Hi Steve, try removing the vacuum modulator and make sure the valve is moving freely in the bore. If it is, unscrew the modulator adjuster and see if it any different. Scott Pettit
I pulled the valve body out of an old turbo 400 in my shop so I could swap it in to see if I could fix the problem. First I found a fair amount of clutch material in the my transmission pan, not a huge amount but more than I would consider normal for only having about 1000 miles on the car. More troubling, I found that there was no accumulator spring behind the accumulator piston in the valve body. The stock valve body of course has one. Is there any reason for leaving this spring out of the valve body? Could this be causing my problem???
The spring is removed to firm the shift, usually with other mods. There are two types of detent solenoids used, one uses a steel gasket and the other does not. A little mixing of parts could contribute to what is going on. Did you remove the modulator and see if the valve moves freely?
Mostly the stuff the other guys suggested to check out (gov lines, modulator/vacuum issues, governor, detent wiring, etc). There were changes to the valve body gaskets and they shouldn't be swapped ,,,, something like that done in the build could be difficult to find. Is there any warranty from the builder? Did the trans freewheel if you let up when it didn't shift and coasted down?
I just finished swapping the valve body, installed a new kick down solenoid, checked that the proper gasket was inplace, swapped governors again, confirmed that the modulator valve moves freely. This transmission has never shifted from 2nd to 3rd under full throttle and it still wont upshift from 2nd to 3rd unless I lift off the throttle first. I tried with the kick down switch plugged in and with it dissconected. Anyone want to buy a buick cheap. I have officially lost my mind (and most of my money) on this project.
Did this valve body have the accumulator piston and installed? That is the accumulator for the 2-3 shift.
I removed the spring from the accumulator on the replacement valve body per the shift kit instructions.
This has to be a bummer of a headache for you. I'm assuming the sealing ring was still on the piston. Maybe the shift is actually taking place but 3rd gear not holding? Maybe it holds enough for part throttle but not WOT?
I pulled the trans out of my car today. I only got a chance to pull the forward and direct clutch housings. I was hoping to see some obvious damage to the intermediate sprag, but nothing obvious. I will dig deeper into this thing this week and update as I go along.
here is a response I recieved from another forum.... Usually that problem is governor related. If your switch pitch is really old,those transmissions used a governor with a different type of governor gear. The early gears had a tit sticking out of the end of the gear to locate the governor in its bore, the newer governors have none but there is a steel dowel that was installed into the trans case and the governor gear has a hole that goes over the dowel for location side to side. You may have a late governor in an early case . Other problems could be a plugged governor filter located in the governor feed tube at the case or in the valve body. The last would be a badly worn governor bore or trash preventing the governor spool valve from functioning properly.
I'm no trans expert, but from the rebuild I did on mine I remember one thing.......the main pressure goes up in detent to make later shifts. In other words, at full throttle, when the solenoid is energized, something happens that causes the main pressure to go high, making later and firmer shifts. Perhaps they installed too heavy a spring in the pressure regulator on the front pump? (That's that fat spring that's about 2 or 3" long). One more thing......could the modulator valve be installed backwards? Just a thought.......try installing a stock pump spring, (black), you can do that without removing the valve body if I remember correctly. I had to do that b/c the heavier yellow spring made my part throttle shifts firmer than I liked. The lighter spring had no effect whatsoever on full throttle shifts, still chirps the tires. :Brow:
Hi Joe, I fully understand what you are saying. You are right that higher line pressure will 'hold' the gears longer. However, I did change the spring out in the fall while I had the engine out-no help. I pulled the modulator valve out tonight, it was not in backwards(that would have been tooooooo easyou: ) Steve, I did check the governor bore also (easier to get a good visual with the trans out)-it and the governor valve look ok. (I already swapped governors) It does act just like when the governor gear strips out though. I found out the hard way about the first and second design governor gears. I think I will take a peek at the filter tomorrow night. I have the valve body in the truck so I can 'air check' the valves tomorrow. They all seem to move freely so far, but what the hell, I'll air check them as long as the valve body is already out.
Once I can get under the car again I am going to try removing the governor filter. It makes me wish I had a drain plug in the pan. It's such a mess draining it by dropping the pan.
Once you drop the pan, I think B&M sells a plug kit you can install. This would help you next time-at some point I am sure you'll need to drain the fluid again. I pulled the valve body apart, nothing damaged, loose, or stuck. Although the gasket between the valve body and the seperator plate is questionable, a small tear near the accumulator that allows the gasket to drop slightly into the passage. I am not sure if this is a cause of the issue but it can't be helping anything. I also have pulled the second gear clutches, band, sprag, etc...nothing looks even questionable. I have to dig into the governor filter and start checking passages. I have been picking at it between cars at work so my pattern is a little off. Anyhow, I have ruled out more stuff, I would have liked to have found something completely 'blown up' but that would be to easy. Maybe tomorrow will find something more concreteo No: o No:
Well, I finally got the trans back together today. Every component fought with me going back together. It took all afternoon to get the danm thing together. Unfortunately I found nothing major wrong with it. Some slight pitting on the center support, but it looks like it is higher than the lip seals seat. I did find the fretting washer had been left out under the center support, I ended up changing center supports and this took care of the pitting and need for the fretting washer(washer only used if thickness of notched area is .xxx"-smaller than the other style cneter support). No burnt clutches, or bands. No failed/failing components. No sticking valves, nothing. There is one possible cause that I found. Appearently the valve body was replaced during one of the earlier rebuilds and one modification had been left out-locking the 1-2 acumulator valve. I installed a shim/spacer and will see if this helps. I did not do the earlier rebuild/modifications so I am hoping this is all there was left undone. As I said it had worked very well for several years, I can't remember when it started acting funky though. It may have been after the rebuild when I lost the convertor though. o No: I still need to swap the 'new' heads and roller rockers on the motor before taking it out. Hopefully tomorrow will be a very productive day
i finally got the car running, the trans now shifts into second as it should under wide open throttle. I only got about 3 miles on the car last night before turning in for the night and it looks like rain for the next 4-5 days. I am not sure what exactly caused the concern, but I would guess that it was the spring I removed from the valve body and replaced with a steel tube/shim. That is all for now.
Mine shifts 1-2 fine under full throttle, just no 2-3 shift under full throttle. I have been thinking of trying to manipulate the vacum to the modulator to see if that allows it to upshift. It seems that once vacum rises it will upshift. I might buy a hand operated vaccum test tool and plumb it to the modulator and apply vac to see if that allows a full throttle upshift from 2nd to 3rd.
Do you have an adjustable vacuum modulator on it? Most rebuild kits include the adjustable type. You can use a 'pocket' screwdriver to adjust it by removing the vacuum line and turning the inner valve in and out. In should increase the pressure/rpm, out should decrease it. I think I still have atleast one new one here. If you want it you can have it for the cost of postage from 06033. I think they are about $15 at the parts store, but check with them first, it has been quite a while since I have bought one seperate from a kit. Also make sure your manual linkage from the shifter to the trans is 'exact' with no play in it, this can cause funky stuff to happen as the valve does not seat fully initially, if at all.-Just a quick check to put the possibility out of the mind. Keep me posted to what you find.
