Trans problem, need advice

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B'cuda

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I have a 69 340 A727 with a full manual reverse valve body. The converter is 340 high stall. The cam is the old Direct Connection 474/280?
The problem is after the trans gets hot, it slips on take off and hardly has reverse. In both cases, alittle rpm and it drops into gear. It pulls great and the 1-2 shift is solid, chirps the tires, the 2-3 shift is instant with no lag. I run a separate stacked plate tranny cooler with fan.
My first thought is bands or trans but could it be the converter?
If it is the bands, is there a way to tighten them to get anything?
Any advice will be appreciated
 
I have a 69 340 A727 with a full manual reverse valve body. The converter is 340 high stall. The cam is the old Direct Connection 474/280?
The problem is after the trans gets hot, it slips on take off and hardly has reverse. In both cases, alittle rpm and it drops into gear. It pulls great and the 1-2 shift is solid, chirps the tires, the 2-3 shift is instant with no lag. I run a separate stacked plate tranny cooler with fan.
My first thought is bands or trans but could it be the converter?
If it is the bands, is there a way to tighten them to get anything?
Any advice will be appreciated

Rev and it drops in gear is almost always the clutch pack piston seals.
Fluid is leaking past them and hot fluid being thinner leaks past them quicker, making it slip when hot.
It's possible it's something else, but usually that's the symptom of worn rubber seals.
A plugged up filter could also do it.
It isn't the converter.
 
Yeah, the kick down is long gone, I will drop the pan and change the filter. I bought a rebuilt trans still in a crate but would like to hold off until after this season to put it in if I can, have alot of things ahead of that job.
Thanks for the input!
 
Back in the day I heard of mopar guys running Ford ATF, claiming that it swelled the seals. Anyone have any suggestions on what fluid may help?
 
Type F grabs the clutches a little harder. Old guys have told me a little brake fluid works for swelling the seals.
 
Back in the day I heard of mopar guys running Ford ATF, claiming that it swelled the seals. Anyone have any suggestions on what fluid may help?

As mentioned F type fluid has a little more grab on the clutches.
This is due to F type being a bit less slippery on the clutch materials, and I use F fluid in my 42RH trans for this reason.

There are a couple of things you can try for a temporary solution until you are ready for the new trans.
Transmission stop leak products, because they swell the rubber in the clutches just like they swell seals to stop leaks.
Another believe it or not, is to replace 1 quart of the trans fluid with 30wt motor oil.
This thickens your fluid a little helping it seal better (like when the fluid is cold) it leaks by less and will not hurt your trans at all even if it doesn't help.

In your case you called it slipping, but it is probably actually a non engagement until the pump pressure rises enough to apply clutches.
An actual slip burns the hell of things, and a non engagement doesn't so much.
It just doesn't engage the clutches until the fluid volume is enough to do it. (usually)
I'd bet once your trans is in gear it acts fine, and this is the clue that it's not actually slipping.

Here's a bit of information you might find interesting.
Back when a section of law enforcement in the US was looking for vehicles from US manufacturers they wanted a vehicle that could use the same lubricant in as many places as possible.
Mopar showed that motor oil could be used in the TF transmissions instead of ATF.
Not only does motor oil lubricate better than ATF, it's thicker and so leaks by sealing rings and clutch pack lip seals less.
This could actually help your lazy engagement problem until you are ready for the new trans.
 
I have a 69 340 A727 with a full manual reverse valve body. The converter is 340 high stall. The cam is the old Direct Connection 474/280?
The problem is after the trans gets hot, it slips on take off and hardly has reverse. In both cases, alittle rpm and it drops into gear. It pulls great and the 1-2 shift is solid, chirps the tires, the 2-3 shift is instant with no lag. I run a separate stacked plate tranny cooler with fan.
My first thought is bands or trans but could it be the converter?
If it is the bands, is there a way to tighten them to get anything?
Any advice will be appreciated


Need one of these. they are all for sale.

20200426_163321.jpg


20200426_134555.jpg
 
Lip seals on a tf are usually go or no-go. Fords have grommet type seals that can be inconsistent with heat and cold, but tf seals are good til they blow and completely lose pressure. I never put sealer in a tf. Lots of times in Fords and it does work many times.
 
Type F grabs the clutches a little harder. Old guys have told me a little brake fluid works for swelling the seals.
When I was going to high school I worked part time at a gypo used car lot. Any oil leaks anywhere here was the solution. Get the steam jenny going to get it clean, add some brake fluid, and voila..NO MORE OIL LEAKS. Would work for short period of time.
 
The tip off tho is no reverse.

In reverse all pressure regulation is bypassed so whatener the pump puts out is what you get, usually over 275psi.
In reverse the hi-drum is engaged and the L/R band, and nothing else.
In manual low; the Forward clutch is engaged and..... you guessed it the L/R band.
So the only thing those two have in common is the L/R band. Tighten her up and see what happens.
 
Thanks for all the replies, I thought hard about not calling it a slip, because it will drop into gear with a gentle rev. What made me think it's a slip is that when the idle is set up high it will roll forward when I let off the brake. Then when I give it gas it seems to be in neutral for a second, then grabs. But the reverse is almost not there (hot). Everything is great when it's cold.
I'm going to drop the pan, filter and tighten the low/reverse band.
I have an old Chiltons book and an inch pounds torque wrench. The procedure calls for 47-50 inch lbs. if an adaptor is used (before backing off 2 turns). I'm sure I will need an adaptor, anyone know what I'll need? Thanks again.
 
Lip seals on a tf are usually go or no-go. Fords have grommet type seals that can be inconsistent with heat and cold, but tf seals are good til they blow and completely lose pressure. I never put sealer in a tf. Lots of times in Fords and it does work many times.

I have to disagree with TF tranmissions being go or no go.
That's where the phrase "Morning sickness" comes from relating to TF's, is when the seals are old and cold so they don't flare out to the bore until they warm up enough.
 
Probably 90% of all automatics have the same type of lip seals as tfs..but we don't hear about th350s or 400s having morning sickness. Sounds like low fluid level to me.
 
I have to disagree with TF tranmissions being go or no go.
That's where the phrase "Morning sickness" comes from relating to TF's, is when the seals are old and cold so they don't flare out to the bore until they warm up enough.
I always thought morning sickness was referring to converter drain back when the vehicle sits and the fact that ft do not fill the converter in park.
 
The Park and Neutral circuits are the same except in Park, the manual valve dumps fluid. This reduces the line pressure from something like 55psi, to half or less. The lube circuit, is still active, as is the TC charge circuit. But at idle, not enough oil flows into the TC because the manual valve is dumping most of it into the pan.
However, the 69 FSM shows a TC check valve, which is supposed to prevent TC drainback. I mean I guess cuz why else would it be there,lol.
 
I always thought morning sickness was referring to converter drain back when the vehicle sits and the fact that ft do not fill the converter in park.

Converter drain back could be called Morning Sickness I guess, but actually that term is used when the rubber seals inside the clutch packs gets old and hardens up so they don't flare out and seal to the piston bores until the fluid gets warmed up enough to soften the seals so they can flare again and seal.

This can in some more extreme cases take quite awhile, unlike converter drain back being resolved in a few seconds.
 
Update: I dumped the fluid and changed the filter. I tightened the low reverse band and backed off 1/4"+. Filled it with Ford type F fluid.
I got the chance to roadtest it and problems seem to be solved. I'll know for sure tomorrow.
The old fluid was clean but there was some band material in the pan, not to much. But for now, its backing up with purpose and leaving with authority!
Thanks for the replies and advice to this thread!
 
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