Newbie Mopar Owner - Fury III Automatic Transmission Slipping?

[Blue_66_Fury]

Hello all!

I'm looking forward to utilizing this thread as much as possible. Up until now I have never owned any mopar cars, or even any classic cars. I am more or less self taught when it comes to doing mechanics, with only a couple years of wrenching experience in tech school (I'm 24 with no prior car experience before entering tech school), so please bear with me as I do my best to describe certain issues I'm experiencing with my 66 Fury III.

I bought this car with the intention of not having a project, as the previous owner had presented a lot of work done to it already. The first few weeks of ownership were great, the car drove good and I didn't experience any issues. Until recently, I noticed that when I'm cruising down the road at any speed above 30mph, the car will bog down. When the car is cold, it drives fine and I can accelerate fairly quickly without experiencing performance problems.

When the car has warmed up, and I'm cruising down at above 30mph (usually around 55 is my average speed) the car will slow itself down. My foot on the gas pedal doesn't move, from the way the car sounds it's as if it wants to downshift. You can hear it slowing down (thanks to the loud exhaust). It's not putting itself into neutral, as there is some response in acceleration when I give the gas pedal light pressure.

When this happens, it feels like something is holding the car back, sometimes it will lurch in and out of this weird state. Not a violent lurch or knocking feeling, imagine constantly pumping the gas softly, it's that sort of lurch. If I completely lift off my foot from the gas pedal, and let the car slow down for a while (let's say from 55 to about 40), and resume giving it gas, it will go back to being bogged down right away and I can't accelerate past 30mph (when the car gets to about 30, that's when I can somewhat accelerate again before it bogs back down to 30ish). I sometimes have to pull the car over, let it sit for a bit in park, then it can get back up to faster cruising speeds for a little bit before bogging back down.

I tried coasting in neutral when this happens, and shifting back into drive. This sometimes works, but then it bogs right down. If I continue to hold the gas pedal down with this happens, the car will slow itself down to crawling speeds.

This has to be a transmission slip right? I've never really worked on transmissions before, so I don't even know what slipping feels like. I've been reading through some old books and this forum, and it sounds like it might have something to do with kickdown? I hope I was able to explain it good enough, and I hope there is someone out there who is willing to offer some advice! I'd love to have this car ready to drive for the cool fall weather

Thank you all for taking the time to read this, and I appreciate any advice given!

 

[Davea Lux]

Start by checking the transmission oil level. Put the car in neutral with the park brake on and a wheel chock in place. Start the car and check the oil level for the transmission. It should read full with the car running. Note the condition of the oil, is it clear? Does the oil look dark and/or does it smell bad (burnt). If the oil is in good condition, the transmission is probably not failing. Has anyone messed with the kick down adjustment? (That is the rod that runs from the carb down to the transmission) Erratic performance can also be the result of transmission bands that need to be adjusted, as you a a novice, you probably should have a transmission shop adjust the bands and check the kick down adjustment. Or as an alternative, download the FSM for free at www.mymopar.com. The FSM gives detailed instructions on how to adjust the bands and the kick down adjustment. The band adjustment should be done before changes are attempted on the kick down adjustment. It is also possible the the transmission filter is clogged which can also cause performance issues. The filters usually do not get clogged until the clutches and bands in the transmission are failing. In that case you are headed for a transmission rebuild. An engine that is misfiring will also cause transmission issues with shifting as rough running messes up the torque curve for the engine and for lack of a better explanation confuses the transmission as to when to shift.

Dave

 

[413]

What is the engine rpm doing when car slows down with foot steady?
Going up?
Going down with the car speed?

 

[Just Carbs]

Do you have the ability to install a fuel pressure gauge just before the carb that can be seen in the car?

 

[1970FuryConv]

You have not proved that you have a transmission issue.
At his point, you really need a friend who knows something about old cars.
Limited fuel going to the carb can cause the problem
Since the car is fine when cold, but has limitations when going over 30 mph with engine hot, it the fuel line getting hot? Is the fuel going into vapor lock? Is the fuel line too close to an exhaust manifold?
Again, getting a friend who knows about old cars to help you look might provide a simple solution to what seems to be a big problem.
Welcome, persevere and you will get your Mopar running right.

 

[CBODY67]

Doesn't sound like a transmission problem to me. If they operate fine when cold, as long as the fluid is at the correct level, they operate fine when warmed, or vice-versa.

I suspect the "lurching" might otherwise be a "lean surge", which is most likely a fuel supply issue. If NONE of the service receipts you received (or were told about) included NEW RUBBER FUEL LINES, tank to carb, then look at those first. They normally get old, but E10 fuels clean the oils out of the rubber internally, first, and then progress to the outside, which can mean fuel leaks and air intrusion into the rubber lines via cracks and such. Do note the special clamp on the fuel line at the tank, as it also serves as the ground for the fuel gauge.

Then check the tune-up specs. Timing light and dwell-tach needed for this. Invest in some decent ones as they can be used in the future, too. Which can also need a few different screwdrivers, too.

If you have not a lot of tools, I'd have recommended you head over to Sears-Roebuck and get a basic Craftsman socket and wrench set, but as the current "Craftsman" tools are not what they originally were, other sources might be needed. Plus a few straight extensions and a u-joint.

When were the spark plugs last changed? Plug wires?

Is the choke flap on the carb opening as it should, as the engine warms up? Might be that the choke is staying closed and not opening, resulting in a too-rich mixture as the engine gets to operating temp, which can also result in a softer version of "surge".

Given the recent track record of new ignition condensers, that can cause lots of drivability issues on points ignition systems. Finding a good used one is usually better than a completely new one.

If the engine is a 361/383/413/426-Wedge/440, it could also well be a worn fuel pump pushrod.

If you have not already done so, head over to www.mymopar.com and do a free download of the Factory Service Manual. Then read through it to familiarize yourself with the car and its various mechanical systems. Also, you can also download a Factory Parts Manual, which has exploded views of components.

You can also plan to watch some of the Chrysler MasterTech videos on various subjects. This way, you can get the same "factory training" that dealership techs got back then.

Enjoy the learning experiences!
CBODY67

 

[Blue_66_Fury]

Start by checking the transmission oil level. Put the car in neutral with the park brake on and a wheel chock in place. Start the car and check the oil level for the transmission. It should read full with the car running. Note the condition of the oil, is it clear? Does the oil look dark and/or does it smell bad (burnt). If the oil is in good condition, the transmission is probably not failing. Has anyone messed with the kick down adjustment? (That is the rod that runs from the carb down to the transmission) Erratic performance can also be the result of transmission bands that need to be adjusted, as you a a novice, you probably should have a transmission shop adjust the bands and check the kick down adjustment. Or as an alternative, download the FSM for free at www.mymopar.com. The FSM gives detailed instructions on how to adjust the bands and the kick down adjustment. The band adjustment should be done before changes are attempted on the kick down adjustment. It is also possible the the transmission filter is clogged which can also cause performance issues. The filters usually do not get clogged until the clutches and bands in the transmission are failing. In that case you are headed for a transmission rebuild. An engine that is misfiring will also cause transmission issues with shifting as rough running messes up the torque curve for the engine and for lack of a better explanation confuses the transmission as to when to shift.

Dave

Hi Dave,

I checked the transmission oil after doing a quick test drive to warm things up. It looks very good and clear. I have not found it in my notes that anyone has messed with the kick down adjustment. I have ordered a service manual from eBay, as I don't know whether or not mymopar is a safe website to download from. Speaking of misfiring, the engine does run fairly rough at start up, I'm going to check the plugs and other ignition components (the tune-up was done before I had purchased the vehicle, and the paperwork states the tune-up was done last fall and they had replaced just about everything)

 

[Blue_66_Fury]

What is the engine rpm doing when car slows down with foot steady?
Going up?
Going down with the car speed?

Hi 413,

The engine rpm will slowly go down with the car speed, it never has gone up (which I'd imagine is a good thing?)

 

[Blue_66_Fury]

You have not proved that you have a transmission issue.
At his point, you really need a friend who knows something about old cars.
Limited fuel going to the carb can cause the problem
Since the car is fine when cold, but has limitations when going over 30 mph with engine hot, it the fuel line getting hot? Is the fuel going into vapor lock? Is the fuel line too close to an exhaust manifold?
Again, getting a friend who knows about old cars to help you look might provide a simple solution to what seems to be a big problem.
Welcome, persevere and you will get your Mopar running right.

Hi 1970FuryConv,

Yes, I really do need a friend who knows something about old cars hahaha. The fuel line is warm to the touch, never too hot to handle. And it sits nowhere near the exhaust manifold.

 

[Blue_66_Fury]

Doesn't sound like a transmission problem to me. If they operate fine when cold, as long as the fluid is at the correct level, they operate fine when warmed, or vice-versa.

I suspect the "lurching" might otherwise be a "lean surge", which is most likely a fuel supply issue. If NONE of the service receipts you received (or were told about) included NEW RUBBER FUEL LINES, tank to carb, then look at those first. They normally get old, but E10 fuels clean the oils out of the rubber internally, first, and then progress to the outside, which can mean fuel leaks and air intrusion into the rubber lines via cracks and such. Do note the special clamp on the fuel line at the tank, as it also serves as the ground for the fuel gauge.

Then check the tune-up specs. Timing light and dwell-tach needed for this. Invest in some decent ones as they can be used in the future, too. Which can also need a few different screwdrivers, too.

If you have not a lot of tools, I'd have recommended you head over to Sears-Roebuck and get a basic Craftsman socket and wrench set, but as the current "Craftsman" tools are not what they originally were, other sources might be needed. Plus a few straight extensions and a u-joint.

When were the spark plugs last changed? Plug wires?

Is the choke flap on the carb opening as it should, as the engine warms up? Might be that the choke is staying closed and not opening, resulting in a too-rich mixture as the engine gets to operating temp, which can also result in a softer version of "surge".

Given the recent track record of new ignition condensers, that can cause lots of drivability issues on points ignition systems. Finding a good used one is usually better than a completely new one.

If the engine is a 361/383/413/426-Wedge/440, it could also well be a worn fuel pump pushrod.

If you have not already done so, head over to www.mymopar.com and do a free download of the Factory Service Manual. Then read through it to familiarize yourself with the car and its various mechanical systems. Also, you can also download a Factory Parts Manual, which has exploded views of components.

You can also plan to watch some of the Chrysler MasterTech videos on various subjects. This way, you can get the same "factory training" that dealership techs got back then.

Enjoy the learning experiences!
CBODY67

Hi CBODY67,

All of the rubber lines have been replaced, and the ignition tune up was performed in the fall of last year. I've also placed an order for a good quality timing light with tach and well capabilities built in.

The choke appears to function as it should, opens up slowly as the car warms up. Today on my test drive, the surging happened a bit quicker than the last time. It is also much hotter out which could be the cause.

The engine is a 318, and the paperwork states that a new fuel pump was installed, so I'd imagine the pump pushrod would have been replaced with it as well?

I'll make sure to check out Chrystler MasterTech videos on youtube!

 

[Just Carbs]

Does the fuel filter after the pump have small return line to the tank?

 

[Blue_66_Fury]

Does the fuel filter after the pump have small return line to the tank?

Hi Just Carbs, no it does not have a return line going back to the tank

 

[Davea Lux]

Hi CBODY67,

All of the rubber lines have been replaced, and the ignition tune up was performed in the fall of last year. I've also placed an order for a good quality timing light with tach and well capabilities built in.

The choke appears to function as it should, opens up slowly as the car warms up. Today on my test drive, the surging happened a bit quicker than the last time. It is also much hotter out which could be the cause.

The engine is a 318, and the paperwork states that a new fuel pump was installed, so I'd imagine the pump pushrod would have been replaced with it as well?

I'll make sure to check out Chrystler MasterTech videos on youtube!

Mopar small blocks do not use a push rod, so that is not an issue. ight want to remove the fuel filter to check it for water, rust etc.

Dave

 

[Big_John]

I don't know whether or not mymopar is a safe website to download from

It is safe. I've downloaded a lot of their manuals with zero problems. All get checked by my software as they download and I use Adobe Acrobat to read them and, as I understand it, that software will also find viruses in the PDF download.

 

[413]

What is the engine rpm doing when car slows down with foot steady?
Going up?
Going down with the car speed?

Hi 413,

The engine rpm will slowly go down with the car speed, it never has gone up (which I'd imagine is a good thing?)

If the trans is slipping the rpm will go up as you stay steady on the throttle.

 

[Blue_66_Fury]

Hello everyone,

I want to let all of you know that I do believe we figured out the issue! 1970FuryConv was correct, it was a simple solution to fixing what seemed like a major problem. After doing some closer observation, I noticed that (someone before me had installed a see-thru secondary fuel filter between the pump and the carburetor) the fuel level inside that secondary filter was very low. I took off the main filter before the pump and noticed right away how there was a bunch of nasty brown sludge that poured out of the inlet side.
So I got myself a new filter and wouldn't you know, the flow of fuel was much better and I could see that gas filled up the entire bowl of the secondary filter. Thinking back on it, a fuel delivery issue does make a lot more sense than a transmission issue. Faster speeds demand a higher rate of gasoline, and the clogged lines couldn't keep up with the speeds I was going at.

I want to thank you all for helping me through this dilemma, I truly appreciate all of your advice. I was able to cruise at a solid 55mph and not experience any bogging down. I was also able to WOT from a stop with no issues either! Before the day ends, I will perform one more test drive to make sure the issue was indeed fuel related.

Thanks again all!

 

[live4theking]

If there was that much crud in the filter you may want to change the metal fuel lines or blow them out with compressed air, from back to front.

I'd replace that filter again in a month or so too.

 

[Just Carbs]

Plan on changing a lot of filters.
The filter before the pump was probably put there to protect the pump from a rusty gas tank. The clear one was to monitor and see what's going on.

 

[CBODY67]

I concur, the pre-filter, on the supply side of the pump is to do just what it was doing . . . keeping the rusty stuff out of the pump. The post-pump filter is normal location, I suspect.

During the winter, plan on either taking the existing tank off for cleaning and sealing or get a new tank for installation. You can make a decision on replacing the fuel lines, at that time. Until then, keep an eye on that pre-pump filter and change when necessary.

CBODY67