Let me start by saying I am no expert when it comes to building cars this is my 1st project. I appreciate any advice or opinions that anyone has to give. Thank you in advance. I currently have a 84 cutlass with a 454 engine. Th350 with a 9in rear end with 3.89 gears. Originally I was told this would be a good gear for cruising on the highway as that is kinda what I want to do mostly. I just really want to be able to enjoy that car and spin the tires. Car seems to only have 2 gears and I was told that I need smaller gears to be able to cruise on the highway. Car is fine around 55 60 mph but then after that seems as tho it just revs and needs another gear. So I don't know if it is the transmission or if 3.42 or 3.55 or even 3.73 gears will work. Again I am new and learning every day and I appreciate any assistance or guidance. Thanks.
Need help with gears? 3.89
- Thread starter Scubby13
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You might be happier with 3.55s if you go any higher geared than that you might find it sluggish off idle
If your pocket book will allow it install an overdrive transmission and keep the 3.89s
I’ve had 373s with a 700r4 and it was perfect for me
If your pocket book will allow it install an overdrive transmission and keep the 3.89s
I’ve had 373s with a 700r4 and it was perfect for me
Your reference to it feeling like it only has 2 gears is somewhat disconcerting. Do you believe the transmission is slipping in 3rd gear? Does the car have a tachometer? Asking because a tachometer makes gear determination/recommendation much easier, and will identify if you have a transmission issue.
What size tires are you running?
What size tires are you running?
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The gears are fine for the highway.
Assuming your TH350 is fine, I'd look for an online gear calculator and just play with the numbers. For a highway cruiser something in the 3:00 - 3.25 range will probably work. Your 454 should still light those up at a light just fine. I'd probably stay away from anything deeper than that unless you are planning an overdrive swap to go with it. No fun being tach'd out and not even keeping up with traffic.
There's a loose rule that 10:1 compound 1st is a sweet spot. You'll also need to consider converter stall speed and cam specs too. It's a balancing act and you may need to make a compromise somewhere if it all doesn't match.
There's a loose rule that 10:1 compound 1st is a sweet spot. You'll also need to consider converter stall speed and cam specs too. It's a balancing act and you may need to make a compromise somewhere if it all doesn't match.
If you need a 3.89 gear to launch your 454, something is very wrong, like a ridiculous cam. I assume you also have an aftermarket converter? That could be slipping more as well, increasing highway rpm even more. Guessing from the pics you probably have 255/60R15 tires on the back, you will be around 3200 or 3300 rpm at 60 mph. Go to 70 mph, 3500+ rpm. Do you have a tach?
If the trans is fine, it probably sounds worse than it really is. Compared to todays cars that cruise at 2-2200, a car at 3500 sounds like its screaming. 3.89 is a little much for a highway cruiser in today's terms. Back when 55 was the speed limit and 60 was flying, a 4.10 gear was accepted as normal. I ran 4.10's with a 275/60 tire in my Nova at 3300 to go somewhere just over 60. If I had to choose today for a non overdrive car, I would stay at 3.42 or less. I have 3.55's in my Chevelle and if I ever get around to building the 10 bolt for the Malibu it will be 3.42.
I had 308s in a 67 camaro , I could do 140 mph at redline , but I needed all 435 horses of the 383 to make it launch against cars with less motor
Also had trouble driving at parade speed , 21 mph was about as slow as you could drive it without brake clutch gas repeat
Sucked *ss actually swapped to 373s with an m20 and was wayyy more better on the street
Iroc z with 373 behind a 700 r4 makes your car move ! Lol
Also had trouble driving at parade speed , 21 mph was about as slow as you could drive it without brake clutch gas repeat
Sucked *ss actually swapped to 373s with an m20 and was wayyy more better on the street
Iroc z with 373 behind a 700 r4 makes your car move ! Lol
If you do have a radical cam. I would switch it for something milder then you could put in something like a 308 gear that was mentioned. Still have plenty of low end torque and be more comfortable to drive on the highway.
If you could spring for a overdrive trans that would really give you what it shoulds like you are wanting.
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