TH350c Slipping

Turbo4whl · Apr 1, 2022

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How can one fluid be good for 4 types of Mercon, 3 types of Dexron and whatever Dodge and all the imports use?

Asking for a friend.

Dex Merc, wrecking more transmissions every day.

scenic760 · Apr 1, 2022

Matt69olds said:
Most shift kit plates are yellow anodized, TransGo plates are black. Stock plates are natural steel with no coating

Hmmm...it was a natural steel plate...however I can 100% guarantee someone other than the factory was in there before I was as there were aftermarket gaskets..

I was looking on the Transgo website and their shiftkit mentioned something about keeping the 350c separator plate and drilling it out instead of replacing it...maybe some shade tree shift kit?

I feel like Quincy, MD (yeah, I'm old! Haha) trying to forensically recreate what may have happened but this truck spent it's life on a ranch since 1999 (last year registered) and the owner passed away so I have zero history...

It wouldn't surprise me if it slipped before I got to it and it just was never addressed..maybe the rebuild had 350 gaskets instead of 350c?

I actually saved all the old stuff I took out.. I was pretty damn careful putting it back together but I'm not a master builder!

scenic760 · Apr 1, 2022

Turbo4whl said:
You must be registered for see images attach

How can one fluid be good for 4 types of Mercon, 3 types of Dexron and whatever Dodge and all the imports use?

Asking for a friend.

Dex Merc, wrecking more transmissions every day.

I have wondered the same thing!

Along with that train of thought, whatever they were using 40 years ago for adhesives and friction materials are probably completely different from what is being used today? So modern parts=modern fluids ...?

All that being said, I'm assuming there are still flow rates that these things were probably designed with that may get thrown for a loop with the wrong blood type pumping through the veins..was just thinking this stuff was the O neg of the transmission world?

SirRobyn0 · Apr 1, 2022

Turbo4whl said:
You must be registered for see images attach

How can one fluid be good for 4 types of Mercon, 3 types of Dexron and whatever Dodge and all the imports use?

Asking for a friend.

Dex Merc, wrecking more transmissions every day.

I'm hardly a tranny expert, but I've been around in the repair industry for a good long time and tend to geek out a bit on fluids, any how I would like to share my thoughts.
You're question: "How can one fluid be good for 4 types of Mercon, 3 types of Dexron and whatever Dodge and all the imports use?"
The short version. It's not.

Read on for the long version of what I think / have put together though the years.

So back about 15 years ago I worked for Goodyear. Goodyear was always looking for a way to save a buck even if it cost more in the long run. They had us on this program from a while where we pumped DEX III into EVERYTHING, plus a bottle of additive, so if it was a Chrysler product we put the ATF+4 additive in it. It was one of my first experiences with a fluid (additive) that was one size fits all. It was horrible. The onslaught of customer complaints about shifting, just in the store I ran, was almost enough to get me to quit. I don't think they were even on that program for a year.

At the shop I currently manage I have an entire double shelf that has nothing but the factory filled ATF fluid for most of the vehicles we commonly see.

DEXIII is still made, under various specs. ACDelco still makes the stuff, they call it type III (H) which was the last release or specification of DEXIII you can bet that's what's in my tranny and what's on the shelf at the shop. Is there better fluid for our trannys, maybe, like I said I'm hardly a tranny expert, but it's the closest thing you're going to get to what went in our trucks at the factory in todays world. Now some guys will say that something like the Valvoline maxlife is better because it's full synthetic and will prolong the life of the transmission and lower temps and take more heat before breaking down. That may very well be true and when the day comes I rebuild my transmission I may go to something like that. But lets be clear, that fluid is a modern fluid spec'ed for Dextron VI / Mercron LV, it considered improved over previous releases of dextron so it's "backward compatible". Oh and Valvoline still makes DEXIII, in the blue bottle simply called DEXIII.

scenic760 · Apr 1, 2022

Very insightful Rob! I honestly didn't even think they still produced Dextron III!

I met Andy Rooney (60 minutes) one time and I brought him a hat from the company I was working for. He examined it front and back, which I assumed he was looking for a snap back or something and then I said "It's a one size fits all!" I'll always remember how quickly he responded (because he was old when I met him) and said "You know what they say about one size fits all don't you? That means it doesn't fit anyone."

scenic760 · Apr 1, 2022

I have been reading a few articles here and there and looking at the gaskets I took out, it looks like they were from a shift kit? I was also reading a few instruction books from different shift kits and it looks like for the 350c, you would use the exiting plate and drill out some holes? If so, it would also stand to reason the separator plate was either modified or replaced before I got in there? If all that holds true, it would probably mean that whatever gaskets that came with my rebuild kit were not compatible with what was already in there, much less the dual feed mod I did internally?

I'm pretty sure that is at least ONE problem, if not THE problem? Given all of that, should I try to find a stock 350c plate and gasket set (which is harder than it sounds!) and install or do you think there is an after market plate/gasket set I could use with the internal dual feed mod?

THANKS AGAIN!

SirRobyn0 · Apr 1, 2022

scenic760 said:
Very insightful Rob! I honestly didn't even think they still produced Dextron III!

I met Andy Rooney (60 minutes) one time and I brought him a hat from the company I was working for. He examined it front and back, which I assumed he was looking for a snap back or something and then I said "It's a one size fits all!" I'll always remember how quickly he responded (because he was old when I met him) and said "You know what they say about one size fits all don't you? That means it doesn't fit anyone."

I don't know all the details but there is something about the licensing and they can't actually say Dextron III anymore on the bottles. So the ACDelco stuff is GM TYPE III, and other companies shorten it to DEXIII. IDK all the details on licensing.

Turbo4whl · Apr 1, 2022

scenic760 said:
Hmmm...it was a natural steel plate...however I can 100% guarantee someone other than the factory was in there before I was as there were aftermarket gaskets..

I was looking on the Transgo website and their shiftkit mentioned something about keeping the 350c separator plate and drilling it out instead of replacing it...maybe some shade tree shift kit?

I feel like Quincy, MD (yeah, I'm old! Haha) trying to forensically recreate what may have happened but this truck spent it's life on a ranch since 1999 (last year registered) and the owner passed away so I have zero history...

It wouldn't surprise me if it slipped before I got to it and it just was never addressed..maybe the rebuild had 350 gaskets instead of 350c?

I actually saved all the old stuff I took out.. I was pretty damn careful putting it back together but I'm not a master builder!

You are right about the early Transgo shift kit. Drilling out a couple separator plate ports, moving a check ball got rid of the shift lag (overlap) between gears. GM designed the trans for mom and pop America. The Transgo kit would bang the gears and chirp the tires on the 1-2 shift and the 2-3 shift. Of course this was tough on the rest of the trans parts.

scenic760 said:
I have wondered the same thing!

Along with that train of thought, whatever they were using 40 years ago for adhesives and friction materials are probably completely different from what is being used today? So modern parts=modern fluids ...?

All that being said, I'm assuming there are still flow rates that these things were probably designed with that may get thrown for a loop with the wrong blood type pumping through the veins..was just thinking this stuff was the O neg of the transmission world?

You could be right about newer rebuild kits using friction material that would be okay with different friction modifiers. All I know with my many years servicing vehicles, factory built transmissions do not respond or perform well when the wrong fluid is used.

Octane · Apr 2, 2022

SirRobyn0 said:
I'm hardly a tranny expert, but I've been around in the repair industry for a good long time and tend to geek out a bit on fluids, any how I would like to share my thoughts.
You're question: "How can one fluid be good for 4 types of Mercon, 3 types of Dexron and whatever Dodge and all the imports use?"
The short version. It's not.

Read on for the long version of what I think / have put together though the years.

So back about 15 years ago I worked for Goodyear. Goodyear was always looking for a way to save a buck even if it cost more in the long run. They had us on this program from a while where we pumped DEX III into EVERYTHING, plus a bottle of additive, so if it was a Chrysler product we put the ATF+4 additive in it. It was one of my first experiences with a fluid (additive) that was one size fits all. It was horrible. The onslaught of customer complaints about shifting, just in the store I ran, was almost enough to get me to quit. I don't think they were even on that program for a year.

At the shop I currently manage I have an entire double shelf that has nothing but the factory filled ATF fluid for most of the vehicles we commonly see.

DEXIII is still made, under various specs. ACDelco still makes the stuff, they call it type III (H) which was the last release or specification of DEXIII you can bet that's what's in my tranny and what's on the shelf at the shop. Is there better fluid for our trannys, maybe, like I said I'm hardly a tranny expert, but it's the closest thing you're going to get to what went in our trucks at the factory in todays world. Now some guys will say that something like the Valvoline maxlife is better because it's full synthetic and will prolong the life of the transmission and lower temps and take more heat before breaking down. That may very well be true and when the day comes I rebuild my transmission I may go to something like that. But lets be clear, that fluid is a modern fluid spec'ed for Dextron VI / Mercron LV, it considered improved over previous releases of dextron so it's "backward compatible". Oh and Valvoline still makes DEXIII, in the blue bottle simply called DEXIII.

I've been told dexronVI is compatible with dex 3.But it is a lower viscosity fluid and we won't run VI in a dex 3 tranny. Mopar branded fluids in the 50s and/ or 60s was rebranded dexron.And Chrysler had some sealed transmissions that had lifetime fluid,like they also claim today with their 8spd Z trannys.The theory was if the tranny was as sealed as possible,was never opened up to oxygen then the fluid wouldnt oxidize and need changing. Imo...bs on that.

SirRobyn0 · Apr 2, 2022

Turbo4whl said:
You could be right about newer rebuild kits using friction material that would be okay with different friction modifiers. All I know with my many years servicing vehicles, factory built transmissions do not respond or perform well when the wrong fluid is used.

I agree with that for sure.

Octane said:
I've been told dexronVI is compatible with dex 3.But it is a lower viscosity fluid and we won't run VI in a dex 3 tranny. Mopar branded fluids in the 50s and/ or 60s was rebranded dexron.And Chrysler had some sealed transmissions that had lifetime fluid,like they also claim today with their 8spd Z trannys.The theory was if the tranny was as sealed as possible,was never opened up to oxygen then the fluid wouldnt oxidize and need changing. Imo...bs on that.

Yea, the other thing if you geek out on Dextron III fluid, there were a number of different releases. For example Dextron III (G) was a synthetic blend, and as far as I know is completely unavailable today. Dextron III (H) which is what the ACDelco GM type III (H) fluid is, is a oil base group 2 which is a conventional. Dextron VI is synthetic, and I do not like the idea of pouring a synthetic fluid in my high mileage trans. Would I do it on fresh rebuild? Possibly? I mean we all know there are benefits to synthetics vs conventional. I do tow a fair bit. I'm all about extending the life of components, but I've had GM trannys use in trucks, with coolers and gauges, serviced regularly still around at well over 200K. I had one Chrysler tranny at one point over 400K on ATF+3, which was also conventional base stock. So given that I'd probably run old fashion Dextron III, keep it cool and service it as I always have. I'd probably be more comfortable with that.

There are a number of new build lifetime fill auto trannys and transfer cases today. They all seem to have level check and top of ports of some kind so at the shop we recommend those be serviced by sucking out the fluid and refilling with the factory fill fluid. No fluid is lifetime, that's just a way for manufactures to claim lower maintenance costs IMO.

Octane · Apr 2, 2022

I remember back in the 1970s that there was antifreeze that was called permanent.I remember radiators that were corroded and often had to be replaced on almost every car I came into contact with.I cannot see any fluid,oil that could possibly be truly permanent. The factory is hoping the vehicle will just outlast the oil and the oils failure wont be blamed maybe.

scenic760 · Apr 5, 2022

I haven't had time to troubleshoot the trans for a while but was looking at ordering a new plate/gaskets just to make sure I had the right ones. I did pull out the parts I had left over from the rebuild kit and there were 2 new gaskets for what I'm assuming is a non lockup th350 so that leads me to believe I did at least put the right ones in!

I was trying to wrap my head around how the th350 works and I decided to try disconnecting the modulator... I'm not sure if it means anything or not but I was getting the same exact behavior with the vacuum modulator disconnected as well?

scenic760 · Apr 14, 2022

Hey All,

So I have a used th350 that was operating before it was pulled..Once again not the most experienced guy with a wrench, but I was getting everything ready to swap it (change filter) and I tried to spin the stator shaft and it doesn't spin...I looked at a couple of other threads and it seems as though the stator shaft does NOT spin?

If I remember correctly when I installed the one in there now the stator shaft spun but was really stiff...from a couple things I have read it seems that a moving stator would give me exactly what I'm experience right now?

1. Changes in torque converter stall speed and operation

2. Extreme heat generation in transmission and torque converter

3. Failure of transmission clutches, bands, and overall performance issues

Matt69olds · Apr 15, 2022

The stator support tube (the larger tube with the splines closest to the transmission) is pressed into the pump, and should not turn. The stator support tube holds sprag stationary in the converter, if the sprag is free to turn all the time, you have no torque multiplication.

If the stator tube is loose, the pump is junk. The tube is splines and pressed int the pump, damage to either means both are junk.

scenic760 · Apr 16, 2022

Matt69olds said:
The stator support tube (the larger tube with the splines closest to the transmission) is pressed into the pump, and should not turn. The stator support tube holds sprag stationary in the converter, if the sprag is free to turn all the time, you have no torque multiplication.

If the stator tube is loose, the pump is junk. The tube is splines and pressed int the pump, damage to either means both are junk.

Ahhhh.....that makes a lot of sense!
I should hopefully be able to switch the transmissions out after spring break and get to the bottom of it!

TH350c Slipping

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