proper setup

T

t/anewbiemoreinfo

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Hi. i am new to the forum and am looking for answers. Also new to the muscle car world. I have just purchased a 1981 trans am with a dart 502 block bored and stroked to 555 and don't have much in the way of specs. Am looking to be able to drive this car occasionally in town and highway. I do know it is equipped with 6000 rpm tach, a t3 speed manual vb auto transmission, 3700 stall converter, 3.08:1 gears and 235/55/17 tires. is it possible to tell from this info if it is streetable or if I would have to make some changes. Car will not be driven much so looking for lowest cost option so I don't destroy converter or transmission. Any help out there would be greatly appreciated. Thank you.
 
it would be very helpful to know the cam specs and compression ratio, obviously with a 555 displacement you should make impressive torque/ hp, but with a 3700 rpm stall converter its likely your engine assembler selected a fairly radical cam design,
and generally a 3.08 rear gear would be a mis-match to a 3700 rpm stall converter
I think youll have to just test drive, see what the engine power curve characteristic show and only then think of any required mods if any!


 
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Grumpy said:
it would be very helpful to know the cam specs and compression ratio, obviously with a 555 displacement you should make impressive torque/ hp, but with a 3700 rpm stall converter its likely your engine assembler selected a fairly radical cam design,
and generally a 3.08 rear gear would be a mis-match to a 3700 rpm stall converter
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Grumpy said:
( I hope the engine, components are the displacement you quoted, as thats obviously an impressive & expensive basic engine if its as quoted)
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Grumpy said:
I think youll have to just test drive, see what the engine power curve characteristic show and only then think of any required mods if any!
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I am trying to locate previous owner because I purchased this vehicle from a dealer who told me that is all the info they had. If I can get any documentation I will let you know. Thanks Grumpy.
 
Wow, being new to muscle cars, you jumped right in with both feet! Nice! :like: And welcome to the site!
Just looking at what you wrote, I agree with Grumpy that the converter and rear gears are mismatched. The 3700 stall converter has borderline too much stall for a street car. Not sure you would be happy with the engine noise and poor gas mileage. Being that you have a pretty stout BBC, a 2500-2800 RPM stall converter with a 3:55 - 3:73 rear end gear would be a more logical and streetable choice.

Any combo including yours is ”streetable”; it really depends what you want from the car and how much you are willing to put up with. If you decide to keep the 3700 converter, make sure you have a very good transmission cooler and a transmission temperature gauge as that converter will be dumping a lot of heat into your transmission fluid!

Just my $0.02!
Kenny Bee
 
First, welcome to the forum from Oklahoma !

That rear gear ratio of 3.08 is suspect, since it's coming from a sales person. It's too easy to verify that rear end gear ratio, so that would be one of the first things I would do.

First you will need to determine if it's an open diff or a limited slip diff. Jack up the rear end, put the trans in neutral and spin one of the tires. If they both tires spin in the same direction, then it's a limited slip rear diff, if the spin in opposite directions then it's an open diff.

Now watch the appropriate video below and calculate your rear end gear ratio.

Open Differential

Limited Slip Differential
,
 
Congratulations on your purchase and welcome to the passion.

I didn't intend for this to be my first post without a proper introduction, but I have been right where you are and I get it.

I would strongly recommend starting fresh and changing all the fluids. I would pull the differential cover to drain it and clean it out. That way you KNOW exactly what you have to start with.

While you have the cover off:
1. Note how many bolts hold it on, 10 or 12?
2. The gear ratio will be stamped into the ring gear.
3. You will be able to identify what type of differential unit you have. If not, posting pictures here will definitely tap into the wealth of knowledge.
4. Once you know what differential type you have, you can select the correct oil and friction modifier you need to run.
5. You will also be able to inspect everything as you go.

Once you know the gear ratio and tire diameter, you can figure out the stall of the converter and its suitability to your application. Heat is a real killer of automatic transmissions. As mentioned above, high-stall converters build a tremendous amount of heat.

That generation TA came with either a 10 or 12 bolt axle. Something would have to be terribly wrong for your 555 to not be producing a lot of torque. However, you don't have a lot of tire. It would be nice if you had a 12-bolt axle for when you step up your traction and actually hook, otherwise that 555 will help you upgrade your axle sooner than later.

That's not to say that you can't enjoy your car without upgrades, it all depends on your driving style and intended usage. If you aren't hammering on it, you won't break parts, but where's the fun if you can't drive it as it was intended?

When you get to the transmission, you probably have a TH400 (Turbo-Hydromatic), but it would be nice to know for sure. If your trans pan doesn't have a drain plug, now is a great opportunity to add one. Maybe even consider a finned aluminium pan, that would help dissipate heat. Just don't go for a deep pan that hangs down and drags on everything.

While you are under your car, look at EVERYTHING. It's good to KNOW what you have and develop a more intimate relationship with your car.

Cheers,

Joe

P.S. If necessary, you can have your torque converter repitched for your application.
 
Flusher said:
I would strongly recommend starting fresh and changing all the fluids. I would pull the differential cover to drain it and clean it out. That way you KNOW exactly what you have to start with.
Click to expand...
I like it, taking the ultimate step by changing the fluid and actually getting the number of teeth on the ring and pinion to determine the gear ratio!

Welcome to the forum Flusher !
 
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