will have a harder time with this set-up. Its all about driveablility.