1980 RPM's

I have a 1980 coupe with an auto transmission & 350 motor. I was
wondering what the RPM's should read on the tach when cruising at 60
MPH. My car is running at around 3200 which seems a bit high & my gas
milage is terrible. I was thinking it should drop down to around 2200.
Could this be a trans problem?
Thanks

I think that the RPM reading is correct. That's the reading I get on my
'80. We would have to go with an automatic over-drive tranny if we
wanted to improve mileage. If I'm not mistaken, you have a 350 turbo
hydramatic automatic transmission...

Enrique

I think that the RPM reading is correct. That's the reading I get on my
'80. We would have to go with an automatic over-drive tranny if we
wanted to improve mileage. If I'm not mistaken, you have a 350 turbo
hydramatic automatic transmission...

Enrique

I have a 79 with the TH350 tranny. The car is documented to get 12 MPG. I
checked mine today. I'm getting 12.1 MPG. Yes, that's terrible by today's
standards. However, it's normal for our cars.

If your mileage is much less than 12 MPG you probably have some tuning to
do. However, I'd bet your transmission is fine.

Ryan

"Jimmy Vette" > wrote in message
m...
> I have a 1980 coupe with an auto transmission & 350 motor. I was
> wondering what the RPM's should read on the tach when cruising at 60
> MPH. My car is running at around 3200 which seems a bit high & my gas
> milage is terrible. I was thinking it should drop down to around 2200.
> Could this be a trans problem?
> Thanks

I have a 79 with the TH350 tranny. The car is documented to get 12 MPG. I
checked mine today. I'm getting 12.1 MPG. Yes, that's terrible by today's
standards. However, it's normal for our cars.

If your mileage is much less than 12 MPG you probably have some tuning to
do. However, I'd bet your transmission is fine.

Ryan

"Jimmy Vette" > wrote in message
m...
> I have a 1980 coupe with an auto transmission & 350 motor. I was
> wondering what the RPM's should read on the tach when cruising at 60
> MPH. My car is running at around 3200 which seems a bit high & my gas
> milage is terrible. I was thinking it should drop down to around 2200.
> Could this be a trans problem?
> Thanks

<< My car is running at around 3200 which seems a bit high & my gas milage
is terrible. I was thinking it should drop down to around 2200...>>
--------------------

What is the stock rear-end gear ratio in that car?

It has always amazed me how people got along with 3.23:1 rears (or
numerically higher) in older musclecars. The engines in these cars (350 CID
and more) produced more than enough torque at 2,000 rpm to keep the car
cruising happily at 65 mph. Having the engines spinning at over 3,000 rpm
at 65 mph is just terrible and totally wasteful.

Shortly after I had purchased a 1976 Trans Am 4-speed (with stock 3.23:1
rear), I immediately swapped in a Richmond 5-speed and 2:56:1 rear end.
This made a HUGE difference... HUGE. Best mod I ever made on any car, ever.
Prior to the trans and rear swap, the 455 was darned near melting down at 75
mph (3,500 rpm+), sucking gas faster than you could imagine. Can't believe
GM sold cars this way, but I guess transmission technology was fairly poor
back then. And then I've seen original GM ads advertising old Buick GS's
and Ram Air GTO's etc with factory 3.73 or 4.11 rear ends (with optional
4.33:1)!!! Pure insanity. This is truly "race-only" stuff. These cars
must have been completely unuseable on the highway. I can't see how a 400+
cube engine could last very long spinning at 4,000 or so rpm with little
load all day long... would surely overheat before long... mileage would
probably be 5 mpg or something, car would be screaming away making loads of
noise and vibration, etc. When GM sold those cars with 4.11:1 rears, I hope
they had warning decals on the dash that read "not for use on highway!!!".

As for your `80 Vette... you may want to consider swapping in milder rear
gears. You will lose a little tug off the line, but your highway experience
will be much more pleasant. What do you have in that car... a 3.55? 3.23?
Maybe swap in a 2.73 or so. If the car was a manual, then you could go the
Richmond 5-speed route which is well worth the fairly high expense. I've
heard of some guys swapping in manual 5-speeds into auto tranny cars... not
too hard if you can get all the manual trans parts (clutch pedal, linkage,
etc) out of a wrecked manual car.

Or... I don't know too much about auto trannies, but aren't there some later
model 4-speed GM auto trannies that might work in your car? If you can get
one with a super low first gear, then you could swap in a 2.56 rear without
losing much tug off the line, etc.

<< My car is running at around 3200 which seems a bit high & my gas milage
is terrible. I was thinking it should drop down to around 2200...>>
--------------------

What is the stock rear-end gear ratio in that car?

It has always amazed me how people got along with 3.23:1 rears (or
numerically higher) in older musclecars. The engines in these cars (350 CID
and more) produced more than enough torque at 2,000 rpm to keep the car
cruising happily at 65 mph. Having the engines spinning at over 3,000 rpm
at 65 mph is just terrible and totally wasteful.

Shortly after I had purchased a 1976 Trans Am 4-speed (with stock 3.23:1
rear), I immediately swapped in a Richmond 5-speed and 2:56:1 rear end.
This made a HUGE difference... HUGE. Best mod I ever made on any car, ever.
Prior to the trans and rear swap, the 455 was darned near melting down at 75
mph (3,500 rpm+), sucking gas faster than you could imagine. Can't believe
GM sold cars this way, but I guess transmission technology was fairly poor
back then. And then I've seen original GM ads advertising old Buick GS's
and Ram Air GTO's etc with factory 3.73 or 4.11 rear ends (with optional
4.33:1)!!! Pure insanity. This is truly "race-only" stuff. These cars
must have been completely unuseable on the highway. I can't see how a 400+
cube engine could last very long spinning at 4,000 or so rpm with little
load all day long... would surely overheat before long... mileage would
probably be 5 mpg or something, car would be screaming away making loads of
noise and vibration, etc. When GM sold those cars with 4.11:1 rears, I hope
they had warning decals on the dash that read "not for use on highway!!!".

As for your `80 Vette... you may want to consider swapping in milder rear
gears. You will lose a little tug off the line, but your highway experience
will be much more pleasant. What do you have in that car... a 3.55? 3.23?
Maybe swap in a 2.73 or so. If the car was a manual, then you could go the
Richmond 5-speed route which is well worth the fairly high expense. I've
heard of some guys swapping in manual 5-speeds into auto tranny cars... not
too hard if you can get all the manual trans parts (clutch pedal, linkage,
etc) out of a wrecked manual car.

Or... I don't know too much about auto trannies, but aren't there some later
model 4-speed GM auto trannies that might work in your car? If you can get
one with a super low first gear, then you could swap in a 2.56 rear without
losing much tug off the line, etc.

'Having the engines spinning at over 3,000 rpm at 65 mph is just
terrible and totally wasteful. '

ME: Not to mention decreased longevity of the motor.

'Having the engines spinning at over 3,000 rpm at 65 mph is just
terrible and totally wasteful. '

ME: Not to mention decreased longevity of the motor.

'I checked mine today. I'm getting 12.1 MPG. Yes, that's terrible by
today's standards. However, it's normal for our cars. '

ME: In my 1970 built BB Vette., i get 13 mpg town and 14.5 highway. 4
speed M21.