Technical Transmission troubles

Hello everyone,
Its been YEARS since I've made a post, but I'm hoping someone can help me out.
I purchased a rebuilt TH350 from a reputable source. (I've used the same builder on a previous builds with no problems) Filled the torque converter with 1-1/2 qts, slid it into the trans and felt/heard the double "clunk". Bolted it up to the flexplate and installed the trans to the motor (250 inline 6).
I got the motor running and had the back axle on jacks to let the wheels spin freely (I hadn't finished my brakes at that time). The wheels rotated when I put it in all gears. All was looking good.

Later, I noticed I had a speedometer gear housing leak. Pulled the housing and a bunch of fluid came out. That was expected. Once I replaced the housing with a new bullet and O-ring, I refilled the trans with what I had lost. That was a few months ago.
I started up the truck tonight ('48 Chevy with Lokar floor shift) and was expecting to operate the truck under its own power, but nothing.

I checked the dipstick once it was all warmed up and idling. It registers just above the hot mark. I thought, maybe its not working because it's over filled? That would be strange, but I pulled the speedo bullet out again to drain some fluid. Nothing came out!! I stuck my finger in there and it was dry??

So I began to fill the trans fill tube with fluid, with a drain pan under the speedo housing hole. Once I heard the fluid running out and into the pan, I stopped filling. Reinstalled the speedo bullet and checked the level. Now its up to the wavy bends in the dipstick, way above the hot fill line.

Started the truck again, waited to warm up. The tires are off the ground again to see if I could get any wheel spin. Nothing. I went through all the gears several times, raising the RPM slightly in each gear. I left the dip stick out to allow any air to purge.

I'm at a loss here. I know these symptoms will happen if you don't have enough fluid, but it seems like I have way too much and no movement since the bullet swap. And, before the speedo bullet swap, the wheels did spin when I put it into gear back then.
Any suggestions would be greatly appreciated

 

vacuum module hooked up?

 

How much time passed between these two events? Hours? Days? Years?

 

Verify the shift linkage is moving the selector rod in the transmission…

 

did you put in the converter bolts ?

 

Tell us about your fluid level checking procedure. Is the engine running? do you remove the dipstick, wipe it dry, then reinsert it and then read the level?

If you're checking it with the engine not running, the dipstick will show a higher level than it should.

 

Thanks for the replies so far!

Fastcar: My vacuum modulator was NOT hooked up! DUH! However, I just hooked it up to the front vacuum port on my carb and no change.

Ebbsspeed: I would say about a week passed from the time it rotated the tires for the first time to when I noticed the speedo leak and replaced it.

Oldiron: I have triple checked the linkage for the Lokar is shifting the selector on the trans, and its functional.

Pete: Yes, I did install the torque converter bolts and rechecked them tonight! ha!

Squirrel: Yes, exactly. I wait till the 180 deg thermostat opens, checking with my laser thermometer. Leave it running and in park. Then I pull out the dipstick, wipe it clean, reinsert it all the way and then pull it out for a reading.

 

Fastcar: Also, I verified that the carb port was indeed vacuum. While running, I removed the boot and the motor almost died. Placed my finger over the port and it was sucking. Thats the port I plumbed it to.

 

Governor stuck ?

 

There are three things that have to engage (input shaft, stator support, and pump gear drive tangs). The important thing is that when you put the transmission up to the engine, it goes all the way snug, and there is still some play between the torque converter and the crankshaft, so that you have to slide the converter forward a little bit to get it to reach the flexplate. If there's no play in there, then the pump gear drive tangs might have been damaged. If there was play, then it should be ok.

also...how much fluid did you put in the transmission? It usually takes about 9 quarts plus what's in the converter

 

Only 2 steps into place? then bolted converter to flywheel before bolting trans to engine? Have to go with what Jim just said above and quoted below.

 

My drug addled mind ( it's medicine ) tells me I had problems caused by a broke spring in the vacuum modulator. Easy fix.

 

Is trans dipstick read the same running and not running pump is not sucking up oil could be pump or priming valve missing or not working. Early turbo 350 trans had a priming valve. You can ck that by putting a small amount of air pressure into dipstick tube to help pressurize system no more pressure than 5 lbs or putting a hose on dipstick tube and blowing into it. I use a heater hose and blow in it with car running in gear with somebody in car . Stupid but works.

 

My first step would be to put a pressure gauge on it and see if the transmission is building any pressure (it doesn't sound like it is). You should have about 65 psi at idle with full vacuum on the modulator; 175 psi with no vacuum on the modulator. In L2 and L1 you should see the minimum jump to about 95 psi. In reverse the pressure should be about 95 psi with full vacuum and 250 psi with no vacuum. If you don't read any pressure, the pump isn't being driven by the torque convertor hub. If you could get any pressure at all it should attempt to go into gear. With the car on jack stands the rear wheels may turn just due to the drag in the clutches.

One thing you mentioned is the convertor and 2 clunks. There are 3 things that need to index when you install a convertor, the input shaft spline, the stator support spline, and the front pump gear. I've always used the idea that if you can get your fingers between the rear of the convertor and the bell housing, something isn't indexed correctly.

 

My first pressure reading should be in drive.

 

Update:
I took out the governor and it was stuck! I freed it up and it appears to be working now. I reinstalled it, warmed up the engine, but it still doesn't move the tires! I'm wondering if I should install a new governor?
I could install a pressure gauge on it. Haven't done that yet.
What I meant about the 2 clunks is, the two flanges on the torque convertor shaft. One flange seats, rotate the convertor and the second flange seats. The bellhousing mated right up to the engine and the convertor mated right up to the flywheel. No shims or pressing/stretching things to fit.
As I said before, the tires were rotating earlier, and for some reason there not now.
Thanks for all the input and suggestions.

 

The governor being stuck will make it stay in low gear, it won't keep the wheels from turning.

 

Governors and modulators control up shifting. There is an engagement problem. A fully seated torque converter has three distinct clicks, thuds, or bangs to be fully seated. First is input, second is stator support, and third is front pump engagement. If you didn't get three, chances re poor or no front pump engagement and thus no pump pressure to cause engagement of low-reverse clutch or band and forward clutch.

 

This has always been the way I do it as well , regardless of tranny or manufacture.

a cheap and easy way to see if you have any pump pressure at all is to pull a cooler line ( the one going to the bottom of your rad is output , and see what kind of flow you have , put the hose in a 5 gallon pail , it WILL spray out with some force .

other thing I would do is have the car up on stands securely, and shift the trans right from the selector on the side of the tranny , it does not take much of a misadjustment to not grab the gears correctly .

 

new trans. take it to builder

 

In your original post you say you "slid it (the torque converter) into the trans, "felt/heard the double clunk", but then it says you "bolted it (the torque converter) to the flex plate and installed the trans to the motor". Which one did you do?, did you slide the torque converter on to the trans input shaft then install the trans onto the engine, or did you bolt the torque converter to the engine flex plate then install the trans onto the engine?

 

9-10 quarts if it was totally dry. The pan holds 2.5 to 3 quarts only. Don't run it too long with very little fluid in it or out it comes again.

Clearly, this is the over looked question. How much fluid was actually poured into the transmission? You can almost bet it wasn't shipped with fluid. And it does take a bit to fill the converter. Just saying, I think it's low on fluid. Add in a transmission cooler, longer lines, that's volume.

 

Squirrel: Thanks for that note, I appreciate it

Deucemac: In my original posting I should have been more clear. I slid the torque convertor over the splines, then pushed the convertor until I felt the shaft make contact. Then I turned and pushed the convertor until it mated into the final groove. I'm 90% positive its seated correctly. I would of said 100% before all this happened. Now, I'm not so sure. If it means pulling the trans, Ill need to do it just to make sure its seated like I think it is now.

Vandenplas: Excellent suggestion. Ill pull a cooling hose tomorrow after work. I'll also see if I can get a finger between the back of the convertor and the bellhousing.
The floorboard access panel is off and I can visually see the side of the trans shifting with the linkage. I checked on that earlier.

Junkman: Sorry for the confusion! I filled the torque convertor with 1 to 1-1/1 qts, then slid it onto the trans. I had the flexplate bolted to the crank already. I took both the convertor/trans combo and bolted them both to the engine/flexplate. Its possible I messed up something with that step. I think I need to drop it now just to make sure its 100% installed correctly.

Noel: Good point. I did just recently plumb in the cooler lines. But the stick is reading over filled. BTW, when I took off the governor cap, only a half quart spilled out. Not sure if that is more or less than typically comes out? Maybe just removing a cooler line and running it may purge trapped air in the system?

Thanks to everyones input. Tomorrow night, Ill pull a cooler line and run it. Then Ill check for finger clearance between the convertor and bellhousing. If those tests dont check out, I'll be pulling the trans.

 

Junkman: sorry again, I meant to type... between 1 and 1-1/2 qts...

 

FYI in case someone is scratching their head...
Short answer, no difference. I am not sure why Lokar sells TH350/TH400 dipstick under a different part # than their 700r4 version. I ended up with both and guess what? They are identical. Same length, same markings, same plug, same everything. I guess there is a chance that someone at the factory got it wrong and package them wrong (packaged a 700 dipstick in a th350/400 box). However, when I did index the Lokar dipstick against a standard GM 350/400 dipstick, the "low" mark on the Lokar was 1 inch too low...

I'm jus saying...no or low is still no go.

 

I had one in an OT Monte Carlo, I was on the road with my wife with her driving. She mentioned it didn't seem to be shifting into 3rd. So I drove it... as usual she was right. Then no 1-2 shift and finally it stopped moving. We were close enough to a Lee Myles, I walked over and they towed us in. It was a bad governor.

Most transmission shops had them on the shelf as exchange units, I guess they had the old ones rebuilt. On the stock cars, we would sometimes run a TH400 in 1st gear and it was necessary to wire the governor closed. Even with the selector in low, at about 5000 RPMs it would shift into 2nd so it wouldn't blow. Usually at the worst possible moment, like slowing in a turn.

 

OP,
Here is what I would do. Pull the return line @ the radiator,(upper line) start the engine and see if you have cooler flow. If you don't, unbolt the converter and push it all the way into the pump gear, then measure the distance between the flex plate and the converter mounting surface. It should be no more than 1/8 inch, you can shim it with flat washers. I have seen tolerance stack, where the converter would pull all the way out of the pump drive gear. Worst case scenario, pull the trans out, pull the converter and look into the pump and you'll see if the pump gear is damaged.

 

UPDATE: So last night after my last entry, I went out to the garage to test some things.

I pulled the upper trans cooler line off at the radiator. I wasn't sure if that was the right line or not. I figured if its the wrong one, then the radiator port will shoot trans fluid all over the front of my engine.

When I pulled the line, I had rags under it, expecting some fluid. It was dry. I put the line into a bucket and fired it up, nothing came out.

So, its pretty clear the converter is not seated fully to the pump gear. I also did a ton of research and found out there are tolerance measurements. Thank you Potshot for the measurement suggestions as well.

I'll be honest, when I put this together, I knew about seating the converter fully into the trans, (even though it appears I dropped the ball on that) but I didn't know about the tolerance checks.

I will make some reference marks and measurements as a base line before I unbolt the converter from the flexplate. Unbolt it and see if I can push it in further, into the pump gear.

Whether I can push it in or not, I feel like at this point I need to pull it out to inspect everything. And, since the front clip is off, I will pull the engine/trans combo.

Once its out and supported on the floor, I can get some good light and inspect all of the parts for scarring or shavings. I never heard any sounds from the trans during the few times I've test ran it, but I want to be certain. Better to replace parts and components now than some random day out in BFE.

I'll be sure to follow up with my findings. Thanks to all who have helped with this!

 

I'd do some triple checking of fluid level, first...