TH350 Question
Thread Starter
Heel & Toe
Joined: Sep 2005
Posts: 21
Likes: 0
From: Rescue CA
TH350 Question
Just purchased a 79 Corvette that has the TH350 transmission. When I am driving at 55MPH my TAC shows around 3000RPM and at 70MPH your pushing close to 5000RPM, you can really here the engine winding up. I read in a after market manual that the Corvette TH350 is a modified transmission, but It didn't stat what was modfied. Does anyone know if the Corvette TH350 is geared diffrent?
It just seems like I'm missing a gear to go into.
It just seems like I'm missing a gear to go into.
Pro
Joined: Nov 2004
Posts: 575
Likes: 0
From: Nice Lake Ontario
Well can you feel it shift 1-2, & 2-3 when you start from a dead stop??
Either that or you got a wicked set of gears 4.56s?
My old 74 would run to about 100mph in 2nd with whatever gears it came with? probably 2.73s
Either that or you got a wicked set of gears 4.56s?
My old 74 would run to about 100mph in 2nd with whatever gears it came with? probably 2.73s
Drifting
Joined: Mar 2005
Posts: 1,806
Likes: 3
From: Burlington WI
I have a 78
with 3.08 gears. At 70 I am turning about 3200.
If it is turning 5000 at 70 it mus be screaming pretty good.
Either someone put some really low gears in that car or your tach is way off.
If it is turning 5000 at 70 it mus be screaming pretty good.
Either someone put some really low gears in that car or your tach is way off.
Le Mans Master
Joined: Jun 2004
Posts: 9,289
Likes: 16
From: Skippack PA
St Jude Donor '13
Originally Posted by fl_rider
with 3.08 gears. At 70 I am turning about 3200.
If it is turning 5000 at 70 it mus be screaming pretty good.
Either someone put some really low gears in that car or your tach is way off.
If it is turning 5000 at 70 it mus be screaming pretty good.
Either someone put some really low gears in that car or your tach is way off.
I have the TH350 on my 80 L82 with stock gears and at 75mph I'm right around 3500.
Le Mans Master
Joined: Apr 2000
Posts: 5,981
Likes: 0
From: Houston,Tx. USA
Originally Posted by fl_rider
with 3.08 gears. At 70 I am turning about 3200.
If it is turning 5000 at 70 it mus be screaming pretty good.
Either someone put some really low gears in that car or your tach is way off.
If it is turning 5000 at 70 it mus be screaming pretty good.
Either someone put some really low gears in that car or your tach is way off.
Thread Starter
Heel & Toe
Joined: Sep 2005
Posts: 21
Likes: 0
From: Rescue CA
Not sure what gearing I have in the rear end. The Chilton manual talks about a code on the axel carrier that defines what gears you have in the rear end and I have not been able to find it so far.
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Burning Brakes
Joined: Jun 2005
Posts: 764
Likes: 2
From: THE OLDER I GET THE BETTER I WAS! NORTHERN ONTARIO
Originally Posted by rtee
Not sure what gearing I have in the rear end. The Chilton manual talks about a code on the axel carrier that defines what gears you have in the rear end and I have not been able to find it so far.
Thread Starter
Heel & Toe
Joined: Sep 2005
Posts: 21
Likes: 0
From: Rescue CA
Took a spin around the block and she shifts from 1 to 2 and 2 to 3 with no problems.
The Chilton manual shows for the 79 they came with a 3.36, 3.55 or 3.70. It looks like I might have the 3.70. I wasn’t able to find the code on the rear axle, but a work buddy told me how I could get some type of idea of what the rear axle ratio is.
By jacking up the rear end so the back wheels are off the ground, mark a line on the drive shaft and mark a line on one rear tire. By slowly spinning the tire watch the drive shaft line that you marked on the shaft. Every time the line you marked on the drive shaft goes by that’s one. You will want to only rotate the tire one time meaning if you mark a line at 12 O’clock then you spin the tire until you get back to 12 O’clock. So 3 ¾ spins on the shaft should be around a 3.70 ratio.
If anyone knows exactly where the code is located please let me I would like to know for sure what I have.
Thanks…
The Chilton manual shows for the 79 they came with a 3.36, 3.55 or 3.70. It looks like I might have the 3.70. I wasn’t able to find the code on the rear axle, but a work buddy told me how I could get some type of idea of what the rear axle ratio is.
By jacking up the rear end so the back wheels are off the ground, mark a line on the drive shaft and mark a line on one rear tire. By slowly spinning the tire watch the drive shaft line that you marked on the shaft. Every time the line you marked on the drive shaft goes by that’s one. You will want to only rotate the tire one time meaning if you mark a line at 12 O’clock then you spin the tire until you get back to 12 O’clock. So 3 ¾ spins on the shaft should be around a 3.70 ratio.
If anyone knows exactly where the code is located please let me I would like to know for sure what I have.
Thanks…
Advanced
Joined: Apr 2004
Posts: 74
Likes: 0
From: Iron Station N.C.
According to one of my books, the code is located on the bottom of the differential carrier housing by the cover.
Posi 3.36 CODE OM
Posi 3.55 OH
Posi 3.70 OJ
Plant Code:
Buffalo C
Chev Gear & Axle G
GM of Canada K
Warren W
Shift code:
1st Shift 1
Day Shift D
Night Shift N
Posi 3.36 CODE OM
Posi 3.55 OH
Posi 3.70 OJ
Plant Code:
Buffalo C
Chev Gear & Axle G
GM of Canada K
Warren W
Shift code:
1st Shift 1
Day Shift D
Night Shift N
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
Originally Posted by rtee
Just purchased a 79 Corvette that has the TH350 transmission. When I am driving at 55MPH my TAC shows around 3000RPM and at 70MPH your pushing close to 5000RPM, you can really here the engine winding up. I read in a after market manual that the Corvette TH350 is a modified transmission, but It didn't stat what was modfied. Does anyone know if the Corvette TH350 is geared diffrent?
It just seems like I'm missing a gear to go into.
It just seems like I'm missing a gear to go into.
Melting Slicks
Joined: Jul 2005
Posts: 2,545
Likes: 3
From: 406ci SB, AFR 180 Heads - 490 HP @5,600 RPM 529 lb-ft @ 4,100 RPM
Originally Posted by rtee
Just purchased a 79 Corvette that has the TH350 transmission. When I am driving at 55MPH my TAC shows around 3000RPM and at 70MPH your pushing close to 5000RPM, you can really here the engine winding up. I read in a after market manual that the Corvette TH350 is a modified transmission, but It didn't stat what was modfied. Does anyone know if the Corvette TH350 is geared diffrent?
It just seems like I'm missing a gear to go into.
It just seems like I'm missing a gear to go into.
