What could cause second gear to just lock up on it's own? I caught a red light in traffic the other day, and as I slow down, the light turns green again. As the car downshifts into second from third, the back wheels locked up! Fortunately traffic got around me without incident. Anyway, when the car was slowed down to about 5 mph or so, the back tires unlocked as the car downshifted to first. So I pulled over to the side of the road, and looked everything over. Everything looked fine, and the car sounded fine. I tried taking off again, and as it shifted into second, it locked up again.

I wasn't driving the car hard when it happened or anything, so I'm really not sure why it would act up when it did. The transmission is a Yank Sportsman transmission with a Yank 3800 stall converter. This combo was in the car when I bought it, but from everything I can gather, it has less than 8k miles on it, so I'm kind of surprised anything happened.

The only recent mods that could have anything to do with it, is I put a 12 bolt in that didn't have the ABS option. Is there anything computer wise that could have locked up the rear brakes? My ABS light is on, but I don't think that would cause any problems. Mike at Yank suggested that maybe it could be the rear end locking up during the shift from 1st to 2nd, but after checking it out a little closer, the rear tires don't lock up, but its almost like the rear brakes engage.

So throw me some idea's here folks, I don't know much about auto transmissions.

 

Anything with the rear end or brakes doesn't seem to fit a second gear symptom to me.

I would first gather info like: Trans fluid color and smell, symptomatic hot or cold, manually shifting trans has what affect. ... I would then pull the pan and inspect. Normal metal on the magnet should be fine powdery shavings, no more than a pencil eraser's worth with nothing bigger than powdery stuff.

A trans clutch application guide will tell you what clutches are engaged and what ones are released during what gears.

... Ron

 

Thanks for the info Ron! Do you have any suggestions for where I can find one of these trans clutch application guides?

As far as the info: The trans fluid is red in color, and looks like virtually new fluid on the dipstick. The problem first occurred while hot, but it does it now when cold as well. Yesterday was a pretty busy day for me, so I didn't have time to try out the manual shifting, OR drop the transmission pan. I'll get you that info as soon as I get some free time.

 

Clutch application guide is in a Helms repair manual for your car, or most all transmission repair manuals for your trans.

... Ron

 

Sounds like either the 3-2 control or downshift shift valve got stuck, or the 3-2 shift solenoid is whacked. If you don't have proper 3-2 solenoid control, the trans won't release the high gear clutch pack properly. That can result in either a flare or a tie-up. Sounds like you experienced the latter - locking up the tires like you described..

 

Thanks for the tip Ron.

Brian- Your explanation makes sense. My question though, is why would first gear still seem to work normally if that were the case? Does first gear use the same clutch pack as perhaps third gear?

Also, I did some searching around the web to try and find out where the shift solenoid was, but the diagram I found doesn't help me a whole lot.
http://www.netgearhead.com/tech/gm/700r4.asp

 

It's all in the timing. When shifting from 3-2 the band has to be applied, and the 3-4 clutch pack has to be disengaged. If you grab the band too soon or delay releasing the high gear pack, it's going to tie up and stop the output shaft. If you delay grabbing the band and/or release the high gear pack too soon, you'll flare the shift. 4L60's have a pulse width modulated 3-2 downshift valve designed to gradually release high gear and gradually apply the band. If you have high-performance frictions that don't slip as easily (ie. Kevlar band) it can be a bit more likely to tie up.

 

Well, we tore into the transmission today, and found out where the problem was. I hope I word this right since I'm not familiar with the parts, but the support assembly for the low and reverse roller just gave out. The only thing that we could figure happened, was that at some point while I was running it a little hard, something partially gave. It was just a fluke that it locked up when it did. I'll include a picture of what it looked like from the top of the trans before we pulled out the broken pieces (not including the pieces in the trans pan).

Transmission pic (around 500kb)

 

Excellent graphics Smokin ... That's your low/rev sprag and it surely is toast. That little dude has got to hold back all those hard launches, the better the 60' time the more abuse it takes.

I know a "99" and later truck version 4L60E uses a "Wide" low/rev sprag. I'm not sure at this time if the car version 4L60E uses the "Thin" one like a 700R4 or if it has been upgraded too over the years. I believe there all a direct replacement upgrade!


That Low/Rev planetary you've got in there under that toasted sprag is definitely a 4 pinion ... a 5 pinion will definitely drop rite in there ... with a wide sprag and a 5 pinion carrier your 1st gear will definitely hold more torque than stock.

I'm interested in which sprag you had in there! ... I'm currently testing my TA Trans build set up in my Z-71 pick up and I for sure want the "Wide" sprag in my TA build.

... Ron

 

Ron, check your mail, the 5 pinion thing sounds interesting.

Also, here's a little more isolated picture of what broke.

Breakage