I purchased an SC 3800 swapped 85 Fiero earlier this year. I had it running good for a short while before it started having, what I assume to be, transmission problems. The previous owner claimed to have changed the fluid and put the proper amount back in, against my better judgment I didn't check for myself. When I started having problems I finally checked and found out I was running way low, so I put the proper amount in. The fluid was clean, but there was metallic sludge on the drain plug. However, that may just be regular wear. The issue is, sometimes, when in Drive, it won't go into 3rd, it will just stay in 2nd. At first I thought it was a linkage issue, because it seemed like I could find a spot, fiddling with the shifter, that would allow me to shift into 3rd just fine. With no issues, if I could find that spot, I wouldn't have problems. But it was really difficult to get it into that spot, there didn't seem to be a pattern, it just happened sometimes. I played around with the linkage some more, including using the shift plate to shift it into Drive manually, without using the shift lever in the cabin. Didn't fix it. After reading online I thought that maybe the solenoids were sticking. So I purchased a new set of those and have replaced them. I'm putting the transmission back together today and am going to work on getting the cradle back into the car. I'm very worried that this won't fix the issue, but I don't have the best grasp of how auto transmissions work. I'd like to take it to a shop but the best shop in my town claims they won't do it for less that $2K, they were also extremely rude and unhelpful.
I'm still going to put it back together because it'll either fix it or it won't, and I don't feel comfortable going any deeper into the transmission than I already have. That being said, has anyone had this issue before? I've seen stuff online claiming it could be a broken "forward apply band", but I'd think that if it was broken, it would never work, rather than not working SOMETIMES. Any help is appreciated, thanks.
[This message has been edited by Crazy_ones24 (edited 09-03-2023).]
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From how you've described the situation, there are indeed a few possibilities at hand regarding why your transmission won't consistently shift into third gear. But before considering those, it's good that you already checked the transmission fluid condition and level, as well as replaced the shift solenoids.
Do check if there's a transmission control module that's failing. Sometimes faulty electronics can cause sporadic behavior, the module can intermittently send incorrect signals causing inconsistent shifting issues.
There could potentially be an issue with the torque converter clutch. If the clutch or the solenoid that controls it is damaged, it could potentially interfere with the shift timing.
You mentioned the shift linkage. Have you inspected the shift cable itself? It could be stretched, frayed or otherwise damaged in a way that is interfering with its function.
The transmission valve body, which is the control center of the transmission, could be the issue. Over time, the valve body can develop leaks, wear down, clog up with debris or even fail outright.
Please keep in mind that a thorough, professional diagnosis is the most reliable way to determine the cause of your issue. I understand the frustrations that come with an underperforming transmission—especially on a unique car like the Fiero—and I agree that it can be expensive and frustrating to rely on a shop for every problem, especially if they are rude and unhelpful.
Regarding the forward apply band, it's entirely possible that the band could be worn and not completely broken, which might allow for occasional correct operation.
Also, there were a couple of transmission options available to the 1985 Fiero – a 3-speed and 4-speed automatic. I'm assuming you're referring to the 3-speed, given your mention of 2nd and 3rd gears.
Remember, regardless of what the problem is, be extremely careful when delving into an automatic transmission as they are complex and precision engineered. Dealing incorrectly with even one small component can cause further issues down the line.
Good luck, and don't let this discourage your enjoyment of such a unique car! The SC 3800 is a fantastic setup once you iron out the issues. Click to see AI response
If you wish to do a 4T65eHD trans rebuild, I strongly suggest purchasing both the repair video and the manual. Good info on You Tube as well. Purchase a rebuild kit. There are many parts to contend with when rebuilding so its important that all new parts go back in the exact place that they were removed from. Use a cardboard template of the valve body when saving all the screws Take pictures after each rebuild step. A likely cause of the transmission not shifting into third gear would be to start with a test of the shift solenoids. Go slow with the rebuild, take it a step at a time and it should come out OK.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
[This message has been edited by Dennis LaGrua (edited 09-02-2023).]
Ok, thanks for the info. Any clue what that might cost? I thought I was ready to put the cradle back into the car but I decided to order a few more replacement parts while I'm here. I've already replaced the 2 shift solenoids, and pressure control solenoid. If that doesn't fix it, then I'll look into a rebuild. However, I think I may just purchase a GTP with a series 3 and swap out my series 2 instead. Have you rebuilt any transmissions? As a novice mechanic, do you still think I should try to rebuild mine myself?
Also, I've seen your car around on the forums, I'm very jealous, looks amazing! With your series 3, did you retain the drive by wire throttle, or convert it to a cable? Any idea which is easier?
