Cruising RPMs with stock 700R4, stock tire size, 3.73's?
04-12-2009 | 02:19 PM
#1
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Joined: Oct 2001
Posts: 646
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From: Sedalia, MO
Car: 1991 Z28 vert, 1988 GTA
Engine: 305 TPI, 305 Carb-finally runs!
Transmission: TH-700R4/BW WC T-5
Axle/Gears: 3.73 posi 4th gen 10-bolt/BW 9 bolt
Cruising RPMs with stock 700R4, stock tire size, 3.73's?
Anyone here have any info that can help me? I have a 91 Z28 vert with a 4th gen rear that has 3.73's. The trans is a stock 700R4 and the rims are the stock 16x8 91-92 Z28 wheels, and the tires are the stock size. On the highway, I have to be pulling around 3000-3500 RPMs to go the speed limit. This doesn't seem right, the OD seems to be working. Could by TCC lockup be shot, maybe a new solenoid or converter? If anyone has dealt with this before and can help I'd appreciate it, thanks!
04-12-2009 | 06:28 PM
#2
Senior Member
Joined: Mar 2007
Posts: 574
Likes: 2
From: Muscatine IA
Car: 91 Firebird Formula
Engine: 383
Transmission: built 700r4
Axle/Gears: 4.11, 9inch
Re: Cruising RPMs with stock 700R4, stock tire size, 3.73's?
ive got 3.73 in my 91 formula with 245/50/16's and im goin down the road at around 2000 at 55 and 2500 around 70
sounds to me like your only in third or maybe second. a tcc is only gona effect a couple hundred rpm say 2000 to 1800
sounds to me like your only in third or maybe second. a tcc is only gona effect a couple hundred rpm say 2000 to 1800
04-12-2009 | 06:29 PM
#3
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Joined: Feb 2005
Posts: 475
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From: California
Car: Pontiac
Re: Cruising RPMs with stock 700R4, stock tire size, 3.73's?
go to www.f-body.org/gears/ and make a selection. if your cars not in there you can feed it manually.
04-13-2009 | 01:03 PM
#4
On Probation
Joined: Oct 2008
Posts: 6,319
Likes: 18
From: Northern Utah
Car: seeking '90.5-'92 'bird hardtop
Engine: several
Transmission: none
Axle/Gears: none
Re: Cruising RPMs with stock 700R4, stock tire size, 3.73's?
1701 @ 50, 2211 @ 65. With the converter locked.
You should be running a gray 15 tooth drive gear and a dark gray 44 tooth driven gear for your speedometer. That'll put you dead-nuts accurate with 245/50R16 tires.
If you have that and are still reading too many rpm, then your converter isn't locking like it should, or you're not getting 4th gear at all.
In third, with conv. locked, 65 mph is 3176 rpm.
You should be running a gray 15 tooth drive gear and a dark gray 44 tooth driven gear for your speedometer. That'll put you dead-nuts accurate with 245/50R16 tires.
If you have that and are still reading too many rpm, then your converter isn't locking like it should, or you're not getting 4th gear at all.
In third, with conv. locked, 65 mph is 3176 rpm.
04-13-2009 | 02:46 PM
#5
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iTrader: (2)
Joined: Jul 2007
Posts: 777
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From: Tampa/New Hampshire
Car: 91 camaro RS, 87 T/A
Engine: 350 TBI, 305 TPI
Transmission: 700r4
Axle/Gears: 4th Gen 3.42/BW 3.45
Re: Cruising RPMs with stock 700R4, stock tire size, 3.73's?
1701 @ 50, 2211 @ 65. With the converter locked.
You should be running a gray 15 tooth drive gear and a dark gray 44 tooth driven gear for your speedometer. That'll put you dead-nuts accurate with 245/50R16 tires.
If you have that and are still reading too many rpm, then your converter isn't locking like it should, or you're not getting 4th gear at all.
In third, with conv. locked, 65 mph is 3176 rpm.
You should be running a gray 15 tooth drive gear and a dark gray 44 tooth driven gear for your speedometer. That'll put you dead-nuts accurate with 245/50R16 tires.
If you have that and are still reading too many rpm, then your converter isn't locking like it should, or you're not getting 4th gear at all.
In third, with conv. locked, 65 mph is 3176 rpm.
I have always wondered this, but always thought my tach was off never got around to getting the drive/driven gears changed out. I have 3.42 gears and my cruising on Highway at around 70 is 3k. I still have the drive/driven gears for the stock 2.77 gears. Reading this thread makes me thing something is wrong with my tranny.
04-13-2009 | 06:28 PM
#6
Thread Starter
Senior Member
iTrader: (2)
Joined: Oct 2001
Posts: 646
Likes: 1
From: Sedalia, MO
Car: 1991 Z28 vert, 1988 GTA
Engine: 305 TPI, 305 Carb-finally runs!
Transmission: TH-700R4/BW WC T-5
Axle/Gears: 3.73 posi 4th gen 10-bolt/BW 9 bolt
Re: Cruising RPMs with stock 700R4, stock tire size, 3.73's?
thatnks for the advice everyone, tomorrow i'm gonna try and drive it around since it's kinda messy out right now. i'll report back with what i find, i've been reading up on it in the factory service manual.
04-13-2009 | 11:18 PM
#7
Junior Member
Joined: Apr 2009
Posts: 4
Likes: 0
From: germantown maryland
Car: 87 trans am
Engine: LB9 305 TPI
Transmission: 700R4
Axle/Gears: 2.73
Re: Cruising RPMs with stock 700R4, stock tire size, 3.73's?
i have a 87 trans am with the LB9 700R4 and 2.73 it dose about 2000 rpm at 75 in OD and about 3000rpm in drive at the same speed
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04-14-2009 | 12:58 AM
#8
Junior Member
Joined: Jul 2007
Posts: 31
Likes: 0
From: Montana
Car: 84 vette 85 vette
Engine: 350 crossfire, 350 TPI
Transmission: both 700R4
Axle/Gears: 84 vette 3.07, 85 vette 3.54
Re: Cruising RPMs with stock 700R4, stock tire size, 3.73's?
My 85 vette has auto 700r4 with 2.73 and at 60 mph it is about 1800rpm, what would it run with 3.73? The 2.73 gears arn't cutting it.
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