727 problems, opinions wanted...

[jimmyray]

I have a 73 340 Duster with a 408 stroker and a 727. The 727 has a high stall convertor (3000 rpm TCI streetfighter) and a manual reverse valvebody.

Symtoms:
1. When I first start the car, and place it into reverse, it will take several seconds and some high revs (maybe 2500) to get it to begin to move backwards. When I shift it into first, the same issue. However, once it gets moving past ~15 mph or so, the problem disappears. If I start the car for less than 1 hour, and restart it, the problem does not repeat. However, engine off for a couple hours, and the problem returns.

2. I have a fluid leak coming from the front of the tranny - maybe the front seal, maybe...?

3. Symptom #1 above is gradually getting worse - longer warm up, higher revs to first get it moving.

4. Car will move slightly if I put it in nuetral and rev the engine. This may not be related to 1 or 2 above, but it is odd.

Any suggestions?


NOTE: The pics below were take during the rebuild. Both engine and tranny have unknown miles on them. The tranny face was dirty, so I cleaned it up a great deal. I inspected the front seal, and it looked to be in new shape, so I did not replace it. I was concerned I would damage somethiong if I tried to remove and replace it. I did not have the correct tools.

 

[70Duster440]

Funny, I had a front pump seal leak with a new tranny and TCI converter.

What you described sounds like a drain back problem where the converter drains back into the tranny when it sits and has to refill when you put it in gear. Now, with a bad pump seal, you've got a serious drain-back, or I should say, drain out problem.

Always a good idea to replace the pump seal when you have the tranny out, despite how good it may look.

With it out, you may want to go one step further now. Drain the transmission and pull the front pump. Buy a new pump seal, o-ring, gasket, sealing washers for the bolts, and a pump bushing. You can call a place like Transmission Exchange and get everything for less than $10.

Take the front pump apart and take the pump housing, your seal, and bushing to a trans shop and have them install the parts. It'll take them 5 minutes and they probably won't charge you anything.

Put the new o-ring on the pump and reinstall it with the gasket. Lube everything up with vaseline and it'll go back together easily.

The new bushing will assure that the converter isn't wobbling and wiping out the seal. Everything else will cover most everything else that can leak from the front.

Re-adjust the bands and button it back up. You shouldn't have movement in neutral. If the problem persists you may have a valve body problem - or worse. In the end, you may be better off tearing the whole thing down for an inspection.

 

[Aaron]

It almost sounds like your in between gears.

 

[GЯEENHOЯNET]

are you sure its not coming outta the vent?

 

[bOb shingler]

i'd say the low/reverse servo piston lip seal needs replaced. you also need to apply some grease to the vertor neck when installing it into the trans.

 

[340jeff]

a 727 or 904s will only prim the converter in neutral or in gear small converters tend drain back while sitting. try putting it neutral for just a moment when you first start it. thats why you must check the fluid in neutral on all rear wheel drive mopars

 

[SGBARRACUDA]

Over the years of building 727's which along time ago i worked a a shop that did all the mech. work for Hillsborough Co Fl. Sherrifs Dept. This was a common sign in 727's. I found it to be piston seal leak by on hardened seals. When we would rebuild these trans. the problem would go away. Since you have movement in neutral, I would think the shift selector valve is out of position.

 

[340sFastback]

are you sure its not coming outta the vent?

I have to run my trans a pint low in order to prevent it from spitting fluid out of the vent. Now the front of the trans is bone dry.

 

[jimmyray]

are you sure its not coming outta the vent?

In the pic below, is the vent located at #5? Perhaps small converter drainback, coupled with a full pan, could cause it to be coming from the vent.

FWIW, the movement in nuetral is only when I rev the engine. There is a noticeable difference from 1st to neutral, RPM's go up slightly, etc. But when I rev it, it move slightly, but not like it is in gear.

 

[70Duster440]

While converter drainback is common, in your case based on your description, it is severe. I think you have a more serious problem going on.

Yes, #5 is the vent.

And below is right out of the FSM.

 

[mullinax95]

I had a 68 Charger with a 727 and a 2800 stall Mopar converter. It would take some revs to get the car to move in reverse after sitting over night. I drove it for years with it doing this. Putting it in neutral would help it build up and it wouldn't rev up to start to move.

I would do what 70duster440 said and go from there.

 

[fishy68]

The guys are correct about it being a classic case of torque converter drain back which torqueflites are famous for. Also correct is the part about putting it in neutral for a few seconds before you put it in drive to fill the converter.

Wanting to pull when in neutral could be a product of the last person that rebuilt it set the rear clutch pack tolerances a little too tight. Or it could be a valve body problem. The only way to tell for sure is to check the pressure going to the clutch pack when in neutral. If it has any pressure it's a valve body problem. If it don't have pressure it's a clutch pack problem.

I would also recommend what Duster440 said and pull the pump out for inspection of the bushing and replace it if needed and replace all the pump seals. The only thing I can add to this is if when you pull the pump out the clutch packs will also want to fall out because the front pump is basically what holds them in place. If you tighten the front band adjuster down snug before you pull the pump out it'll hold the clutch packs in place so installation of the pump will be much easier. Just don't forget to readjust the front band after your done.

 

[jimmyray]

You men are a WEALTH of knowledge - I love this site!

Since the tranny is in the car, and less than convenient to remove, I am going to try the following:

Lower fluid volume by 1 pint.
Warm car in nuetral to fill convertor.
Hope this eliminates the leak and the high rev/slow move problem
Ignore the nuetral move issue.

I should have posted for tranny recommendations before I reinstalled the motor. Shoulda-woulda-coulda fixed any pump problems soooooo easily.

If this aint it, I will be forced to pull the tranny or take it to a shop (ughh). Seems the "pro's" at the shops often know little more than I do, and care a whole lot less. Hate to have my car messed up while it is being repaired! (scratch this, forgot to reconnect that, broke the other, etc.)