Automatic Transmissions for Fiero GTs (Page 2/2) armos MAR 03, 03:53 AM I've had 3 cars with the THM125C (2 Fieros and 1 Grand Am), and relatives have had 3 more (all 2.2L Cavaliers). Out of all 6 of those cars, the only one that had a transmission failure was a Cavalier that had been the first car for 4 consecutive teenagers over it's entire life. It died at only 120K - but 4 teenage owners. This was also the lightest of all the cars (a very low optioned 2 door Cavalier) with a 2.2L producing less torque than the 2.5L Duke or the 60V6. I'm going to dismiss that failure as probable abuse or neglect. Unlike some automatics, the THM125C has a dip stick, so if the owner is attentive enough to check it, it may tend to be better maintained than those that don't have one. My current 86GT has the automatic 3.33, it's up to 230K miles now and still works perfectly. This is the only one of those 6 cars that was a V6, the others were all 4cyls. But as I understand it, the V6 transmissions are built up a little more from factory to handle the extra torque, and so I don't think their track record is any different in the V6 application. Many people never change the fluid and filter in an auto trans. If you do buy an auto Fiero, it should probably be done. My car came with the lockup TCC connector unplugged, and when I plugged it in, there was a shudder. That cleared up after I did a couple fluid changes. The big con for the THM125C is that it doesn't get good highway mileage because it doesn't have overdrive. If you cruise at 75-80 it will cost you. It turns about 3500rpm@75mph with stock wheels and gearing. In California I was getting 22-24mpg depending how I drove. I was in the rural foothills so most of my miles were cruising (lots of elevation changes though). I would guess I was probably hitting 25mpg when strictly on a highway at a conservative speed (65 or less), but of course these cars don't have a dash gauge to tell me that, all I know is the final mileage per tank. Now that I'm in Florida I've been getting like 19-20mpg but I blame it on my short trips, and the increased desire to punch it either from restless boredom or merging into suburban traffic. Something might also be falling out of tune. Given the age of these cars, a heavy weighting should be placed on the condition of the car, most especially whether the frame is rotting (look under the trunk carpet). The best car you find might not be the one that has the options you want. But as far as reliability concerns, I don't think the 3spd auto has any. It's a solid transmission - just lacks overdrive. 82-T/A [At Work] MAR 03, 09:17 AM quote Originally posted by armos: In California I was getting 22-24mpg depending how I drove. I was in the rural foothills so most of my miles were cruising (lots of elevation changes though). I would guess I was probably hitting 25mpg when strictly on a highway at a conservative speed (65 or less), but of course these cars don't have a dash gauge to tell me that, all I know is the final mileage per tank. Now that I'm in Florida I've been getting like 19-20mpg but I blame it on my short trips, and the increased desire to punch it either from restless boredom or merging into suburban traffic. Something might also be falling out of tune. This has me thinking too... I have a 2002 Crown Victoria LX-P74. It's a cream-puff as they say. I basically got it in 2004 from my grandfather (when he passed away), who bought it new. I've done a number of things to it, but it has a 2.73:1 final drive gear ratio, which I've left. The transmission... I can't remember, is a 4-Speed. When I lived in Florida back just prior to ~2011, I was getting ~28mpg... which is quite good for a 5,000 pound car with a 4.6L V8 engine. Absolutely nothing has changed on the car since 2011, except that I've changed the tires, and changed out the fluids. The car still only has like 50k miles on it as it sits, and sometimes I go 6 months without driving it... but it now only gets around ~25 miles to the gallon on the highway. There's been some more obvious changes in the fuel that we now use today, versus what we used 10 years ago... but I'm wondering if that seems to be more of what's going on? I'm unable to get more than 25 miles to the gallon. armos MAR 03, 06:17 PM quote Originally posted by 82-T/A [At Work]: This has me thinking too... I have a 2002 Crown Victoria LX-P74. It's a cream-puff as they say. I basically got it in 2004 from my grandfather (when he passed away), who bought it new. I've done a number of things to it, but it has a 2.73:1 final drive gear ratio, which I've left. The transmission... I can't remember, is a 4-Speed. When I lived in Florida back just prior to ~2011, I was getting ~28mpg... which is quite good for a 5,000 pound car with a 4.6L V8 engine. Absolutely nothing has changed on the car since 2011, except that I've changed the tires, and changed out the fluids. The car still only has like 50k miles on it as it sits, and sometimes I go 6 months without driving it... but it now only gets around ~25 miles to the gallon on the highway. There's been some more obvious changes in the fuel that we now use today, versus what we used 10 years ago... but I'm wondering if that seems to be more of what's going on? I'm unable to get more than 25 miles to the gallon. If it sits a long time that might be having a negative effect, especially on the fuel system. You could end up with a misbehaving injector, for example. My nephew had a Town Car for a while. Those are such roomy and comfortable cars, they put other modern cars to shame. Unfortunately his went downhill for various reasons (not the car's fault). I noticed the mileage drop as soon as I moved. California does have it's super-special unique formula for whatever reason, so I'm sure the gas I'm using now is different in some way. I'd be surprised if CA gas has a higher energy content, but even if it does, for paying half the price in FL I'll take that trade. I immediately noticed I'm making more power here, which I assume is just because of lower elevation. I did mess with the tune on my Fiero years ago, so maybe it doesn't work as well at this elevation, but I plugged a laptop into it once since moving here and didn't notice anything looking different than it did in CA. I want to convert my car to a 7730 ECM. I have most of the parts, just need to get going on the project. It might get better mileage with that. There's a station nearby that sells ethanol-free. Unfortunately it's 93 octane premium also - so it costs too much extra for me to bother trying it. I wish somebody sold 87 octane ethanol free, I'd be more interested in running that. 82-T/A [At Work] MAR 03, 08:07 PM quote Originally posted by armos: If it sits a long time that might be having a negative effect, especially on the fuel system. You could end up with a misbehaving injector, for example. My nephew had a Town Car for a while. Those are such roomy and comfortable cars, they put other modern cars to shame. Unfortunately his went downhill for various reasons (not the car's fault). I noticed the mileage drop as soon as I moved. California does have it's super-special unique formula for whatever reason, so I'm sure the gas I'm using now is different in some way. I'd be surprised if CA gas has a higher energy content, but even if it does, for paying half the price in FL I'll take that trade. I immediately noticed I'm making more power here, which I assume is just because of lower elevation. I did mess with the tune on my Fiero years ago, so maybe it doesn't work as well at this elevation, but I plugged a laptop into it once since moving here and didn't notice anything looking different than it did in CA. I want to convert my car to a 7730 ECM. I have most of the parts, just need to get going on the project. It might get better mileage with that. There's a station nearby that sells ethanol-free. Unfortunately it's 93 octane premium also - so it costs too much extra for me to bother trying it. I wish somebody sold 87 octane ethanol free, I'd be more interested in running that. Yeah, I can't remember if I mentioned it above, but I ended up having to replace the fuel pump. But that was after it sat for 3 years... literally having never been run. I put in some fresh gas, put in a new battery, and it wouldn't turn over. I changed out the fuel pump (I don't remember why I thought that was the problem), and it fired right up. At the time, there was also a relay inside the cabin that was sticking, as I heard it clicking on and off. But I drove it for a couple of days, and all the problems went away. Obviously, I had to get new tires too, hahah. I drove it maybe once every couple of months for three years... basically put like 500 miles on it that year. And then took it from Fort Lauderdale to San Antonio... where it basically sat again for 4 years. I started it only a few times a year. I love the car, I really do... it's awesome, but it's so huge that when I'm getting around, the last thing I want to do is drive a gigantic battleship. To be completely honest, if it wasn't for the fact that it was my grandfathers... I would have sold it already. But I can't bring myself to do it. The 7730 is a pretty sweet ECM, lots of features that you can enable, like a knock sensor, better MAP, and other features. The communication baud rate of the system is significantly faster too than the original Fiero ECM... like, significantly more powerful. You can also run an open-loop oxygen sensor too, which is nice. They do actually sell 87 Octane, ethanol free, here in Florida. It's at select Race Track gas stations. Obviously not all the pumps have it, but there's usually at least one pump. My parents live in The Villages, and every time I go there, I fill up with ethanol free gas. armos MAR 04, 01:05 AM quote Originally posted by 82-T/A [At Work]: They do actually sell 87 Octane, ethanol free, here in Florida. It's at select Race Track gas stations. Obviously not all the pumps have it, but there's usually at least one pump. My parents live in The Villages, and every time I go there, I fill up with ethanol free gas. I'll have to keep an eye out for that. I haven't normally been going to Racetrack stations, but there is one nearby I should check. At least I think it's Racetrack - I can never keep Speedway and Racetrack separate in my mind. cvxjet MAR 04, 01:53 AM On my 1985 SE V6 (W/ Manual trans) I was getting 20 around town and 28 on the highway. At the ripe old age of 15 (Car age), I swapped in a getrag- and a 3.4 F-body block...I then was getting 19/30. By the way, my 1999 Firebird Formula (Automatic) got 30.4 MPG on a trip from CA to Oklahoma City...I was doing 70-75 the whole way and had the AC running (Except early morning). The car only had 2000 miles on it when I started that trip. When I told a co-worker at the CG air station, he became very angry- his Volvo wagon could only get 23 MPG highway driving. I wish there was a light 4 speed automatic for the Fiero- but all the 4 speed autos weigh a lot more...