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Old 07-12-2018, 05:05 AM   #1
Mike_The_Grad
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Th350 done for???

1972 c10 350/350 LWB
I rebuilt the engine back in 2014. I have about 25k miles on it since then. I didnt touch the th350 other than a filter and fluid change. At that time the trans had about 85k miles on it. Engine bored .040 over, flat top "eyebrow" pistons, comp cams XE250H Hyd.flat tappet "RV" cam, 1.5 prw roller tip rockers, edelbrock performer intake, rebuilt stock Qjet 4MV from '72, reman "882" heads, hedman headers, super 40 3" true duel flowmasters, stock 3.08 rearend, u joints and center support bearing wear replaced last year, new prothane and energy suspension motor/trans mounts.

Replaced the detent cable with a plastic sleeve type OER brand ( I guess they dont make the metal sleeve type anymore. Not happy with it. Leaks like a sieve just sitting there on level ground.) Trans leaks from 1-2 accumulator cover, vacuum modulator has black and red band and is adjustable from autozone about 3 years ago. Just replaced the pan gasket with a felpro one, found one of the filter screws in the pan, fresh fluid after straightening pan rail, new derale trans cooler mounted in front of everything supplied by stainless hardlines, trans fluid does not enter the radiator at all, because i dont trust the internal cooler's integrity.

It's been 100+ every day around here since last Thursday. On that first day my engine coolant gauge inside the truck got to about the half way point, never got stuck in traffic but I do have a pretty steep grade about a mile long on my way home from work (6% grade).
I used to put a quart of fluid in the trans once a month or so about 2 years ago, now I put 3 quarts in it in the last 2 weeks. Always catching it right about the "add a pint" line. On Sunday it was 107 outside, I had driven the truck for about 20 minutes easy going, then I was stuck at 2 traffic lights in a row for what seemed like an eternity, parked the truck to get the lady some frozen yogurt, tried starting the truck about 5 minutes later, no go. Cranked but wouldn't run. Removed air cleaner, worked the throttle a couple of times to try and get the fuel vapors out, went and left the cleaner off and the truck started, replaced cleaner drive the 1.5 miles home. Drove ok. Temps were a little cooler yesterday and today. Fresh tank of 91 on monday evening and truck was lovin it. I was cruisin, took the long way home. Stoplight with a straight and clear lane, mashed that pedal til it wouldn't go anymore, truck launched and I was happy as hell and impressed to say the least, but that's when it all changed. No obvious noises, no crunching, scraping, banging, probably wouldn't even have been rememberable except that I noticed the truck no longer had that snappy response to my pedal efforts. Revs started going higher before shift points, which I thought was a good thing( staying in the power band longer) so much to the point that today I had 1/4 tank of gas left after maybe 80 miles of driving total. Usually I can drive 80 mph and have my rpms right at 3,000. Tonight I was driving 75 and had 3,000 rpms. This is after I poured in a bottle of Lucas trans fix. I did this because I started the truck and I could definitely hear something hitting something else. Not continuous, but rather like something metallic revolving and hitting against a stationary object. I thought my starter had fallen and the bendix was hitting the flexplate, but then i remembered i have a starter brace. And i verified it wasn't the starter. This weird and unbearable noise happened while the engine was running and the transmission was in park, it happened when i shifted into drive but slightly less frequently until i started to give it more throttle then it would grow in frequency and in pitch, so i shifted back into park and the sound went away until i stabbed the throttle, it really didnt like that.
So i shift back into drive because I'm about 2 miles from my dads house, as i start moving i find i can slightly give it throttle to get the truck moving without making the sound, if i give it to much throttle that metallic revolving sound is back again, so i give it more throttle to build momentum so i can relax my pedal effort. I make it to the local autozone grab the bottle of Lucas head right out and proceeded to get about half the 32 oz. Bottle into the transmission in about 20 minutes. Truck was not on at this time. I get in the truck turn it on, no weird sounds, idle is normal, shift into reverse no bad sounds, shift into drive and pull out of the parking lot and I mash the throttle, no bad sounds just really loud flowmasters
Truck seems "fixed" right? That's how this stuff in the bottle works isn't it?
I know it's not fixed. But I can convince myself of somethings if I try hard enough to ignore the facts. Lol.
So I go to my dads pour the rest of the bottle in the trans, add a quart of oil because it needs it, and I go for a mellow cruise around the neighborhood 25mph and less. Seems like the truck isnt responding to my acceleration NOR my braking efforts like it normally does. Idle seems slightly higher, shifting seems less engaging, i.e. smoother less noticeable shifting, less change of rpms between shifts. Drive the 30 miles back home which has that steep grade I mentioned earlier. And I have to admit there was a slight feeling i had of not being able to make it to the top. But luckily i did. I had the throttle at about 3/4 down to the floor while on the grade, normally this would put me at 75-80 while on the grade and not even questioning my trucks ability and not lugging down the engine. Tonight however the truck was doing barely 60 mph at the same throttle position while on the grade.

I made it home but the truck doesn't sound so well. No bad weird sounds since putting the Lucas in. Even after multiple starts and no wrench turning at all.

Now the sad sack story, this is my only vehicle. My daily driver, in addition to being practically flat broke, even though payday is Friday, and having a short paycheck, in addition to all of lifes hurdles that you and I all have. It still sucks to have happen to you. I was quoted by a local reputable shop $700 for a bench rebuild with torque converter and a shift kit installed. 2 day turnaround, remove and install myself.

Opinions?, comments?, smart-alike answers? I'm all ears. Thanks for reading. I feel better venting at least.
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Old 07-12-2018, 07:11 AM   #2
BRL
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Re: Th350 done for???

Quote:
Originally Posted by Mike_The_Grad View Post
Opinions?, comments?, smart-alike answers? I'm all ears. Thanks for reading. I feel better venting at least.
It's four in the morning here and I can't believe I just read your whole post.

...heck I even was able to avoid cris-crossing wrong lines somehow...amazing.

Glad you feel better for venting and I understand your frustration.

My Turbo-350 came out of a 1973 truck that someone had swapped it into, so no idea of its actual origin.

Then a semi pulled out in front of me, so I put it along with a V-8 into my '69.

Came complete with nasty brown fluid before I changed it, and yet all these years later it still shifts fine.

But it is getting tired, and I would really like to get a salvage yard spare to learn how to rebuild before mine goes south.

Of course that doesn't help your situation but I feel better now too.

Hope it works out for you.

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Old 07-12-2018, 08:22 AM   #3
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Re: Th350 done for???

First, you need to find and fix the reason you are putting in transmission fluid. It is bad for the trans to be low on fluid frequently.

I would check the vacuum modulator and it's vacuum hose.

Otherwise, it sounds like you have a bunch of other problems not related to the transmission.
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Old 07-12-2018, 10:23 AM   #4
Mike_The_Grad
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Re: Th350 done for???

I know it leaks from the detent cable seal. And I know it also leaks from the 1-2 accumulator cover.
I dont know if the trans is actually slipping as I've never been in a vehicle that had that problem. I do remember when I rebuilt the motor and put everything back together the truck didnt want to move under it's own power. I thought I had enough fluid in the trans, turned out I was almost a gallon low. But I filled it to the proper level and it ran fine. This was back in 2014.
There is a puddle of fluid under the transmission every day I walk out to the truck. When I park the truck on an incline with the nose uphill there isnt a single drop on the ground below the trans. If I park on an incline facing down hill it takes a while but there will be a small amount of fluid under the trans.
I just recently replaced the rubber 90 vacuum elbow that connects the transmission hard line to the vacuum modulator. And I know what it drives and sounds like if it were to fall off. It doesn't want to upshift. What I'm experiencing is not that. But heck I'll get another vacuum modulator and give that a shot. I would be much happier with a $13 repair vs. Having to rebuild it.
Thanks for the suggestion.
I do remember reading that the aftermarket adjustable modulators from some of the chain stores can be a crap shoot. And I think the modulator with a single red band that B&M makes is the preferred modulator to have.
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Old 07-12-2018, 10:45 AM   #5
jessemthompson
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Re: Th350 done for???

I would save up and take the shop up on their offer. It doesn’t sound like a bad deal. I’d also look into a good trans cooler while you have it out. Heat is the main killer of automatic transmissions.
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Old 07-12-2018, 10:58 AM   #6
Mike_The_Grad
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Re: Th350 done for???

I have a derale trans cooler. It's a 6 pass cooler mounted in front of the core support. It's the first thing to fresh air. And yes I've heard that heat is one of the biggest factors when it comes to automatics. Low fluid level being another.
Thanks for the suggestion. I was thinking that $700 wasn't to bad for a bench rebuild with shift kit and torque converter. I mean the things got 100k miles on it.
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Old 07-12-2018, 12:52 PM   #7
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Re: Th350 done for???

If the trans shop is doing good work, $700 is very fair.
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Old 07-12-2018, 07:57 PM   #8
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Re: Th350 done for???

You fluid loss is pretty significant, even for a leaking pump seal. Have you checked your coolant in the radiator? Reason I ask is that the radiator has a built in tranny cooler in the passenger side tank. If that tank leaks, your tranny will pump ATF into your coolant. The truck will continuously puke out the excess fluid as you drive, leaving room again for more ATF. This could also account for your engine temperature increase, as hot ATF mixed with coolant in your radiator does not help the cooling system. Just a thought. If your coolant is an odd reddish color, or brown, you may have a leak as described above. This could also mean you have some water in your tranny. A check of the tranny fluid in the pan would confirm this if it appears frothy.
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Old 07-12-2018, 09:36 PM   #9
Mike_The_Grad
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Re: Th350 done for???

I dont have the transmission cooler lines connected to the internal radiator's trans cooler. I only have an external Derale cooler doing the cooling of the trans. It's a 6 pass tube and fin type. I'm getting ready to replace the vacuum modulator with one I picked up at napa for $13. Also I'm going to check the intake manifold vacuum elbow that supplies vacuum to the modulator and replace the short rubber vacuum connector at the intake to the hard steel vacuum line. I vaguely remember similar symptoms when I found out the factory original modulator was bad. So I'm hoping that the modulator replacement is an end to the issues that im experiencing.
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Old 07-14-2018, 02:20 AM   #10
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Re: Th350 done for???

Well changing the transmission's vacuum modulator didnt make a difference in what I'm experiencing. I'm still going through the process of elimination in order to be absolutely sure if is the transmission. The simple solution would be to take it to the transmission shop and let them figure it out. Which I eventually will if I dont figure it out before then. Is it possible that an incorrect driveline angle in addition to a preloaded leaf spring rear suspension setup and lack of joint maintenance to cause loading of the transmissions output shaft transferring into loading the front pump and torque converter? What symptoms are associated with a broken front pump, torque converter or bad frictions inside the transmission?
My transmission still shifts. It does seem to be stacking the shifts though. If I'm leaving a stoplight with a gentle throttle, I'm shifting into second at 1400 rpms, then itll drop to about 1200 and at 1400 again it'll shift into 3rd. Same situation if I lay into it. Itll hold til almost 3000 rpms then shift into second and itll drop to about 2800 and then again at 3000 itll shift into third. It goes into reverse. It moves under it's own power. But theres this intermittant metal scratching sound that reacts to the throttle. Not instantly but it follows the rpms. It does this sound whether in park, neutral, or any gear. And it gets more frequent the more throttle I give it. As soon as I let off the throttle the noise stops until the rpms settle and I give it more throttle.
Maybe the one way clutch in the converter? The fluid is red, does not smell burnt, no noticeable particles on the stick or the rag after wiping. I'm going to pull the inspection cover and look at starter to flexplate engagement, flexplate integrity, transmission case vent valve for clogging. And fluid level.

I will figure it out and I will follow up with results. I'm mostly typing this out for notation. It's easier for me to type it out rather than right it down. Thank you to those that have replied. I appreciate it.
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Old 07-14-2018, 08:01 AM   #11
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Re: Th350 done for???

Well, I figured out whatsup with my truck....... good news and bad news....

Good news is: It's not my transmission that's causing what I'm experiencing.

Bad news is: It's my starter!

The bendix is sticking or what ever is responsible for disengaging the pinion from the flexplate. It will fully retract sometimes. But sometimes it won't and it will just sorta free float on the pinion shaft. So the rotating intermittant sound that seemed relative to engine RPM and also vehicle movement was in fact the bendix sliding back and forth on the pinion shaft and hitting the flexplate while it was running. My flexplate has some chewed up teeth on it. I really cant afford to replace the flexplate right now, financially or timewise. But I can replace the starter no problem because it has a life time warranty. 🙂
YES. I am running a starter brace, yes I do have knurled bolts that are the correct size and application for the setup I have. NO, I'm not sure this is the correct starter for my setup. But YES i do have the factory service manual to reference the correct starter motor that originally came in my truck. YES, i have tried a permanent magnet gear reduction starter, it worked awesome. But being that my flexplate is chewed up somewhat I didnt want to risk chewing up the bendix. So i sold it to my buddy who is doing a fresh build on his 71 SWB. He has a new flexplate and now a new mini starter and it works great on his truck. I will own another one and say goodbye to the old heavy ass starters of the past, but not until I'm able to afford a new flexplate. And bythat time I will actually be ready for a trans rebuild and maybe even an engine rebuild. Stroker motor FTW!!! 🙂

Thank you to all that have chimed in and even gave my issue the time of day to read my lengthy posts. I appreciate it. It's the reason why I decided to become a member and continue to utilize this great resource for our trucks.
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Old 07-14-2018, 12:33 PM   #12
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Re: Th350 done for???

leaky trans makes a junk trans quick.
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Old 07-14-2018, 12:55 PM   #13
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Re: Th350 done for???

Well, that’s cheaper than a trans rebuild! It’s also a quicker job. Just figure out your leaks while your down there.
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Old 07-15-2018, 03:07 AM   #14
Mike_The_Grad
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Re: Th350 done for???

The two major causes of the leaks on my trans is the Detent cable seal and the 1-2 accumulator cover seal. The detent leak only started recently when I decided to change the original detent cable to an aftermarket P.O.S. plastic one. It wasn't even leaking! I thought that after 45 years it was probably stretched and not getting the kickdown action it used to have. Plus the retaining mechanism at the top of the intake manifold that you adjust the detent cable was broken. So I put in a new detent cable and it has leaked ever since. It actually leaks a lot. And mainly while parked on flat level ground. It's really annoying.

The accumulator cover is probably because it's old. I mean the transmission has at least 100k miles on it, it also sat for 8 years installed in the truck and never ran or anything. I even had it sitting out of the truck wrapped in a trash bag for about a year while I was rebuilding the motor and reassembling the front end. I only had weekends to work on it.

So I replaced the starter in my truck. The bendix was bad on the one I took out. Lifetime warranty added up to $0 cost to me.🙂 I did buy 2 new starter bolts with the knurling on them. While I was under there I noticed that my block is cracked around the outer bolt hole that supports the starter. This is from when I reinstalled my old starter after trying a powermaster mini starter.(which is really awesome BTW. 7Lbs. Total weight, and cost me $110.) But being that my flexplate was a little chewed up I decided not to screw up the new mini starter bendix. And ended up selling it to a buddy. As i was reinstalling the old heavy H.T. starter i wasn't paying attention and over tightened the outer starter bolt causing it to break off in the block. I was able to extract it with a left twist drill bit rather easily. I checked for signs of cracking around the bolt hole but couldn't see anything obvious. I was mainly just happy to extract the bolt. Upon further inspection today however it is cracked alright. On two opposing sides. I'm assuming this is what's causing my starter to give me issues.
WITHOUT pulling the block and having it welded, what are my options?Obviously welding is the best and correct way to fix it but it's not feasible at the present time. What I did do was clean up the mounting surface real good, ran a thread chaser through both mounting holes, hit it with brake cleaner real good and sanded the paint off around the crack. I used some red threadlocker on the new starter bolts and snugged em up then waited about 3 or 4 minutes and lifted the rear of the starter to tighten up the starter brace in a supporting position, then torqued the 2 main bolts. I was thinking of spackling some JB weld on the outside of the block where its cracked.maybe to hold the bolts a little longer. I didnt want to jb weld the bolts in because well you know. But I do recall another post where a member used a long bolt threaded into the mounting hole from above and used like a mounting stud for the starter. He said it was the best setup for a starter he ever used. This being out of 7 different engines...

I did reconfigure my starter wiring too. I installed an American Autowire kit about 5 years ago. After checking the amateur terminals I made, I decided that they needed to be redone being as i have more knowledge and the correct tools now. Man, what a huge difference this made in the electrical system of the truck. My voltmeter used to show less than 13 volts while driving with my headlights on. Now it's just below 14 volts with them on! And the starter worked great. I went for a cruise and all is well in my little corner of paradise that I call my truck. 🙂
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Old 07-20-2018, 10:33 AM   #15
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Re: Th350 done for???

First off, great selection of parts for the motor. Should be torquey and more efficient than original.

The TH350 is smoked. Pull the dipstick and take a sniff. That akrid smell is burned oil mixed with clutch debris. It needed a reseal anyway...

Be sure to hook up your radiator cooler before your derale cooler. Temps kill and the factory cooler works great and even better with the external air to oil.
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