Cruising RPM seems too high...
07-07-2019, 08:52 PM
#1
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Car: 1986 Trans Am
Engine: 5.0 LG4 4BBL
Transmission: T5 5-Speed
Axle/Gears: 3.23
Cruising RPM seems too high...
Strange one guys. Took my 89 Bird (Tbi 305) on the highway for the first time. I have 4.10s and a 700R4 with an unknown stall aftermarket TQ converter. Also stock diameter 245/50R16s.
At 60mph I'm at 2350rpm in OD.
Isn't this a bit high, even for 4.10s??? Does a high stall converter affect the RPM range?
At 60mph I'm at 2350rpm in OD.
Isn't this a bit high, even for 4.10s??? Does a high stall converter affect the RPM range?
Last edited by Carlos89; 07-07-2019 at 08:56 PM.
07-07-2019, 10:16 PM
#2
Re: Cruising RPM seems too high...
No, that sounds about right for a .7 4th gear, with a 26" tire and 4.10 gears. Even 3.73s that get recommended frequently are pushing it with the 700R4. 4.10s you're pretty much trading highway cruising for drag strip performance.
07-08-2019, 02:45 AM
#3
Supreme Member
Re: Cruising RPM seems too high...
4.11's are very steep, not a very friendly automatic ratio for daily drivers with any automatic transmission
Even with 3.5's I am complaining about highway RPM and wanting 3.23's
I remember the factory 305TBI had 2.73's behind it's 700R4 and would drop to 1400rpm at 46mph or something
Even with 3.5's I am complaining about highway RPM and wanting 3.23's
I remember the factory 305TBI had 2.73's behind it's 700R4 and would drop to 1400rpm at 46mph or something
07-08-2019, 02:46 PM
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Car: 1986 Trans Am
Engine: 5.0 LG4 4BBL
Transmission: T5 5-Speed
Axle/Gears: 3.23
Re: Cruising RPM seems too high...
Thank you guys I appreciate the info.
BTW, is there anything I can do to test what the stall speed is on my torque converter?
BTW, is there anything I can do to test what the stall speed is on my torque converter?
07-08-2019, 06:22 PM
#8
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Car: 1986 Trans Am
Engine: 5.0 LG4 4BBL
Transmission: T5 5-Speed
Axle/Gears: 3.23
Re: Cruising RPM seems too high...
Ok thanks. I was asking because the converter is blue and the PO replaced many components (rear gears, diff cover, intake manifold, headers and full exhaust, shift kit) so I thought he might have replaced the tq conv as well. He's long gone by the way, so I couldn't ask him.
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