Thirdgen F-body FAQ


General Questions:

What options did my car come with?
-The best way to tell what options your car came with from the factory is to find the SPID Label (Service Parts IDentification) also known as the RPO codes.  It will list "codes" for all options available that were installed from the factory.  The most common place for this sticker was in the center console.  There have been reports of them also being stuck in the rear storage compartment, but mostly in the center console.  Each code will indicate a specific option, or group of options.  For example, N10 was the code for dual converters, and G80 was the code for limited slip, but code G92 was a performance package that included both options (the options will still be listed separately, in conjunction with the package code).  GM produced books that list all of the option codes, as well as other websites.  If you cannot find your SPID label, you may be able to go to the nearest GM Dealer and have them look up your VIN number and they may be able to retrieve your codes.

How many (insert your car here) were made?
-Thats not an easy question to answer.  GM didn't keep track of how many cars were made with certain options.  Major combinations like how many T-Top cars, or how many Z28s or how many 350's were recorded, but if your looking for how many Purple RS's with Gray Leather, LO3 engine, M30 Transmission,  GU5 axle were made, forget about it.  Production numbers didn't get that detailed.  To see a list of some production numbers, click HERE.

Can I run dual exhaust on my car?
-Technically, yes you can.  Is it easy or necessary?  Thats in the eye of the beholder.  Exhaust can get pretty cramped under a thirdgen as it is, let alone a pair of exhaust pipes.  Not to mention, "studies" have been done, and supposedly, dual exhaust isn't needed or even provide benefit until 450+ HP.  A decent mandrel bent 3" single exhaust will support what most people put under the hood, so unless you have a real radical setup, true dual exhaust is not needed.  But if your really set on being like your buddies Mustang, it can, and has been done before.   Oval tubing has been developed that will allow two pipes run side by side without taking up as much space.  Ideally, you want to run the pipes over the axles.  I have seen setups that had straight pipes run under the rear axle which is not desirable.

What will my car run at the track?
-A lot of that has to do with year, engine, tranny, equipped options, driver, and of course, what modifications have been done, if any.  Its really hard to say what a given car will run due to the amount of variables involved.  I have seen stock 350's run 15's in the quarter mile, and I have seen modded 305's run 13's.  Its all about engine output, driver ability, vehicle weight, etc...  To see what a few stock thirdgens have been reported to run based on magazine publishers testing, click HERE.

Why does my car appear to run hot?
-Before you start chasing a problem, make sure it really is running hot.  The stock gauges in these cars leave much to be desired.  Its very possible that the gauge is inaccurate, giving you false readings.  If a scantool is available to you, you may want to monitor the scantool's reading of coolant temp and compare it to the gauge.  Also be aware that the ECM, with stock calibration, will not turn the fan on until 225°.  If you have dual fans, the secondary fan will not come on until over 230°!  So the car may appear to be running hot, but its actually performing as designed.  However, if you are in doubt, it would behoove you to get it checked out.  Its better to have it checked and there be nothing wrong, then to forget about it and really have a problem!

How can I make my fans come on sooner?
-There are really two ways that have been accepted into the Third Generation community.  The first and most reliable is to have the EPROM (computer chip) reprogrammed with lower fan temp settings.  Aftermarket chip makers sell chips with lower settings, which usually include a lower thermostat.  Anybody who does chip burning on there own can also perform this function.  This is most desirable because once the chip is burned, its idiot proof.  There is no user input required.  Once the ECM sees the coolant temp get to the specified value, it will turn the fans on.

The second method is to install a manual fan switch.  This usually involves installing a toggle switch inline to the relay signal wire and ground.  This is effective, however, you must turn the fan on and off manually every time.  Also, if you have completely disabled ECM control over the relay, forgetting to trip the toggle switch could prove disastrous.  Most people that use a toggle switch tap into the ECM control wire, so that the ECM can provide a backup, incase the switch fails or the user forgets to turn it on.


What engines were available, what did my car come with?
-There were several engine options available.  This included a four cylinder, various V6 combinations and a plethora of V8s.  There are two ways to know what the stock engine/induction combination was.  The easiest is to look at the VIN, or you could also find your sticker containing RPO codes.  The engine code in the VIN is the eight character, and usually the engine RPO code will start with the letter "L".  To see what VIN character or RPO's were used sorted by year, click HERE.

How can I make my car faster?
-This is a loaded question.  First you have to decide how far you want to go and how much you want to spend. When it comes to speed, the sky is the limit, but it all comes with a price.  You can do simple "bolt-on" mods like a "high-flow" air filter, lower thermostat, etc... for not a lot of money, but you will also get minimal gains. You can increase your budget and pick up items like headers, cat-back exhaust and perhaps a higher flowing intake manifold.  For even more gains (and of course money) you can go for a larger camshaft, high flow cylinder heads, etc...  For those wanting lots of speed, you could get a Nitrous kit, or a supercharger or turbo.  Manufacturers make a variety of performance parts for almost any engine.  It doesn't have to be limited to just the engine either.  You could try different rear axle gears, better tires, suspension mods, etc...

Can I swap my V6 for a V8?
-Absolutely!  Its a big undertaking, but a very common swap. Many things will have to be addressed, like induction system, wiring, transmission, exhaust, etc...  If you can find a V8 car that has been totaled for a donor, thats a good way to have most of the parts you need handy, not to mention you can see where everything needs to go. Obviously, the V6 intake/fuel system won't work on a V8, so you can swap in the TPI assembly, TBI or carburetor, whichever you prefer.  You will need the proper wiring to go with the induction system.  V6 F-bodies had a 60° bellhousing pattern, which means that the V8 will not bolt to it.  Therefore, you will need to find a tranny that shares the same 90° bellhousing, such as another V8 or the 4.3L V6.  The stock exhaust from the catalytic converter and back will work, but you will need the V8 manifolds or upgrade to headers.  There are many other things to consider, to much to list here, but it can be done!

What type of rockers arms do I need?
-You'll have to look under your  valvecovers to find out for sure, but most use self-aligning rocker arms.  There needs to be some method of keeping the rocker centered on the tip of the valve stem.  Two methods are used.  One is to use guideplates and non, self-aligning rockers, which will keep the pushrod from moving, which in turn keeps the rocker arm steady.  The other method is to not use guideplates and use a self-aligning rocker to keep it centered.  If the cylinder head does not have guideplates, then you must use self-aligning rockers.  You can tell a self-aligning rocker as it will have "guides" or walls on both sides of where the valvestem contacts the rocker.

Do I have an engine oil cooler?
-If you have an oil cooler from the factory, you will have RPO code "KC4".  Another way to tell is by looking right above your oil filter.  If there is a piece sandwiched between the filter and the block with coolant lines plumbed to it, you have a cooler.  Coolant that had passed through the radiator after being cooled is routed through the oil filter adapter to cool the oil.

What is setting "Minimum Air and TPS?"
Minimum air is the adjustment of how many RPM's the car will idle at when the Idle Air Controller is fully seated.  This is important because if its to low, the car will stall, usually when coming to a stop or after being revved, and if its to high, the idle will be too high and the computer will not have proper control over the idle.  Setting the TPS, if its adjustable, is also important because there is a voltage range that the computer needs to see at idle and if the minimum air was adjusted (throttle plates opened or closed) then the TPS voltage will be incorrect.  You must set the minimum air first, then the TPS.  To find out how to perform these, check out the tech articles.

What do I do when my "Check Engine Light" comes on?
-First, don't panic, the light came on because some sort of failure has been detected, but it shouldn't mean your stranded.  Second, all you need to do to find out why it came on (or at least a general idea) is to find yourself a paper clip, and read this article:  Checking DTCs

What is a MAT/IAT sensor?
-These are the same sensors, just different names.  MAT stands for Manifold Air Temperature and IAT stands for Intake Air Temperature.  They measure the temperature of the Air in the Intake Manifold.  This is an input to the ECM for determining proper calculations for air/fuel mixture.

Can I relocate my MAT sensor?
-This is a common modification to "richen" up the fuel mixture. Normally, the MAT sensor screws into the bottom of the TPI plenum, which can get very hot.  Its not uncommon, when viewed with a scantool, to see MAT temperatures over 100° even when the outside air temp is much lower.  By relocating the sensor to a much cooler place, it will register the incoming air as a much lower temp (and much denser) and cause the computer to add more fuel.  With either an adjustable fuel pressure regulator or the ability to burn your own computer chips, relocating the sensor isn't required.

What size throttle body should I use?
-This is an often debated question.  The stock size is 48mm, used on both the 305 and the 350.  General rule of thumb is for anything less then a 383, use a 52mm.  383 and above, use the 58mm throttle body.  Using to large of a throttle body is just like using to big of a carburetor.  If the engine cannot support the added airflow, then it will not give you any gains, and can actually hurt performance and cause drivability to suffer.

What are the coolant lines running in front of my engine?
-If you have these, you have an engine oil cooler.  They are coolant lines that run in front of the engine, and back to the oil filter assembly where the coolant cools the oil as it goes through the oil filter adapter.

Do I really need a 4-bolt block?
-General rule of thumb is unless you realisticly plan on running over 500HP or plan on turning lots of RPMs, a two bolt block will suffice just fine.  Most street combinations are well under 500 HP, and never go past 6,000 RPMs, so most street setups will be just fine with a two bolt.  It doesn't hurt to run a four-bolt, just cost a little extra.

Can I use the Corvette Aluminum L98 heads on my car?
-Absolutely!  These are great  heads to boost perforamnce.  They are aluminum and feature 58cc combustion chambers which will boost up the compression.  The only drawback to these heads is the lack of EGR provisions.  If you want to use these heads and remain emission legal, you will need to have the EGR externally plumbed.  If your using TPI, you can simply use a Corvette TPI base and plumb exhaust into the port provided.  Vortec TPI base has the same provisions and the adapter pipe can be purchased from the same supplier as the base.

Transmission/Rear Axle

Can I swap out my auto tranny for a manual?
-Yes you can!  There was a very detailed article written about how to perfrom an auto to T-5/T-56 swap.  You can read it HERE.

Did my car come with an aluminum driveshaft?
-One way to tell is to get under the car and look.  The aluminum will have a gray/silver color to it and a magnent will not stick to it.  The steel driveshaft will probably be rusty and a magnent will stick to it.  Another way to tell is look for RPO code "JG1".  This indicates that the car came from the factory with the aluminum driveshaft.


Why won't my car shift into OD at Wide Open Throttle?
-Most 700R4s will not let you hold fourth gear at Wide Open Throttle (WOT).  Some of the high performance models allowed you to do this, as well as the Police Car packages like that found in the Caprices upfitted for police use.  There are two ways to allow your car to hold 4th at WOT.  You can either install the "Police Package Correction kit" which is available from your GM Dealer, or you can either block the Detent passage in your Throttle valve plunger bushing, or just replace the plunger bushing with an aftermarket one from companies like Superior.  The GM Valve kit is P/N 8671953.  It replaces the 3-4 shift valvetrain.  Or  you can use the Throttle Valve bushing from Superior, or you can modify your existing bushing, but it requires alot of work, you may just want to buy the aftermarket one!

What gears do I have?
-There are several ways to find out.  Assuming you have a 26" tire, you can travel at 70 MPH with your tranny in the 1:1  ratio (3rd gear for 700R4s, 4th gear for T-5 manuals).  When you reach 70MPH, assuming your tachometer is correct, look at your RPMs.  An RPM reading of 2,730 +/- would indicate 2.73 gears.  3,230 RPMs +/- would indicate 3.23s;  3,420 = 3.42;  3,730 = 3.73, etc...

Assuming your rear end/ gears are stock, you could either look at your RPO codes, or look on the axle itself for the Axle Code.  Click HERE for more info on Axle/RPO codes.

Finally, and the mos accurate way to know for sure what your gear ratio is, is to remove the ring and pinion and count the teeth.  Take the number of ring gear teeth and divide by the number of pinion teeth.  Usually you can see these numbers stamped on the head of the pinion.

How do I install a Posi?
-You can either replace the whole carrier w/ a limited slip unit like the Eaton or Auburn, or get an OEM unit like the Torsen take-outs for sale on the SLP website.  This will require removal of the ring gear, being transfered over to the new carrier and resetting up the rear end.  Since carrier sizes can differ due to manufacturing tolerances, you MUST setup the rearend as though you were installing a new ring and pinion.  You'll want to make a backlash measurement and tooth pattern contact BEFORE dissasembly, and put it back together to acheive the same readings.  You also must get proper side bearing pre-load.  To find out more about setting up rearends, click HERE.

What tranny do I have?
-First you need to determine if its a manual or automatic transmission.  If its an auto, there were two available.  The 200C and the 700R-4.  Only early thirdgens had the 200C, and it was a three-speed, so if you have a 3 speed auto, it was a 200C (not to be confused w/ a 2004-R) and if it was a 4-speed auto, it was a 700R-4/4L60 (not to be confused w/ a 4L60-E).  There were also a 4-speed manual and a 5-speed manual.  Only the early thirdgens had the 4-speed manual.

How much fluid does my Automatic Transmisson hold?
-Completely empty, the 700R-4/4L60 holds 11 quarts.  After just a filter change, it holds 4-5 quarts.

Why does my  tranny shift funny?
-There are numerous problems that can cause the transmission to not act properly.  It could be something simple like the TV Cable not being adjusted properly, or could even be something more serious than a shift problem, but actually burnt clutches or broken parts.  If it shifts late and hard or soft and early, try adjusting the TV Cable first.  Not sure how?  Click HERE. If its still shifting late and hard and the adjustment didn't help,  you have have the Throttle Valve itself stuck in the valvebody.  This is a common problem w/ the 700R-4.  As it sits in the car, there isn't much you can do about it to fix it, other than  yank on the cable a few times or ride it out hoping it frees up.  The only way to fix it for good is to install a TransGo Reprogramming kit.  In the kit, it has a patented "self cleaning" Throttle valve w/ booster springs.   If its not shifting at all, you might have a stuck governer.  You can try removing it and seeing if the valve in the center moves freely.   It may not even be a shift problem at all.  If the vehicle slips on the 2-3 shift, or has a "flare", it may not be the "shift" but the clutches slipping.  This would require an overhaul.

Whats the difference in T-5 transmissions?
-There were two available:  The Borg Warner T-5 and the World Class T-5.  GM started using the "non World Class" T-5 tranny in the thirdgens starting in 1983.  Starting in 1998, the World Class T-5 made its appearance in the thirdgens.  The WC T-5 was much stronger and a more desireable tranny.