vannatte

iTrader: (3)

I just got 3.73's installed in my car and the RPM's seem to be much higher than they should. I have an auto and at 50 I'm at 2000 rpm's and at 70 about 2800 rpm's. Does this seem correct? I reprogrammed the computer with my Hypertech programmer, but maybe I did something wrong?

fccs

iTrader: (26)

That sounds like the mph for 4.10s lol? Are you sure you have 3.73s and didnt get 4.10s by accident or something ahaha.

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

Check there for what you should be at, although I have 3.42s and my speedo reads as I have 3.73s.. so im not sure how accurate that is either. In 6th gear at 80mph im at 2000rpms, I should be at 1800rpms

vannatte

iTrader: (3)

I bought the rearend used and was told it had 3.73's in it. It didn't think to count the teeth to confirm that they were in fact 3.73's. I'm sure they are though. I'm just wondering if it isn't something in the programming?

01ssreda4

iTrader: (96)

with 3.73s in an auto, 70 mph brings about 2500 rpms. Is your converter locking up?

billymz28

put the car on jack stands and in nuetral and count the how many times the driveshaft turns for one wheel turn. That will tell you what gears are there

vannatte

iTrader: (3)

I guess I'm less concerned about what gears I have and more concerned if there is a problem. How would I know if the converter is locking up?

OddballLt1

iTrader: (1)

When your converter locks, your rpms will fall slightly but it will feel like the car is really responsive. Basically you can no longer slip the converter with it locked up. Normally unless its changed, your converter locks at 45mph.

01ssreda4

iTrader: (96)

^^^ thats true, you can count the gear changes. 1-2, 2-3, 3-4, 4-lockup with about a 400 rpm drop. Lock-up particularily happens when you reach good cruising speed and start lifting throttle to maintain speed.

vannatte

iTrader: (3)

Changing the tire height to 25.75 seemed to make a big difference. Now at 50 mph, I'm at about 1800 rpms. I also adjusted the shift points and that seemed to help it shift better.

jimbo98z

iTrader: (3)

It will be hard to tell 3.73's from 4.10's doing that. You're talking about measuring a difference of about 90* of rotation when there's about 30* of free play due to lash...

the_merv

iTrader: (88)

^^If you have 30* of play due to lash then you are missin some teeth..lol



Put it on Jack Stands..mark the Drive Shaft where you can see it from where you spin the Tire. Start spinning and if the Mark comes around a little over 4 times then it's 4.10's.. if it came around roughly 3 3/4 times then it's 3.73's.

BlackScreaminMachine

iTrader: (17)

Agreed, My father-in-law refused to beleive he had 3.23's in his 340 Dodge Demon and I made him count the driveshaft and tires and it was 3 and approx 1/3rd turns. I had figured it out based on his MPH and Tach (Sun Guage which as an old school accurate guage).

I thought it was kinda funny.

itsslow98

iTrader: (18)

i was pulling 2800-2900 rpm at 70 with 4.10s in the 10 bolt and a 3600 stall.

the_merv

iTrader: (88)

Mine at 75 with 3.73's was at ~2700 with stock tires.