HawkZ28

iTrader: (2)

I took the car out for the first time in a while today, and remembered I meant to ask this last year, but got side tracked with things like replacing wiring, lights, oilpan gasket, etc....

On my way to the office, I noticed that my car turns (at 70mph, checked via GPS) about 3250rpm, and almost 3500 at 75mph.

700r4 w/ the following mods:
.500 boost valve
vette servo
B&M shift kit
summit/tci lock up 2k stall converter

For lockup, I'm using a on/off switch. When it locks, it only brings the rpm's down 1-200, depending on the amount of throttle I'm giving it.

Fluid is full, and fresh. I don't know my rear end ratio for sure, BUT I do know it's either a 3.42 or 3.73. Tire size is stock 245/50/16.

All that being said, does that seem awfully high to you guys? I seem to remember my 83 w/ 3.23's only turning around 2750 at around 80mph, give or take 3mph.

camaronewbie

Mine's running the same as yours - I have identical setup as yours (my gears are 3.42). Most folks say the rpms are too high, but everything is working, so I don't know either. BTW - mine's been this way for 3 years now.

85MikeTPI

iTrader: (2)

At 3250rpms you should be close to 95mph... Something ain't right...

built91Z28

Dumb question but have you counted the shifts to make sure its actually in 4th and not still in 3rd?

TMFK

My car turns 2000 rpm at 60 with the converter locked. So 75 would be 2500. Thats with 3.73s and 26.1 in. tall tires. Sounds like its not going into 4th.

85MikeTPI

iTrader: (2)

http://www.f-body.org/gears/

Sounds like 3rd gear to me..

HawkZ28

iTrader: (2)

Sorry, I was off. I am at closer to 3k at 70, 3500rpm at 80. I realized I was off in my post on the way home

Counted shifts to make sure it was in 4th.

I took a pic on the way home doing 80, and it's sitting right at 3500rpm (factory tach). That was w/ the converter locked.

Even when it's locked, if I give it gas, there's no fluctuation in RPM up, or down when I lift off.

Another thought- my tach couldn't be off that much could it?

Gallileo60

Don't mean to thread steal, but what does the boost valve do????
My car with 3.23's turns more than that according to the factory tach (Which could be off)..Thanks for the reply...Tom

Gregzz4

I'll agree....something is off

In my truck I run 28" Tires and with a 3:42 and lockup engaged I get about 16 or 1700 RPM @ 70 or 80 MPH on a flat stretch

I haven't nailed it down exactly, but it sounds like you are off

$750 L98

IF it is indeed going into OD, and the motor sounds like it is actually doing 3,000rpm@70mph...tell me something, how do you like the 4.56 ring and pinion? lol

I have a 3.73 ring and pinion and turn just a hair over 2,200rpm@65mph. Either you lost overdrive, you have a 3 speed instead of a 4 speed, or if your car has always been this way - some one stuffed a 4.56 rear in there. I'd lose my mind cruising the highway at those RPMs

blue85305

3200 rpm isn't that bad, but as someone already said if using the factory tach they are known to be off.

HawkZ28

iTrader: (2)

I'll have to do a vid.....you can see and feel it grab all the gears. The rear end was from a donor, but which one I honestly don't recall. If it's the one I *think* it is from it was an 83 Z28 that a buddy had.

I like the sound at 3200, but it does get old- my office is 52 miles of interstate away. So I do like the wife and turn the stereo up

BTW, boost valve increases the line pressure= firmer shifts.

HawkZ28

iTrader: (2)

Here's the videos. Sorry for how shakey they are.

On a side note, I knocked down 19.7 mpg.....I drove about 134 miles, and put 6.8 gallons in this morning.

The first vid is leaving the bank on the way out of town. The 2nd and 3rd are after I hit a 75mph zone, and was running 80mph or so. THANKS again in advance!

http://www.youtube.com/watch?v=36jeVnK3-Ik

http://www.youtube.com/watch?v=Og1fi...eature=channel

http://www.youtube.com/watch?v=Lqbsw...eature=channel

blue85305

If you like the sound don't worry, but the only real way to know is to pop the cover and check the gears.

$750 L98

weird, that doesn't sound like 3200rpm. My van with a TH400 cruises at about 32-3500 with 4.10s doing 65 or so and it screams. Your car sounds just like mine cruising along at highway speeds (3.73, LQ9, 4L60E)

HawkZ28

iTrader: (2)

I'm glad you pointed that out- I agree. I was watching the tach more today just driving through town, and according to the tach, at medium throttle, I'm shifting at 4500+, almost 7k at WOT.

Between my gas mileage, sound, and shift points, I'm thinking my tach is a liar, or at least the signal it's getting is.

TMFK

I agree. The engine sound doesn't match the tach at all.

musclecar70sfan

iTrader: (1)

especially with close to 20 mpg.

camaronewbie

OK - now you guys got me wondering about mine - so for the sake of arguement ...

700R4, TC that stalls about 2100rpms, 3.42 rear gears that have been verified with the cover off

I know I'm in 4th - can't help but be able to count the shifts with the shift kit. And I see the TC lockup - I can see the rpms drop about 400 when I flip the switch, and I can actually feel the difference in accelleration when it's locked, and if I come to a stop with it locked, the car starts to buck below 35mph - so I know it's locked. And I rechecked again - at 65mph I'm running between 3k and 3100 rpms.

So - assuming I'm in 4th, and TC is locked - is the only conclusion is that the tach is not correct? Or is there any other issue that could cause this?

HawkZ28

iTrader: (2)

Some thing that i just thought of. Do you have that little cylinder looking resistor/filter on your tach line? Maybe its messing up our tachs......?

built91Z28

I agree with everyone else. That does not sound like 3200-3400 rpm's. I personally dont trust the factory guages at all. I know when I first got my Camaro going I still had the factory guages (well the coolant temp, voltage, gas guage at least). I then put in all Auto Meter guages and my coolant temp went up by almost 20 degrees. I trust the Auto Meter guages more than the factory ones.

joeblue83

iTrader: (8)

with my 3.90 gears and a lockup converter, at 70mph I am going 2350rpm

$750 L98

I'd certainly check the resistance and see if it is still within spec. If it's not I could see the tach reading high. You can use a multimeter to check Ohms on it, not certain what the stock resistor is in a camaro of that year, but the resistor should have an Ohm value listed on it.

HawkZ28

iTrader: (2)

I put that on the 'to do' list for this weekend. I checked up on some threads last night about the tach reading off or high. Wish I had a 90-92- there is a clear as day fix for it. I didn't see a single person with a 82-89 V8 tach that had a fix yet (for longer than 15 miles), only the V6 tachs it seemed.

THANKS again for all the help fellas!

Blind Driver

Incorrect. Jack up the rear and count the revolutions of the tire compared to the driveshaft.

Gallileo60

Mine says the same thing....It shifts around 7k (WOT) 4500 just shifting normal...Tach must be off......Strange how it could be that far off tho....

HawkZ28

iTrader: (2)

So, does this actually sound like 600 rpm idle? On my tach in the car, it says I'm at almost 1200rpm IIRC. I'm at a loss as to what anything sounds like, since this is the first time I've driven the car in over a year, and obviously my tach's been off for a LOT longer than that.

http://www.youtube.com/watch?v=YYOhLXjU_M0

Ca[maro]88

iTrader: (2)

well if you have a buddy with a tach, or you can go buy one from auto store (cheap one) for like 30-50 bucks, and plug it in and take it for a drive. see what rpms are then. im seriously betting your tach is wrong. my tach was way wrong when i got it. 50 mph at 7K? yeah right so i went and got a new tach (good tach) and it read at 60 mph i was going 1700 rpm. 2.73 gears. when i got 3.23 it went up to 2-2100. but i was still gettin 14 mpg with the 2.73 gears. idk how. everybody told me to quit drag racing, with a 305 carb'd and 2.73 gears only thing im drag racing is shopping carts.

$750 L98

Tach is definitely off. My car idles at 950rpm and yours certainly sounds like it's lower, about 650-750rpm.

HawkZ28

iTrader: (2)

Thanks! I wanted to make sure that the dwell/tach meter wasn't off too.....it's one that my dad gave to me a couple years ago that he used on his Chevelle's and Broncos (and it's older than me), but since he doesn't even change his own oil anymore, he thought I'd get more use out of it. First time I used it was last night!

I'd go and get a new one, but my 'lifetime warranty' alternator that I bought 12 years ago just took a dump this a.m. When I get back to town, I need to hit Advanced or Speedway Motors to get another since I can't find the receipt. Wifey said that was ok (I think it means it doesn't interfere with her shopping budget).

I'm going to try and fix my tach sometime this weekend I hope. Need to hit Radioshack and get a potentiameter, or whatever it's called so I can determine correct resistance and re-solder a new capacitor onto the PCB.