I have no issues looking for a reputable transmission shop but I always hate giving up a chance to save some money and learn something at the same time. Admittedly I have zero experience with transmissions but I am mechanically minded and typically successful when pointed in the right direction. I have a '65 Riviera with the ST400 transmission. Having said that, a previous owner removed the Switch Pitch fucntionality so today I guess it is really no different than a standard TH400. As for the issue...the transmission will not come out of 1st gear. Here is the background info. 1. From the time I purchased the car three years ago, the transmission would never kick into passing gear. I had a long list of things I had been working on and I never paid it much attention. The other day it kicked into passing gear for the first time but I could not get it to do it twice while driving the rest of the day. 2. The next day I went for a drive and it kicked into passing gear but when I stopped and then started again it wouldn't shift pass 2nd. I shifted manually through all three gears and then it acted normal for the next 10 miles. Then, when accelerating from a stop light it wouldn't shift pass 2nd again. I could shift it manually through all three gears but it would not shift automatically. 3. Took it out the next day and it would not shift pass 2nd. In addition, I could no longer shift through all three gears manually. 4. I had good vacuum but changed the modulator just to see if it would make a difference. I took it for a spin and now it wouldn't come out of 1st gear. 5. I dropped the pan and the fluid was clean. I pulled the valve body and removed all of the valves. There was a little bit of trash in some of the valves. I cleaned everything up and installed a Transgo kit and a new kick down solenoid while I was in there. 6. I put everything togther today and it drove perfectly. It shifted automatically through all gears without issue. I decided to put it to the test and pushed it. Down shifted perfectly but then would not shift back up to third. I stopped and then started again and now it won't come out of 1st again. Sorry for the long post but I'm a bit perplexed. It would seem this is a an adjustment of some kind since it shifted automatically through all gears today when I took it out. What is it about the down shift that would cause the issue I have? Let me know your thoughts! Thanks - Ron<!-- google_ad_section_end -->
Three possible problems.. 1. You have something coming apart, deposting trash in the valve body, sticking the valves.- Not real likely, but it is possible that a clutch is shedding material.. 2. Governor is sticky. It's under the side cover on the passenger side of the trans. If the valve body had trash in it, then it's almost certain the governor does too.. pretty simple to take apart, and clean, and put back together with a couple of 6 penny nails. I would swap out the governor for a known good one, if you have such a thing, and go from there. 3. Modulator valve is sticking.. it's behind the modulator. No low speed/off throttle downshifting back to first is typically the governor, or governor related. Upshift issues can be either governor or moduator related- no vacuum at modulator/defective modulator/sticking valve is the most likey cause of no upshift from first. I assume that at no time does it "neutralize", meaning it always stays in some gear. JW
It always stays in gear. I had the Governor out to replace the springs while I was installing the Transgo kit. Everything was clean and the weights moved freely. Barring a broken part, do Goveners go bad? I removed the Modulator Valve this afternoon and the area looked clean. It's hard to say how free the valve moves as it is difficult to work in and out when it is inside the case. I didn't have any issue getting the valve out though. I thought I would see more fluid when I removed the valve but just got a few drops. The oil level was low but I wanted to get the car warmed up before adding more fluid. Since my symptoms are still the same as before the valve body cleaning I don't think fluid is the issue. Not sure how I can diagnose the sprag as mention in the first reply. Since the transmission functions normally at times wouldn't that mean the issue is more than likely not the Sprag?
Usually a sprag allows a first gear no second but drive will work. Have you driven the car to high gear yet?
When I got everything assembled this morning I took it out for a drive and it shifted normal through all gears. Once I pushed it and it kicked down into 2nd is when the problem started again. This has been consistent since it first downshifted a couple of weeks ago. As mentioned in my first post, prior to a couple of weeks ago, the car had never down shifted on acceleration since I purchased it 4 years ago.
I've blown the sprag before. Try this to see if it is similar to what I broke. If you leave it in drive and you accelerate to a speed fast enough that it will shift to 2nd and/or 3rd and let off the gas, does it freewheel? Then, pull it into 2nd. Does it engine brake? That's the symptoms I had that was a sprag when it was fixed.
The only other oddball thing I can think of is that maybe the detent switch on the pedal is intermittently sticking, keeping +12v going to the detent solenoid when it shouldn't. Devon
I think the kick down switch at the carb may be the issue. I removed the Governor, took it apart and cleaned it. Not a spec of dirt to speak was noticed. Got everything back together and decided to disconnect the power to the kick down switch at the carb before my test drive. Wire came off of the connector so no doubt there is no 12v to the detent solenoid. I test drove the car and it ran perfectly. Nice crisp shifts at 2300rpm. I manually shifted into 2nd and back to 3rd on numerous occasions without an issue. I ran out of time to fix the wire to the kick down switch and will be out of town for a couple of days. I think when I get back I'm going to drive it as is for a few days and then work on the kick down switch again. If it locks up again I will replace the switch at the carb as it is sealed and I cannot get insde it to clean it up and adjust it. I will update you guys later in the week. Thanks for all the suggestions and assistance. Talking through this with you guys improves my sanity!
You could tell if it was the switch by unplugging it. It should shift through all the gears. You won't have passing gear and under acceleration it will shift early but will go through all the gears. Good Luck. Bob H.
Even if it's not the switch but instead the detent solenoid itself messing up from time to time, the problem would appear to be the same. The bad news is if the solenoid is the culprit, it's that much harder to diagnose. Devon
I replaced the solenoid while I was in there this weekend. It was only $12 and I figuered it would save me from dropping the pan again. Providing the 12v source is good, the only thing left in that circuit is the switch at the carb. Since the solenoid requires 12v to operate, if it locks up again I can simply open the hood and unplug the switch. As good as it ran today I just find it hard to believe that the trans is breaking down mechanically. The only difference today is that the kick down switch is out of the circuit.
Success! When the transmission was rebuilt by the previous owner they removed the Switch Pitch functionality. They installed a single spade case connector for the wire to the Kick Down switch instead of the dual spade connector for Kick Down and Switch Pitch control. The problem was that the wire now feeding the Kick Down switch was actually intended for the Switch Pitch control effectively feeding 12v to the Kick Down switch the majority of the time. This hadn't been an issue since the Stator Switch at the carb was dirty inside and not making contact. I had been adjusting the switch over time trying to see if I could get Kick Down control. I guess I messed with it enough to get it to at least make contact with the slightest bit of acceleration. Anyway, I disassembled the switch and cleaned it up inside. It is installed and adjusted properly. The wires to the transmission case connector have been swapped and the transmission is shifting perfectly! Thanks again for the help! Ron
But if it's a TH400 the kickdown switch is an electric switch from gas pedal to tranny in some cases. Not sure how this TH400 was retrofitted to this Rivvy though.
It's a '65 Riv with the original ST400, with the detent and variable pitch plunger switch next to the carburetor. Devon
I am having the same problem and would appreciated any help. Running a heavily worked 60 over 69 Buick 400 with a Switch Pitch TH400 out of a Sportwagon that was rebuilt in the 80s by me with a B&M shift kit and KB SP converter. I have a "window rattler" cam so needed the converter. It has always worked great with firm shifts and zero problems. I have it set up for auto shift in drive with the ability to hold it in gear and manually shift. Car has a 12 bolt Moroso Brute Strength rear with 4:88 gears (yea they need to go). I have checked the governor, modulator, changed filter, checked lines, kickdown and SP control and all is good. It may be time to drop the valve body and/or flush the system but I wonder if its really time for a rebuild instead. Here is the story. The trans wouldnt shift out of first in drive or manually from first. With the shifter in 1st it would stay in first to any RPM. If I manually shifted it there was no engagement and going back down into first would engage the band and brake the trans. Right before this happened the shift to second became very hard and long like a double shift with lots of wheel hop. At around that time, ONLY when the trans was HOT I also heard what sounded like a scraping noise (not a whine) at idle or slow speed in drive. I took it to a trans guy and he said the accumulator piston went and there were shavings in the valve body. Car ran great for 3 months and same thing exact thing happened, with the noise and super hard and long shift. I was driving the car to a near by shop in first gear to check it out and all of a sudden it started shifting again with no noise or problems. I changed the fluid and filter and all was well for another few weeks and then the same thing happened and once again it cleared up after driving it. Now the same thing happened again. Could it be that the crud from the bad part is still in the system and flushing it out would help? Or is there something going and when it gets hot its shedding particles and clogging up the 1-2 shift valve or VB? I have thought about getting a rebuilt TH400 but don't like the thought of a non-lockup converter and I don't want the hassle of switching over to one of the new GM lock up ones with all the changes needed. Only really driving the car on the street locally.
