I have a 68 Camaro, I took it to the transmission guy today. I don't like the way it's rpms are too high! It feels like when I am on the highway its n 2nd gear. I want a cruiser with an overdrive transmission (700r4). The transmission guy said the changing out my 400 turbo transmission to an r4 would give me a more smoother ride and lessen my rpms allot. He also stated that the gear ration was low.. Around 280 I believe. My question is... Would changing only the gear ratio to whither number lessen the rpms... Giving me a quieting and less of an engine rev, or should I put in the r4 transmission?

 

What gears do you have in the differential, ? And which differential. Early 10 bolt or 12 bolt.And since you want make it a cruiser and keep your Turbo 400 .You can go with 3:31 or 3:73 gears,with a 26" tall tire.Or if you go with a 8.5 10 bolt with 3:42 gears.It will cruise at 2500 -2800 RPM at 60 MPH.its all up to you.

 

26 " tall tire?? I have 18 inch rims...if I can get that 2600 rpm and 60 I will stick with the gears ....it will save me money...thanks!

 

With gears you give up one thing to get another. When you move to a low ratio and taller tires you give up your low end power. Higher ratio gears are one of the first upgrade people do to make their car faster stop light to stop light.

With the 700R4 you have improvement when Launching and the 4th gear which will allow for nice highway cruise and better MPG. If you made me drive a 60s or early 70's Stock Camaro and told me I could only do one upgrade, It would be a Overdrive trans.

Check out Gear Vendor's Overdrive addon for the TH400. Still not as cheap as a gear change but it is another option.

 

Hmmmm so with my 18s on there, the gear ratio wouldn't matter that much... So I think I will go with the 700r4 and go with a higher gear ratio later... The higher the gear ratio the better as far as cruising and lower rpm, correct?

 

You can run a 3:31-373 gears and still cruise at a reasonable RPM.You can still have a 26"-27" tall tire even with 18" rims. Thats what an overdrive is for.And it lets the engine get in its "sweet spot"for a compromise for fuel economy and power, My 1979 Z-28 RS Camaro Pro-Touring car has a 500 HP Supercharged 377 cubic small block Chevy,With a Super T-10 4 speed ,3:42 gears,17x8 wheels with a 17 inch tall tire,Gets around 22-24 MPG on the highway cruising at 24-600 RPM at 60 MPH. My 1981 El Camino SS daily driver.Also Pro-touring truck.With a 290 HP 350 crate engine with 3:42 gears ,same size wheels and tire does about the same.Its all the matter of combinations.

 

Better first gear 3.06:1 700r4 vs 2.48:1 Th400. So you will not only retain your current launch it will be better. Like all non-overdrive transmission your th400 has 1:1 ratio final drive. The 700r4 has overdrive which is 1:0.7. Meaning what ever RPMs you have now just times it by .7 and that will be your final drive.

If you are doing a cost review and you are not doing the work yourself The price of a rear gear swap, rims and tires and speedo recalculation. I assume your mechanic quoted you installed/with shifter/cable/cross member and drive shaft mod.

Now if your car is numbers matching then by all means don't do this, but other then that it will increase the value of the car. Adding gears is always a good idea in a general purpose car. I cruise at 80 MPH and I m doing 2500 RPMs in my 2000 z. Since it is my daily driver I do this 1/2 hour at a time. My 67 is not a daily driver and rarely sees the highway and I still have a T56-6 speed sitting next to it not sure if I want to install it or not. When you look at modern car 6 and even 8 speed automatics are common now.

I am an older guy and I had friends that said their 2 speed power glide was all they needed. The new 3 speeds are over kill, just add more power. I even knew a mopar guy that loved his 3 speed manual trans.

 

All I am looking to do I'd decrease the rpms while driving, that's why I'm going with the 700r4. I'm just hoping when it's complete I won't have to change the gear ratio. My mechanic says it will be a noticeable difference.

 

We know almost nothing about your car. If you drive the speed you want to cruise at then look at the RPMs. Times that number buy by .7. So if your car is running 3000 RPMs at the speed you want to drive. 3000 X .7, With the 700r4 you will be doing 2100 RPMs.

What you need to be sure of is that your motor runs well at the lower RPMs. If the motor has be modified if my not run well below 1800 RPMs If the gear change put you under the that point then it could be a problem. You should go out now and drive the car at you calculated RPMs in 3rd gear and see if it seems happy.