350 Turbo Locking up in L1 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-21-2009, 07:39 AM
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350 Turbo Locking up in L1

Hello, I'm hoping someone has had this happen to them before, or at least has a suggestion as to what is causing this problem.

My little brother and I have just attempted to rebuild our first 350 turbo (this is our first attempt to rebuild any automatic tranny for that matter). We purchased a DVD and a book on how to do this, and watched and read each several times before making the attempt. We used a B&M rebuild kit and purchased a new B&M torque converter - and filled the tranny with B&M trick shift fluid.

When we got the tranny back together and in the car and started up for the first time, the DVD said to put 1 quart of fluid in the torque converter, and 4 in the tranny - then let the car idle for 20 seconds and put in another 4 quarts - start the car back up and fill until it shows as being full. So we did exactly that, and had a total of 9 quarts in and noticed immediately something wasn't exactly right, because the dipstick shows as being approx 3 quarts over full. So, since our pan has a drain plug, we drained it back out until it showed the correct amount in the tranny. Then started the car and put it in reverse (on jack stands) and let it idle in reverse for 20 minutes to break in the new torque converter. If I remember correctly shouldn't a normal non-lockup 350 turbo hold about 12 quarts of fluid? Could it be that the stall converter (3000 rpm) that we installed in this tranny be the reason as to why it appears to be full with a little over 6 quarts?

When we got it back down on the ground, and did a test drive is when we noticed that we screwed up something. In Drive, the tranny takes off in 3rd gear, in L2 it takes off in second, and strangest of all, in L1 it takes off in first for about 1 or 2 feet and feels as if it has been slammed into park - locking up the tranny. We can then shift into L2 and it will take off again in second, and if we try L1 again the same thing happens again everytime.

So, I asked some friends and posted at a couple forums and everyone said that we have too much preassure going on in the tranny. Now, back when we pulled the tranny apart our DVD showed that there should be only 4 checkballs, but there were only 2. So, thinking we were doing the correct thing, we pulled a couple check balls from a scrap 350 turbo so that we could put all 4 checkballs back in. Now with everyone telling us that the problem is too much pressure, we figure it's probably the checkballs. So, to be certain that we have the correct checkballs in the correct places, as well as the correct seperater plates and gaskets, we purchased a B&M shift kit and installed it following the directions for a stage 2 (Street/Strip) install - which required us to drill 2 holes in the seperator plate and install only 1 checkball. We followed the instructions of the sift kit meticulously however, we still have the exact same problem.

Which leads me now to last night. I again called some more friends of mine and explained everything and one of my friends suggested taking the valve body from my sacrificial tranny and putting it into the tranny I'm working on. So thinking that would be a good idea, my little brother and I have completely disassembled and cleaned the valve body from the sacrificial valve body and it is ready to go in (however it's raining today so we'll probably wait until tomorrow).

Now I'm here hoping that maybe someone has had something like this happen to them and can tell me exactly what might be causing this problem - specifically the part about it locking up when it is in L1 - I've never seen that happen before and it's driving me crazy trying to figure out what could cause it. Could it be the manual 1st valve is stuck? Because I would think that would simply cause it to not go into first if that was the case. Remember, it goes into first when shifted into L1 - and pulls forward about a foot or two and then locks up. Anyone have any ideas?

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Old 07-22-2009, 02:19 AM
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This may or may not help you. > http://th350.netfirms.com/pages/7a2-09.jpg
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Old 07-23-2009, 07:06 AM
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Problem Fixed

Well, I had several friends suggest that the problem was with my valve body. So, we took the valve body from our donor/scrap TH350, and completely disassembled it and cleaned it and made absolutely certain that all the valves moved freely. We then put it back together and put it in the TH350 that we just rebuilt. And I'm VERY happy to say that fixed the problem.

My guess about the old valve body is that it might be warped. If I use a small screw driver, I can move the valves. However, we can not seem to free up the plugs on the side of the valve body, thus we can not dissassemble it. I've even tried tapping on those plugs with a punch and hammer (gently of-course) and they just don't want to free up. So, since we can't move the plugs, we can't remove the pins.

I'll probably just toss that valve body. But I wanted to post this to let everyone know that I did fix that problem and it was the valve body that was causing all the problems.



Oh, and one more thing.... WOO HOO I just rebuilt my first TH350!!!
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Old 07-23-2009, 11:17 AM
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i would have tried a bottle of seal conditioner in it

it will soften swell the valve seals etc

i have saved so many trannies that were basically dead over the years with the stuff.

works wonders usually.

the valve or seal that engages it was probably just sticky

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Old 07-23-2009, 12:33 PM
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Quote:
Originally Posted by fast68
i would have tried a bottle of seal conditioner in it

it will soften swell the valve seals etc

i have saved so many trannies that were basically dead over the years with the stuff.

works wonders usually.

the valve or seal that engages it was probably just sticky

this is a fresh built unit, conditioner is not going to get rid of a cross leak that is causing a bind.
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