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Losing 2nd Gear

2K views 16 replies 3 participants last post by  more cubes 
#1 ·
My 1-2 shift started flaring badly Thursday. It does this at very light part throttle driving and only got worse with additional throttle. It is fine in first and 3rd. I parked the car and will be checking line psi, codes and fluid level tomorrow but would like to know what else to look for if these are okay?

The car has not thrown any codes through the MIL and the fluid was at the correct level and clean prior to this. Some additional background info that may help:

1. The car has not been driven much over the last 5 years. It has about 1,000 miles over this time. I bought it and put maybe 200 miles in the last 2 weeks and worked great until now. Didn't worry too much about this when I bought the car as everything else is in such good condition and working excellent.

2. In the 6 or so full throttle 1-2 shifts I have done since owning the car, the 1-2 was solid for a stock tranny IMO. I drilled out my air box earlier in the week and was testing it out. I had one shift that actually chirped the rear tire and wondering if this had anything to do with it. I was surprised it shifted that hard and tried to see if it would do it again the next day and it was back to "normal". This could have been coincidental with me being low on fuel and I was slightly rounding a corner, both taking some weight off the rear. The 2nd gear issue happened two days later.

Sorry for the long post but want to make the most of my time at my buddy's shop tomorrow. I would love to hear your thoughts.

Bill
 
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#2 ·
Checked out the car this AM. There were no codes stored and the fluid level was correct. The pressures were at 65 in P, N, OD and 1st. It was only 80 in R. 2nd gear would start at 65 and jump to 95 after 3-5 seconds of being in gear and stay there. All pressures were checked at idle.

Hmm...
 
#4 ·
Thanks Joel. I misinterpreted #3 as being WOT anomalies and not part throttle issues. Oops! Thanks for taking the time to point this out- I will check this out.

I probably missed this too, but where is a good place to purchase an accumulator piston or spring if it is broke?
 
#5 ·
GM dealer, ebay, or local trans shop (they often have good used spare parts). If the accumulator bore is screwed up, you'll need a new one of those too.

Sonnax makes pinless accumulator pistons. They are a bit more pricey but very well engineered pieces.
 
#8 ·
I can't get the picture to post for some reason but here is a link: https://picasaweb.google.com/101627785150112841721/Wagon#5657972859149039138

It is a yellow spring (~.152" diameter) and the piston is cracked out around the center. The bore looks pretty good- there is some very light scoring in one small spot where I assume the spring must have come in contact with it. It is very slight but enough to where I should probably lightly polish it to be safe?
 
#9 ·
#10 · (Edited)
Yes, just polish it so it won't chew up the rubber seal.

On the parts you listed - yeah, looks great. That's what I would do. I would not use the TransGo boost valve. The one in my wagon did not last long before the line rise died off again. They are built to much looser tolerances than the Sonnax units.

Be aware that the Sonnax boost valve is tricky to install without shaving those o-rings. If you're careful, you can smooth/polish the steps that lead into the boost valve bore without putting shavings all in the trans. Sand/file/wirebrush, whatever you want to use. Then, use vaseline to help avoid any damage to the seals as you install the valve.
 
#11 ·
Hmm... have not used the Sonnax piece. Have not seen a big need to part with Transgo's .500 boost valve. But, Vince (formerly of FLT) used to customize some parts for me back in the day. Might have to investigate before the upcoming rebuild.
 
#12 ·
Well, I was able to get all of the parts yesterday and install them last night. Today I filled with fluid and went to test the trans and I do not have reverse. I am assuming I must have had a problem with the boost valve install? I used vaseline and installed it without shaving the o-rings or the case. Maybe I tore up the o-rings?:confused:
 
#13 ·
You probably just didn't get the boost valve retainer ring fully seated and so the whole valve assembly blew out the bottom when you put it in reverse. It's easy to fix. I bet if you take off the pan, you'll find the boost valve laying in the pan. GM put an intermediate land in there that can feel like you've got the ring fully seated, but you don't. That's gotten me before.

Not necessarily applicable to your case, but the other thing that can cause weak/no reverse after work in the pan is when somebody puts the valvebody back on but forgets to torque the three little 8mm bolts on that metal plate that fits between the valvebody and the case. Unfortunately they're basically inaccessible if the valvebody is already on. When I'm installing this, I usually use a valvebody bolt on each corner of the spacer plate to properly align the spacer plate across the entirety of its span, then torque those three bolts, then install the valvebody itself.
 
#14 ·
I have not had a chance to get back to this as of yet... I will be heading out of town again and it will be another week or so before I spend time on the car. I will be sure to post back with what I find. I do remember questioning the snap ring- there was travel of around ~3/16" when I pushed on the boost valve by hand. I did pull on the end of the valve with pliers to see if it would pop loose but I am sure this is not anywhere near the pressure the valve would see when running.
Bill
 
#15 ·
Well, I did not have the boost valve fully installed. It was still in the bore but I did not get the snap ring in the top land (looked to be hung up in the intermediate land).

On the test drive, I now have reverse but second gear is still slipping. It is better than before but any reasonable throttle on the 1-2 shift or while in 2nd gear causes it to flare.

I am re-reading the accumulator instructions, and as best I can tell, I did it correctly. I have plugged the accumulator housing with the checkball. Both springs were installed in the housing with the dome end of the piston towards the valve body. After finding the broken piston and spring, I was sure that this would have resolved the problem?
 
#17 ·
Just an update for Joel and anyone that was following this thread- the 2-4 band and drum was shot. I am getting everything else upgraded so it will hold up. The car should be back on the road next week with the new trans, gears, converter and tune.
 
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