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post #1 of 7 (permalink) Old 10-11-2015, 01:05 PM Thread Starter
 
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Transmission help

Hey guys, looking for a little bit of knowledge on my TH350. Maybe some of you have experienced what it going on and can share with me what you think the problem may be.

Car has a Pontiac 400 with a TH350 from a 70 firebird. To my understanding it was rebuilt before it was put back into the car roughly 2-2.5 years ago, where after that it just sat. Before I brought it home, all we really did was make sure it shifted well, and that it moved forward and backwards since it needed wheels, tires, and a legitimate drive shaft before it could really be tested on the road (putting power through the drivetrain)

I had a point while it was in storage where it lost quite a bit of tans fluid, but I chalked it up that maybe I added just a bit too much and it bled out through the air tube on the upper left side, cause it stopped and I basically topped it to where it needed to be and then no problems and since I was able to move the car around, basically idling going through R-N-D, it moved without issue other then it seemed to really have to think to find R. I finally decided to try and drive it now that it was registered as I needed lug studs replaced. In my was to the shop (merchants tire), the car was running really rough, had a difficult time making it up a hill out of the storage area, I thought maybe it was a timing issue. I got gas, gas tank then fell out and it was towed the rest of the way to the shop.(merchants) It sat there for a few days, had the studs replaced and gas tank rehung, no signs of trains fluid at all.

Now I'm at the point where I will try again, to get it to the shop for exhaust. Roughly 5 miles away. Pulled out of merchants and it died in the middle of the road Got it fired up and started moving, it ran sluggishly at this point but nonetheless it went. It definitely did not feel or move like it had a 400 under the hood, but I was able to get it to the exhaust place and was moving along around 35-45 mph. I got a mile from the shop and suddenly it seemed like it lost the little power it had. Pull into the parking lot, and after speaking with the owner of the shop, I notice trains fluid leaking out. Long story short, it lost a just about half of the trans fluid, was towed back to the storage since it was DIW.

I worked out a plan with a good friend of mine to drop the trans and replace all the seals and to check the timing on the motor. It sat in storage for about a month. Towed to his place dropped the trans, here's where it turns to the suck. The trans pan, had about an inch of caked sludge/clay, just nasty gunk (they could've used it as the prop clay in Ghost for making pottery) I would've taken a picture of it if I could've. So finished the seals and slap it back in the car, refill trans, and let it sit over night to see if it leaks, it did not.

Now it's time for another test drive, cycle through the the gears, flawlessly. Goes forward and reverse easily no more issues finding the gears, through idle that is. I back it out of the drive way, and start to give it gas and it just won't move, there is no power past idle. Rev higher and higher and the motor just dies. Repeat a few times and nothing, just no power to get it to move at all, the end of his driveway is on a hill. Throw it in drive and I managed to idle it back into the driveway.

So after that long story. The car moves forward and backwards fine, but there is just no power to be had at all once I put my foot on the throttle. Fluid is staying the car now. After discussing the possibilities, my friend and I have come up with a few conclusions. I will also say that, it is a good possibility that the motor and trans was caught in that flood that happened in TN awhile back before it was in the car. I'm not certain.

Torque converter is bad
Torque converter is filled with that gunk/clay sludge
Transmission is filled with that gunk/clay
Transmission was never rebuilt and everything is worn out for being nearly 50

I would love to hear from you guys in your experiences or knowledge. Recommendations, please.

Sorry for the long read.
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post #2 of 7 (permalink) Old 10-11-2015, 07:05 PM
 
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Time for a transmission rebuild & new torque converter. The gunk in the pan may have been clutch material. Trans fluid is a cleaner. If the bands were shot and you just put in new fluid, there is a good chance the fluid washed off all the remaining gunk/varnish that allowed the car to move.

A rebuilt TH-350 should be reasonable, but I would add HD bands, clutches, and a good shift kit if I had it rebuilt locally. The 400CI has a lot of torque and that is why they had the TH-400 behind it. The TH-350 is for lesser HP/torque cars.

Might be easier to buy an aftermarket trans with all the good stuff already in it (or a complete HD kit if you rebuild it locally). Also, you install a new torque converter at the same time. I think I would also ad a trans cooler and not trust the cooler found on the radiator as it may be all gunked up and not doing its job - unless you get it boiled out. But I still prefer an add-on trans cooler for insurance.
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post #3 of 7 (permalink) Old 10-11-2015, 09:39 PM Thread Starter
 
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Originally Posted by PontiacJim View Post
Time for a transmission rebuild & new torque converter. The gunk in the pan may have been clutch material. Trans fluid is a cleaner. If the bands were shot and you just put in new fluid, there is a good chance the fluid washed off all the remaining gunk/varnish that allowed the car to move.

A rebuilt TH-350 should be reasonable, but I would add HD bands, clutches, and a good shift kit if I had it rebuilt locally. The 400CI has a lot of torque and that is why they had the TH-400 behind it. The TH-350 is for lesser HP/torque cars.

Might be easier to buy an aftermarket trans with all the good stuff already in it (or a complete HD kit if you rebuild it locally). Also, you install a new torque converter at the same time. I think I would also ad a trans cooler and not trust the cooler found on the radiator as it may be all gunked up and not doing its job - unless you get it boiled out. But I still prefer an add-on trans cooler for insurance.
Thanks for the reply so quickly Sir!

That's what I was pretty much afraid of, but nonetheless agree with as well. I do have the option to swap to a 400 which I can probably just send that off to be rebuilt in leiu of the 350. As you suggested as well adding the little extras for for security.

The radiator I have is brand new rated to 650 hp with a trans cooler built in, and aside from the moving it around back and forth and that 4-5 mile stretch I drove, is it possible that the clutch material got into the rad and gunked it up as well? Any of the fluid that drained out when I removed the trans lines was clear and translucent, but that not necessarily and indicator that none of it is in there, maybe the pump itself was backed up enough that none of it would flow through the filter. Just trying to grasp an idea of how far I should go with worrying, in regards to the radiator.

Also it shows you're out of Gastonia, NC. I'm just outside of Greensboro, so if you know anyone you highly recommend, I'm all ears. Thanks again!
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post #4 of 7 (permalink) Old 10-12-2015, 07:53 PM
 
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If you have the new radiator, I would not worry. If it was the original, then it would be a concern.

Don't have any recommendations on a rebuilder for the TH-400. You should not have any problems finding a shop as the modern day 4L80E overdrive transmission is an outgrowth of the TH-400. I would simply check around or pop in to your local engine rebuilder as they usually handle some race engine stuff and may be able to steer you to the right shop - drag racers know where to go.

Like I said earlier, you want to make sure you get a shop who will install quality parts. I would also install the Trans-Go shift improver kit TransGo THM 400, 3L80: 400-1&2 rather than purchase a new/aftermarket valve body which you really don't need to spend the money on. You can purchase this at most online suppliers, Summit, Jegs, etc..

You can go stock on the converter or aftermarket with a slightly higher stall for some good take off acceleration. I would not go any more than 2,500 max and you want to make sure that you get a "tight" converter versus a "loose" converter. "Tight" means less slip, less heat put into the trans/fluid, better gas mileage. It doesn't slip under light to moderate throttle, but will come alive as it is supposed to under full throttle where you want it to work. Many vendors sell these. I went with a torque converter from Edge Racing on my brother's Mopar 360 Six-Pack build. Works great and is still going several years later with no problems. They offer street converters. It is a "tight" converter. They want you to fill out all the info about your car as they will then custom build it to your ride so you know it will work for you - so not quite as generic as other makers. Mild Street Edge Converter for GM TH400 Transmissions [MSE-TH350] - $254.50 : Edge Racing Converters, More Horsepower with More Torque Guaranteed!

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post #5 of 7 (permalink) Old 10-13-2015, 09:10 PM Thread Starter
 
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If you have the new radiator, I would not worry. If it was the original, then it would be a concern.

Don't have any recommendations on a rebuilder for the TH-400. You should not have any problems finding a shop as the modern day 4L80E overdrive transmission is an outgrowth of the TH-400. I would simply check around or pop in to your local engine rebuilder as they usually handle some race engine stuff and may be able to steer you to the right shop - drag racers know where to go.

Like I said earlier, you want to make sure you get a shop who will install quality parts. I would also install the Trans-Go shift improver kit TransGo THM 400, 3L80: 400-1&2 rather than purchase a new/aftermarket valve body which you really don't need to spend the money on. You can purchase this at most online suppliers, Summit, Jegs, etc..

You can go stock on the converter or aftermarket with a slightly higher stall for some good take off acceleration. I would not go any more than 2,500 max and you want to make sure that you get a "tight" converter versus a "loose" converter. "Tight" means less slip, less heat put into the trans/fluid, better gas mileage. It doesn't slip under light to moderate throttle, but will come alive as it is supposed to under full throttle where you want it to work. Many vendors sell these. I went with a torque converter from Edge Racing on my brother's Mopar 360 Six-Pack build. Works great and is still going several years later with no problems. They offer street converters. It is a "tight" converter. They want you to fill out all the info about your car as they will then custom build it to your ride so you know it will work for you - so not quite as generic as other makers. Mild Street Edge Converter for GM TH400 Transmissions [MSE-TH350] - $254.50 : Edge Racing Converters, More Horsepower with More Torque Guaranteed!

Thanks for all the info and help! I'm trying to find someone in my area who is reputable and intelligent when it comes to rebuilding them. I would prefer to stay locally, so if any issues arise, i'm not spending $$$ to ship a trans back. After doing some research though, i may stick with the TH350 and build it up, given that i just replaced so much on it, and i really do not want to have to buy another drive shaft and drill into the frame to move the cross member back. One shop i called told me it would be anywhere between $650-1600 depending on what they find... (would've rather he just asked how deep my pockets are)

As you said i want something done with quality work. I'm not planning on racing the car, i just want to be able to sleep at night knowing come the weekend, the transmission won't be on my list of reasons why the car won't move.

Currently, im looking into TCI transmissions, but the reviews i have found, literally have me terrified. But for the most part, the reviews have been around 4 years old.
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post #6 of 7 (permalink) Old 10-13-2015, 10:04 PM
 
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I too, had problems with TCI stuff. If you are going to spend that much on a trans, there are guys who build some really good TH350's and TH400's. Nowadays they have 36 element sprag assemblies for the TH350, and even spragless models. PROPERLY built, these TH350's will take all you can dish out, on the street. There are LOTS of 10 sec drag cars running these TH350's now. As mentioned, there is usually one or more trans guys who builds 'em for local drag racers, who can build a good one for you. It will at least save you the shipping charges. Will probably save several hundred, total. My trans guy, who was also a Pontiac drag racer, built my last TH400, with a 34 element sprag, for $550.

CoanRacing.Com | COA-31101-4 | "PRO-STREET" AUTOMATIC W/ HEAVY DUTY 36 ELEMENT SPRAG (STD.PATTERN, BUICK, OLDS, PONTIAC 6" EXT.)

http://www.jakesperformance.com/TH350.html
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post #7 of 7 (permalink) Old 10-15-2015, 10:32 AM Thread Starter
 
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I too, had problems with TCI stuff. If you are going to spend that much on a trans, there are guys who build some really good TH350's and TH400's. Nowadays they have 36 element sprag assemblies for the TH350, and even spragless models. PROPERLY built, these TH350's will take all you can dish out, on the street. There are LOTS of 10 sec drag cars running these TH350's now. As mentioned, there is usually one or more trans guys who builds 'em for local drag racers, who can build a good one for you. It will at least save you the shipping charges. Will probably save several hundred, total. My trans guy, who was also a Pontiac drag racer, built my last TH400, with a 34 element sprag, for $550.

CoanRacing.Com | COA-31101-4 | "PRO-STREET" AUTOMATIC W/ HEAVY DUTY 36 ELEMENT SPRAG (STD.PATTERN, BUICK, OLDS, PONTIAC 6" EXT.)

http://www.jakesperformance.com/TH350.html
Thanks oldskool!

Yeah, after sourcing other options I managed to find a guy who's professional job is rebuilding them, but he also does it for cash on the side for special cases, like mine. States he can do it for 750-800 including a new torque converter. Waiting on some more details before I pull the trigger. I want make sure he knows it's a Pontiac motor and that it needs to handle no more than 500 for when I make upgrades down the road, reliably though. Gives me a one year warranty, opposed to the 90 days offered by tci. I just feel more comfortable with someone locally, opposed to online, where they can really stick it to me, $1600 later.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

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