727 with fmvb question

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DOMINANTmopar

DOMINANTmopar

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Hi all.

I have a 727 with a forward manual valve body (fmvb) and b&m shifter. Two times now driving home from work the car started heating up in traffic. I then lost my 2-3 and 3-2 shift. Everything was working fine on the way to work and around town. The fluid level is slightly over full and is red. No offensive smell either. Anyone have any places to look first or what the problem could be.

Thanks
 
Do you run an external cooler? That might help. I installed one in my car along with a trans temp gauge.
 
I do have a trans cooler and no trans temp gauge. It is run in front of the radiator and the trans fluid only runs through it and is not hooked In Series with the radiator.
 
What exactly do you mean by "lost" 2-3 and 3-2?
You could shift it but it made no difference?
 
How big is your cooler? Unless it's a pretty good size cooler it may not be enough by itself. You have to remember you need air movement across it for it to cool and in traffic you probably didn't have much air movement. Stop and go traffic with just an aux. cooler can overheat a trans. pretty fast. Being over full (even if it's not a lot) can also cause fluid aeration.

And as TB said please explain "Lost 2-3 and 3-2"? Are you saying 1st and 2nd worked fine, just no 3rd gear?
 
DOMINANTmopar said:
Yes. My 1-2 shift was fine. I did not have 3rd.
Click to expand...

Did 3rd come back after it cooled down?

What do you think about this Tracy?
Fluid too hot and thin for it to apply because of leakage past valves and sealing rings?
 
Ok so the first time this happened I did get 3rd gear back after the car was cool. I drove 125 miles that day just to see if the problem would come back. I had no problems, but I never got caught in traffic.

My plan of attack for this weekend is to get the fluid level correct (it was above the full line....and yes I checked it in neutral) and to run my trans cooler in series with my radiator. Does that sound reasonable?

Last month I put in a new trans filter, new fluid and a 3000 stall converter. I did not see any debris in the pan and the fluid was clean. The filter was also in good shape, but I put a new one in anyway.

If I was getting frothing happening wouldn't the problem show up sooner and also affect my 1-2 shift?

Oh one more thing I should mention. Before I lost 3rd gear I did start to get soft shifts to third. They were delayed if you will. I would stay on the gas, shift into 3rd and a second to a couple seconds later the trans finally decided to shift into 3rd. A couple times also I let off the gas after I shifted to 3rd and then it finally shifted. Weird.

thanks guys for the replies. I really want to get to the bottom of this issue.
 
Yes, run your cooler in conjunction with the rad cooler. Into the rad cooler out to the external and return to trans.

You also didn't mention the converter in the OP, what is it, off the shelf, custom made? You could be experiencing a lot of slippage if it's an off the shelf converter and therefore generating heat. I would seriously consider installing a trans temp gauge as well.
 
Yes it is a custom made converter. Sorry I forgot to mention it earlier. I normally don't get any slippage especially when I am heavy on the throttle. The car usually runs very well.

I like the idea of having a trans temp gauge. I will look into it.

I will make the changes and drive around this weekend. I will report back on my findings.

thanks
 
As far as affecting the 1-2 shift it's hard to say because the two gears(2nd and 3rd) use different abounts of fluid to apply the gear.
Might have gotten clear fluid on the 1-2 and then hot foam on the 2-3.
 
Yes I agree with you trailbeast. I talked to another one of my mopar buddies who said to fix the trans fluid level first. He pretty much said the same thing you just did.
 
Is it possible that your trans is OVERfilled and is foaming?
 
I thought I solved the problem with the fluid levels. I drove to work again and the problem came back. I talked to a guy I know that owns a trans shop and he said it could be a cracked piston in the high clutch drum. That is all foreign to me, so what do you guys think?

I am thinking of dropping the trans and bringing it to the shop.
 
I'd be surprised a cracked piston in the high clutch drum could even function at all, but I have seen some odd things so I guess its possible because a cracked piston would undoubtedly leak.

If it were me, here's the order I'd do things

Drop the pan and make sure the valve body bolts are all torqued down properly (100 inch lbs). If any are loose you probably found the problem.

If none are loose I'd drop the valve body and do some air pressure tests, especially the front clutch circuit. If you want a chart on what passages do what I can post it. You apply 30-40 psi to each port and listen for them to engage and listen for any leakage.

Have you ever put it in reverse after it's hot and lost 3rd gear? If it's a front clutch issue you shouldn't have reverse either because it's one of the components that give you reverse.

How many miles on this transmission?
 
Not sure on the mileage. I was told by the previous owner that it was rebuilt recently. That can mean anything. Thanks for the suggestions. I will drop the trans as soon as I can and take a look. Great info. Its a weird issue to me. I always have reverse. I just lose third after about 20 miles.
 
I had a friend who had the same issue with a GM T400. Turned out to be a hairline crack in the case. Not saying that this is your issue, just saying that these things can happen.
 
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