Ok, I officially have the absolute worst luck in the world. A few months back, I went through 2 700R4's in my iroc in two weeks, and now I"m converting my firebird to Th350 with a 10 inch 3,200 stall converter. Got the tranny and conversion kit all set up today and yesterday, and big F'n suprise, guess what shifts like crap!! The guy swore up and down the tranny was golden, and I can't afford $400 for a rebuilt Th350, so I went on his word. It came out of a running car, so I drained all the fluid, put in new fluid and front/rear seals, and installed it in the car. The torque converter is a B&M 10inch 3,200 stall, brand new. So anyways, I spent the last two days straight under this damn car, get in it for a test drive...........shifts SOOOOOOOOOOOOOO soft and mushy at all throttle/speeds, heavy pedal, light pedal, doesn't matter. If I try to gun the car, it takes like 4 seconds to shift to the next gear, like a clutch slipping. I can't believe my luck is this bad. The only thing that I can think is that maybe the 10inch converter isn't supposed to be used with a stock TH350 with no shift kit. And one other thing, the vacuum modulater that came with the tranny is VERY strange. Its about the size of a beer can, and I can suck on the vacuum line and next get any pressure to stay in the line (ya know, try and see if it will hold my tongue with vacuum pressure.... So its either a combination of the weird/crap modulater and no shift kit+10inch converter, or I have yet again found a crap tranny to waste money on. What do you guys think? I would think that even without a shift kit and a 10inch converter it would at least shift firm, not so mushy and slow like it is now.

 

Depending on the condidtion of the internals it's totally possible for it to shift just as you described. I personally would by a new vaccum modulator for it to start with since it's cheap and effects shifting when you have it in drive. Next I would spend the money and get a shift kit. In HS we had good luck with the cheap B&M kits in junkyard TH350's-very easy to install, just read the directions. Hopefully for under $50 and a little of your time you can get this sorted out.

 

I should also add that tranny fluid seeps out of the vacuum modulater........would that cause soft mushy shifting??

 

Right there is your problem. There must be a small leak or possible diaphram failure in your modulator, there should be zero fluid coming from or through there period. Get yourseld a new one of those and see what happens. Hopefully this will cure your problem.

 

What the hell, put in a bottle of Lucas Stop slip $8. (cant hurt)

 

LOL, first he needs a new modulator as there should be no fluid what so ever coming through it. After he replaces that, then try the horse remedy before the shift kit. It's hard to say what the internals look like when you get it from somebody. You better call Lucas and tell them they have a new salesman and get paid for endorsement

 

Can I interest you in a case of Lucas "stop-slip" it works!

 

Actually, I used lucas in one of my first 700r4's and shortly there after I had worse problems than before which made me pull it and have it rebuilt, which lead to still not shifting correctly, which lead to trying Sea Foam which lead to winning races again The second rear end I blew up though I had 11 teeth missing off the ring gear and it howled like mad. Threw the cover back on and filled with Strictly Lucas oil stabilizer and it ended up being so quite you could hear a pin drop, actually quiter than the initial gear install I have pics if you want to see what hapens to these POS 7.5" ring gears and why they're junk

 

Bought a new modulater today, but I'm too lazy/tired/nervous to install it I'll do it tommorow along with a shift kit. If those two things don't fix it, then I'm gonna literarly start throwing things at the car. Knowing my luck, the tranny will be fixed...............I'll go make a pass, and the rearend will blow *** knows my car makes enough power to turn that rearend into junkyard food.

 

Yeah post a pic of the ring gear!

 

Chris, before you install the shift kit, put the modulator in first and go for a test drive to see how she feels. No sense in getting the cart before the horse. Did the guy you got it from install a shift kit in it? or was it hust a functioning stock TH350. You have the vaccum line to the modulator hooked up to a manifold vaccum point? Get'er working right so your at ground zero before you install the shift kit. This way you will know what's going on before you start the kit install and after if something does'nt go right.

Carrfixxer I took 3 shots, was missing teeth on one side of the ring gear and then on the opposite side. Third pic was a pic of the diff cover magnet with all the ground up teeth metal stuck to it.

 

Wow I never seen anything like that, was the pinion gear missing teeth too?

 

Nope, all three rearends I blew last summer were all victims of ring gear failure. Truthfully the first year I raced the 3.42 gear made it through a full season, the second 3.42 gear gernaded after about 5 races, and then I installed this 3.73 set and it lasted the rest of the season and blew up doing a burnout. I knew a 9" was going in before this season started so I was'nt too upset, but was mad I bought the good diff cover and welded the axle tubes and it still went bye bye.
When you pull your diff cover and the magnet looks like this and you find chunks of metal in the oil, your in for a bad day