727 Loud shuddering bang/clunk noise under load going up hill *UPDATE*

[Evan Frucht]

Sort of sounds like a hard 2-3 trailing throttle shift due to poor timing of the band/clutches but the part about going up a hill kind of throws me off as that usually means you are feeding it some throttle. Checking for a loose torque converter mount bolt, or cracked flex plate and worn transmission mount are good, cheap first steps.

I'm hesitant to really stomp on the throttle because I'm still feeling the car out and don't want to damage anything. I may not be giving it enough gas?

is it possible that I'm just overloading/stressing the trans (or pushing it to hard,) and that's the sound it's making because it doesn't want to be shifting 1-2-3 in "drive" when going up that hill, and it wants to be in "first" instead.

What is a hard shift supposed to sound/feel like?
could what I'm experiencing be considered normal and the reason its so loud and overwhelming is because the car doesn't have any carpet/ headliner/ or middle rear seat (9 pass wagon) and there are a few holes in the floor.

could you explain in more detail what a "hard 2-3 trailing throttle shift" is and why the fact that its going up a hill makes you skeptical of that?

thanks !

 

[Evan Frucht]

Almost sounds like the differential. The trans evidently shifts fine from what you say. Suppose your gear is not a sure grip. Reckon you checked the underside making sure everything is tight since it's described the car was apart. Raise rear wheels and check for any run out. Ah...just how steep is that hill?

forgive me for being unexperienced, but how do I check for run out, or rather, what is "run out"

I also noticed when installing my new drive shaft, that the rear end has play in it--- or maybe that's not the best way to describe it.... more specifically, the yoke could be twisted back and forth a before it engaged the rear end.

I have no idea if that's normal or not and couldn't find an answer in the manual!

if the way I described the rear end play it is hard to understand I can try to explain better.

 

[493 Mike]

I think it may help to have a copilot with you for diagnoses.
Mike

 

[Don Frelier]

And from what I gather the rear end is suspect

 

[Evan Frucht]

I think it may help to have a copilot with you for diagnoses.
Mike

Would be nice!

No expert here, trying to learn more. My strong suit is definitely body work but I like to try to do as much as I can myself. I know a thing or two about working on cars, and drive a 1967 bug daily. But that has a peppy little 4 speed manual which has never given me trouble in the 50,000+ miles I've drove it since I bought it. Mopars are new to me and so are automatic trans in general. My dad used to own a 1965 Plymouth Fury Vert with 383/727 combo years ago, but he kind of avoided doing extensive repairs himself on that vehicle, and ended up letting it sit until he sold it I think because he didn't want to deal with its issues anymore, even though I think they were pretty minor. He regrets selling it of course... He has driven my car with me and he has no idea but says "something doesn't feel right."

Anyone one who knows old mopars is welcome to come drive it and take a look.​

 

[Evan Frucht]

And from what I gather the rear end is suspect

The only thing that makes me think the rear end is fine is because I dont hear the whining, howling sound everyone talks about with rear ends going bad. The loud bang only happens for a moment then its gone. What would cause a rear end to make a loud single "bang" when under load, but be quiet the rest of the time its operating?

 

[Hemi 354]

Does this car have a shift kit installed in the transmission?

 

[Evan Frucht]

***UPDATE***

A Few days ago and all the other times I've driven it was shifting from 1-2-3- and R and kicking down. Now its not working right altogether. Just drove the car with my father. He seems to think that the transmission is slipping all over the place. Didn't even get to a point where it made the loud bang. Now its barely even working and not making enough power. Only got the point where it shifted from 1st to 2nd but was very mushy then we turned around. Now it barely even wants to go into drive. Now I'm starting to think it has always struggled a little to move, even though the engine is running strong. It's hard to diagnose because I have not driven this car much, and have never driven it (or even another car very similar) in perfect working condition. Been doing a lot of little things to it but have only tried to drive it maybe 7-8 times total.

That's a bummer.

Any ideas or is this grounds for a full transmission overhaul?

I will probably need to find a good transmission shop who knows 727s well and have the car towed to see if they can try to drive it and do some tests.

 

[Evan Frucht]

Does this car have a shift kit installed in the transmission?

I have no idea what the original owner did. He told me he had it rebuilt 5 years ago

 

[khryslerkid]

I'm thinking by reading one of your post that you changed the trans fluid. You had stated that you drained the torque converter. If you changed the filter, did you make sure it was a two hole filter?

(From allpar.com)

"There are a few different in-pan filters that will physically fit, but on a pre-1966 transmission, you need a filter with two fluid ports in it. The 1966-and-up filter has only one, and if you use it on a 1965 or earlier transmission, you’ll starve the rear pump and damage it; you’ll wonder for a few days what that weird siren-type noise is that increases in pitch with road speed—that’s the rear pump operating with insufficient oil.

A 1964-1965 transmission filter (with two ports). The NAPA or ATP № 19715 or 17956 filter/gasket kit contains the two-port filter. Others include Wix № 58656 and Fram № FT-1015A."

 

[Evan Frucht]

I'm thinking by reading one of your post that you changed the trans fluid. You had stated that you drained the torque converter. If you changed the filter, did you make sure it was a two hole filter?

(From allpar.com)

"There are a few different in-pan filters that will physically fit, but on a pre-1966 transmission, you need a filter with two fluid ports in it. The 1966-and-up filter has only one, and if you use it on a 1965 or earlier transmission, you’ll starve the rear pump and damage it; you’ll wonder for a few days what that weird siren-type noise is that increases in pitch with road speed—that’s the rear pump operating with insufficient oil.
View attachment 713657A 1964-1965 transmission filter (with two ports). The NAPA or ATP № 19715 or 17956 filter/gasket kit contains the two-port filter. Others include Wix № 58656 and Fram № FT-1015A."

When I changed the fluid I re-used the same filter that was on it, It didn't look clogged so I sprayed it with brake cleaner and blew it out with the airgun and it cleaned up well. I do remember seeing that it had two holes, I remember thinking "what are those for." I'm pretty sure I put it back on correctly as well.

 

[khryslerkid]

When I changed the fluid I re-used the same filter that was on it, It didn't look clogged so I sprayed it with brake cleaner and blew it out with the airgun and it cleaned up well. I do remember seeing that it had two holes, I remember thinking "what are those for." I'm pretty sure I put it back on correctly as well.

How much crud was in the bottom of the pan?

 

[matthon]

Wasn't your poly changed from a 2 to 4 barrel?
I believe there is a specific kick down rod for a 4 barrel, and maybe the bracket as well. I think the 2 barrel one can be modified, not sure.
Just a thought.

Also, isn't there a converter seal that can go bad causing the fluid to drain out of it completely. If the kickdown seal is bad it'll be noticable because it will drain right out of the trans after shutting the engine off.

 

[khryslerkid]

Matthon touched on what I was going to ask about the kick down linkage being properly adjusted. If it doesn't apply some pressure it can cause damage.

 

[Evan Frucht]

Matthon touched on what I was going to ask about the kick down linkage being properly adjusted. If it doesn't apply some pressure it can cause damage.

The kickdown is adjusted properly as far as I know. The car had the 4 barrel when I bought it, I think the PO had it put on. It had a modified 2 barrel kickdown rod. Early on I had noticed the kickdown lever on the trans wasn't going fully back (it was going most of the way tho.) So I made further adjustments to the rod and got it so it would go fully back when the throttle was floored.

 

[Evan Frucht]

How much crud was in the bottom of the pan?

1 quarter sized smudge and 1 dime sized smudge. looked like what I guessed was clutch material, kind of metallic looking but not metal fragments or anything.

Also, how long does the converter take to refill itself? after its drained and once new fluid is added

 

[khryslerkid]

Evan I admire your persistence and wanting to figure this out. It's great to see the younger generation taking on these dinosaurs.

Your statement about your dad going along and his comments, plus it sounds like it's slipping now, makes me think it's time for a rebuild.

 

[khryslerkid]

The converter shouldn't take long to fill at all. Fyi, you check the fluid level only in neutral.

Did the pan have a fresh gasket, looked like it hadn't been too long since someone else had been in there? It might have been having problems before you bought it and someone was looking for a quick fix?

 

[Evan Frucht]

The converter shouldn't take long to fill at all. Fyi, you check the fluid level only in neutral.

Did the pan have a fresh gasket, looked like it hadn't been too long since someone else had been in there? It might have been having problems before you bought it and someone was looking for a quick fix?

Pan gasket, It did look pretty fresh. Also glued to pan with a thick smear job of silicon. They really cream cheesed it on so to speak.

The park cable housing I also had some trouble with and actually got a good used one thanks to a member here (my old was broken and was basically glued in placed with silicone.) I actually started a thread on that a while back.

 

[Evan Frucht]

Evan I admire your persistence and wanting to figure this out. It's great to see the younger generation taking on these dinosaurs.

Your statement about your dad going along and his comments, plus it sounds like it's slipping now, makes me think it's time for a rebuild.

I think you are right. It's been hard for me to accurately asses and describe the issues the car is having with the transmission because frankly this car is somewhat of a basket case and have done a bunch a different work to it at different times in between the occasional short test drives in my neighborhood. I don't think its too far from being a good reliable driver though. Maybe a quick and painless Transmission rebuild is all it needs. Possibly even be the time to spice it up a little (shift kit) too match my dual exhaust, 4 barrel, and suspected cam work.

Again I have basically zero experience driving an old V8 like this, and don't have any gauge on how powerful it should feel. I drive a light little 4 beater with 4 speed (67 vw) everyday its the only car I've ever owned before this, my first. I've also only driven a hand full of automatic cars in my life, none of which were mine, and none were this old. That being said I've always felt like this one should feel quicker.

Come to think of it, from the beginning its felt like the car was struggling a little to move itself, and not because of the engine. And that I was just sort of being wishful a few times. It definitely has shifted somewhat normally a few times. I'm just sort of spitting stuff out here, its really hard to say given my lack of experience driving these cars.

At this point I know the engine is good, carb rebuilt, new plugs, wires, points etc
Finally got the shifter mechanism working properly a week or so ago
I know my drive shaft is good. Just had a new one made.
I know my motor mounts are good
I think my rear end is ok but really have no idea

I've probably spent about $100 so far on ATF. Once filled after park pawl housing replaced. Then I drained it completely more recently to put a new pan on it and added new fluid again. Ha!

I definitely need another person to at least try to drive it on flat ground because I'm lost on this one, and my dad has no idea.

I think I need to find a good trans guy that is local to me and have him rebuild it if that's what it needs. I have enough other work I want to do... just want it to drive good for now. So it can be a "running and driving project." I don't really want to just have a car sitting around while I try to learn how to rebuild a transmission. don't have enough time for that atm