The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Engine & Drivetrain

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 10-01-2018, 11:47 AM   #1
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
TH350 Intermittent Engagement Questions and Troubleshooting Steps

Good morning, First time poster and been lurking for about a month now. So long story short, I recently purchased a 71 c10 305 with a th350. The owner that I purchased from swore up and down that the trans was good and he seemed pretty legit. I had it trailered to the house so that I could begin working on it and getting it running. The problem is that the th350 is not always engaging properly or may take a couple of seconds to engage. It seems to get better the more I keep messing with it but then it just goes to no gears, no reverse, no drive,d1, or d2. The trans had been sitting for a while but connected to motor.

Here is my troubleshooting:

1. Changed trans fluid and filter. Saw a couple of leaks with old pan and Speedo cable so I changed pan, filter, orings for bullet, and cooler. No leaks.

2. Started her up again, poured 4 qts of fluid in and let her run for about 5 minutes and kept checking fluid to make sure it was within the hot crosshatches. And it was even after shifting thru all gears. Tried to drive and it moved forward only with a bit of revs and reverse as well. Drove around the block and no gears at stop sign. Pushed back to garage.

3. Drained pan and pulled filter and there was some sludge , I assume from sitting for a while, put new filter on and repeated the fill shifting through gears. This time I put the rear end on jack stands. I had strong reverse, strong drive, d1, and d2. Wheel spinning away. When appoint brake I put it in park and left it running, checked fluid and it was perfect. Hopped back in and put it in reverse and go nothing. No drive either???

4. I started engine with transmission cooler line off and trust me, it’s pumping, made a mess all over floor. Repeated the rear on stands process with fresh fluid. Popped it in reverse and bam, wheels turning hard through all drives as well. After going through gears once and back to park, I get no gears again while on jack stands.


Is this th350 toast??? Is a break in process for a th350 that has sat? There are 0 leaks, I’m just confused as to why it able to go in gear on second and then 0 gears the next.
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-01-2018, 01:07 PM   #2
Chevyrestorerman
Account Suspended
 
Join Date: Aug 2018
Location: GBR !!
Posts: 144
Since you just bought the truck and most likely wanting to drive it I would just go ahead the pull the transmission out of the truck and go thru the damn thing. Most likely you will spend more time messing with it not knowing what you are doing and wasting time. In a hour after the truck is on jack stands you could have the transmission on the bench. Rebuild it and put it back in the truck so you do not have to worry about it leaving you on the side of the road. It’s what you want out of a truck, spend a few bucks and get it right.
Posted via Mobile Device
Chevyrestorerman is offline   Reply With Quote
Old 10-01-2018, 01:37 PM   #3
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Chevyrestorerman View Post
Since you just bought the truck and most likely wanting to drive it I would just go ahead the pull the transmission out of the truck and go thru the damn thing. Most likely you will spend more time messing with it not knowing what you are doing and wasting time. In a hour after the truck is on jack stands you could have the transmission on the bench. Rebuild it and put it back in the truck so you do not have to worry about it leaving you on the side of the road. It’s what you want out of a truck, spend a few bucks and get it right.
Posted via Mobile Device
One more question, if I put trans in reverse, it should only spin one way correct?
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-01-2018, 02:53 PM   #4
Chevyrestorerman
Account Suspended
 
Join Date: Aug 2018
Location: GBR !!
Posts: 144
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

Just like if you put it in drive the output shaft turns clockwise. I would hope if you put the transmission in reverse the output shaft will turn counter clockwise.
Chevyrestorerman is offline   Reply With Quote
Old 10-01-2018, 03:53 PM   #5
Myself
Registered User
 
Join Date: Oct 2005
Location: Northern Arkansas
Posts: 1,126
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

If it's been sitting for more than a few years it will need gone through most likely. There is a possibility that crud settled out in the VB and the valves are sticking. Try refilling and add a bottle of Trans Medic and running through the gears. Then if it's a no go, let it sit a day and try again. If it's still a no go, it will need torn down for overhaul.
Myself is offline   Reply With Quote
Old 10-01-2018, 04:06 PM   #6
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Chevyrestorerman View Post
Just like if you put it in drive the output shaft turns clockwise. I would hope if you put the transmission in reverse the output shaft will turn counter clockwise.

Sorry if I wasn’t clear.

The rear end is on jack stands. If I put the trans in park, I cannot rotate driveshaft either way.

If I put the trans in drive, and if the trans is not engaged, I can rotate driveshaft manually either way. Running or not.

If I put the trans in reverse, I can rotate driver shaft manually either way running or not.

I put some hydra trans in there and shifter through gears and same symptoms.

Trans seems to only engage for roughly the first 30 seconds or so before no gears. If I start the truck, and immediately put it in reverse or drive, wallah! Wheels spin. Go to another gear after brakes, 0 gears. Maybe time to pull.
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-01-2018, 04:07 PM   #7
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Myself View Post
If it's been sitting for more than a few years it will need gone through most likely. There is a possibility that crud settled out in the VB and the valves are sticking. Try refilling and add a bottle of Trans Medic and running through the gears. Then if it's a no go, let it sit a day and try again. If it's still a no go, it will need torn down for overhaul.
Yea when I drained transfluid again, there was a lot of black sludge, not metal though.
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-01-2018, 05:55 PM   #8
Chevyrestorerman
Account Suspended
 
Join Date: Aug 2018
Location: GBR !!
Posts: 144
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

Transmission is a sealed unit, how in hell can anything get into it...its not like a engine where the oil gets dirty....if trans oil is "dirty" is because its coming apart from within.... BLACK sludge ? how long was this sitting 10 years ? So if the vehicle sits for one year the ATF dont go bad....have you checked the date on a ATF bottle to see if it says MUST USE BY THIS DATE.....I dont think so. Like I said in previous post....pull the trans, and rebuild it...you will be happy you did. Enjoy!
Chevyrestorerman is offline   Reply With Quote
Old 10-01-2018, 06:00 PM   #9
Myself
Registered User
 
Join Date: Oct 2005
Location: Northern Arkansas
Posts: 1,126
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

I'm guessing the black sludge is clutch material. Probably has stuck parts thus slipping horribly and ruining clutches.
Myself is offline   Reply With Quote
Old 10-01-2018, 06:05 PM   #10
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Chevyrestorerman View Post
Transmission is a sealed unit, how in hell can anything get into it...its not like a engine where the oil gets dirty....if trans oil is "dirty" is because its coming apart from within.... BLACK sludge ? how long was this sitting 10 years ? So if the vehicle sits for one year the ATF dont go bad....have you checked the date on a ATF bottle to see if it says MUST USE BY THIS DATE.....I dont think so. Like I said in previous post....pull the trans, and rebuild it...you will be happy you did. Enjoy!
Pulling now!
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-04-2018, 11:20 AM   #11
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Good morning folks, pulled the transmission and discovered that I have a TH350C. My question is are there any internal difference between the th350 c and regular 350 during rebuild process? I know you can wire a switch to the electrical connection to lock up during crusuising and highly cruising, but i plan to plug thread the connection. And thoughts before I order the rebuild kit?
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-04-2018, 11:22 AM   #12
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Here is sludge in pan.
Posted via Mobile Device
Attached Images
  
GreyGhost85 is offline   Reply With Quote
Old 10-04-2018, 06:12 PM   #13
Chevyrestorerman
Account Suspended
 
Join Date: Aug 2018
Location: GBR !!
Posts: 144
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

That looks like the TCC is coming apart to me, if indeed its a TH350C.....

Input shaft is different, VB gaskets will be different as well. I would replace it with a 700R4 if it was mine. I just installed a 700R4 in my 72 c10 swb with 3.42 posi and it works great...

Last edited by Chevyrestorerman; 10-04-2018 at 06:21 PM.
Chevyrestorerman is offline   Reply With Quote
Old 10-04-2018, 06:49 PM   #14
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Chevyrestorerman View Post
That looks like the TCC is coming apart to me, if indeed its a TH350C.....

Input shaft is different, VB gaskets will be different as well. I would replace it with a 700R4 if it was mine. I just installed a 700R4 in my 72 c10 swb with 3.42 posi and it works great...

Interesting info, would you recommend further tear down of the transmission or have a shop inspect the tc? I have my mindset on rebuilding the 350 and replacing the tc right now. I found one pierce of metal in the valve body and about a peas size worth of sludge. Input shaft looks good, no wear or ground off splines.

I don’t plan to use the lockup feature and if I did I would use a switch. I know the trans will run slightly hotter with this feature disabled but I’ll accomadate a bigger cooler.
Posted via Mobile Device
Attached Images
   
GreyGhost85 is offline   Reply With Quote
Old 10-04-2018, 10:56 PM   #15
Myself
Registered User
 
Join Date: Oct 2005
Location: Northern Arkansas
Posts: 1,126
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

I'd run it with lockup, might as well gain mileage on roadtrips. Rebuilding is the same for all of them, clean thoroughly, inspect all hard parts, follow instructions, and reassemble. Get an ATSG manual, if there are updates or mods that should be made it's noted. I would run the lockup through a switch, an led in the dash and the brake pedal switch. I believe the original setup would have been vacuum switch and brake switch. Then you can turn it on off as you please and the led would remind you.
Myself is offline   Reply With Quote
Old 10-05-2018, 12:31 AM   #16
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Myself View Post
I'd run it with lockup, might as well gain mileage on roadtrips. Rebuilding is the same for all of them, clean thoroughly, inspect all hard parts, follow instructions, and reassemble. Get an ATSG manual, if there are updates or mods that should be made it's noted. I would run the lockup through a switch, an led in the dash and the brake pedal switch. I believe the original setup would have been vacuum switch and brake switch. Then you can turn it on off as you please and the led would remind you.
I dot really see myself taking roadtrips with this build but I am considering a switch
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-05-2018, 08:35 AM   #17
Chevyrestorerman
Account Suspended
 
Join Date: Aug 2018
Location: GBR !!
Posts: 144
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

GM offered different pressure switches, you can get a pressure switch to engage the TCC at a higher speed, so it would not engage the TCC to early. So in town driving would be better on the TC, no one wants a TCC locking and unlocking all the time while driving in town.
Chevyrestorerman is offline   Reply With Quote
Old 10-05-2018, 10:51 AM   #18
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
So during the continued tear down of this transmission I have discovered the following so far:

1. The accumulator spring is completely missing. I heard that this mod can cause harder shifts but also burn up the transmission.

2. The vacuum modulator valve is completely missing (the modulator gold vacuum connection is there). What’s the point of having the vacuum connection without the line?? Beats me

3. TH350C has 5 check balls in all of the stock locations. I don’t think a shift kit was installed.

I will be pulling pump and gears soon to inspect and start the rebuild.
Posted via Mobile Device
Attached Images
  
GreyGhost85 is offline   Reply With Quote
Old 10-05-2018, 02:02 PM   #19
Chevyrestorerman
Account Suspended
 
Join Date: Aug 2018
Location: GBR !!
Posts: 144
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

Transgo shift kit will instruct you to install 5 checkballs for the TH350C transmission which all 5 checkballs go into the case of the transmission. I have provided a pic of the TH350C transmission separator plate. In the pic will show you drill requirements along with checkball locations. Replace the TC and make sure you clean out the cooler and the cooler lines real good. The black stuff in the pan is pieces off the torque converter clutch. You can call it sludge or whatever but it’s the TCC coming a part
The TH350C torque converter is different than the t350. Make sure you buy the correct one. The TH350C will have the pilot type of input shaft.
Inspect all the hard parts for wear. Buy a master kit with steels, shift kit by transgo, intermediate band, and filter. This transmission likes its bushings replaced along with the thrust washers. It’s ok if the spring was missing in the accumulator. If you feel you need it. Put the spring in.
Attached Images
 
Chevyrestorerman is offline   Reply With Quote
Old 10-05-2018, 05:20 PM   #20
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Chevyrestorerman View Post
Transgo shift kit will instruct you to install 5 checkballs for the TH350C transmission which all 5 checkballs go into the case of the transmission. I have provided a pic of the TH350C transmission separator plate. In the pic will show you drill requirements along with checkball locations. Replace the TC and make sure you clean out the cooler and the cooler lines real good. The black stuff in the pan is pieces off the torque converter clutch. You can call it sludge or whatever but it’s the TCC coming a part
The TH350C torque converter is different than the t350. Make sure you buy the correct one. The TH350C will have the pilot type of input shaft.
Inspect all the hard parts for wear. Buy a master kit with steels, shift kit by transgo, intermediate band, and filter. This transmission likes its bushings replaced along with the thrust washers. It’s ok if the spring was missing in the accumulator. If you feel you need it. Put the spring in.
Thanks a ton. I would have never guessed that a shift kit was in place. I’ll try to get some more pics of the internals to post just in case this thread helps someone else in the future.
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-05-2018, 05:26 PM   #21
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Chevyrestorerman View Post
Transgo shift kit will instruct you to install 5 checkballs for the TH350C transmission which all 5 checkballs go into the case of the transmission. I have provided a pic of the TH350C transmission separator plate. In the pic will show you drill requirements along with checkball locations. Replace the TC and make sure you clean out the cooler and the cooler lines real good. The black stuff in the pan is pieces off the torque converter clutch. You can call it sludge or whatever but it’s the TCC coming a part
The TH350C torque converter is different than the t350. Make sure you buy the correct one. The TH350C will have the pilot type of input shaft.
Inspect all the hard parts for wear. Buy a master kit with steels, shift kit by transgo, intermediate band, and filter. This transmission likes its bushings replaced along with the thrust washers. It’s ok if the spring was missing in the accumulator. If you feel you need it. Put the spring in.
Are all transgo kits going to be the same?they are pretty cheap on eBay like 30$
Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-05-2018, 10:00 PM   #22
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

Posted via Mobile Device
GreyGhost85 is offline   Reply With Quote
Old 10-05-2018, 10:04 PM   #23
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
I took everything apart, all I found was a spot of rust and diss regraded paper gasket behind the center support. Roller sprays were a little beat up and I plan to replace them both during the rebuild. I’m really thinking the it was the tcc and simply replacing that would have maybe resolved the issue. But since everything is apart, might as well rebuild it strong for years to come.
Posted via Mobile Device
Attached Images
 
GreyGhost85 is offline   Reply With Quote
Old 10-07-2018, 12:53 AM   #24
Chevyrestorerman
Account Suspended
 
Join Date: Aug 2018
Location: GBR !!
Posts: 144
Re: TH350 Intermittent Engagement Questions and Troubleshooting Steps

Quote:
Originally Posted by GreyGhost85 View Post
Are all transgo kits going to be the same?they are pretty cheap on eBay like 30$
Posted via Mobile Device
If you are needing a shift kit for your TH350C than the SK350 transgo kit will work for you. I have asked before on this forum which shift kit to use and the transgo kit seems to be a poplar choice. There are other companies that offer shift kits like B&M, Superior, and Sonnax. I am not sure which one is the best one for you, I think its how you plan on using your vehicle. If the engine is stock it seems that the Transgo kit is used in a lot of shops to recalibrate the VB in not only TH350's, but also in 4L60E and 4L80E's using the correct shift kit for each type of transmission. Every shop I talk to installs a shift kit in their rebuilds.
Chevyrestorerman is offline   Reply With Quote
Old 10-08-2018, 12:26 PM   #25
GreyGhost85
Registered User
 
Join Date: Oct 2018
Location: Dallas Texas
Posts: 113
Quote:
Originally Posted by Chevyrestorerman View Post
If you are needing a shift kit for your TH350C than the SK350 transgo kit will work for you. I have asked before on this forum which shift kit to use and the transgo kit seems to be a poplar choice. There are other companies that offer shift kits like B&M, Superior, and Sonnax. I am not sure which one is the best one for you, I think its how you plan on using your vehicle. If the engine is stock it seems that the Transgo kit is used in a lot of shops to recalibrate the VB in not only TH350's, but also in 4L60E and 4L80E's using the correct shift kit for each type of transmission. Every shop I talk to installs a shift kit in their rebuilds.
One more question chev, you have been a tremendous help btw, I did some research on this and could only find a few items that said it was normal but wanted to confirm. During cleaning of the transmission housing/case there are holes that appear to be cut out or punched out. Is this normal? I threw a pic of the pic in there as well.
Posted via Mobile Device
Attached Images
    
GreyGhost85 is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 03:24 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com