News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

hydramatic transmission advice sought

Started by Jim Eccleston CLC 16079, December 22, 2005, 01:02:56 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Jim Eccleston CLC 16079

   I am soliciting your wisdom, experience, and advice concerning a growing problem with the transmission on BATILAC. I will describe the symptoms:
   This is on a 1961 Coupe de Ville, with hydramatic - all stock.
   Upon initial startup, I will shift into reverse to exit the garage. She runs and shifts perfectly. After a trip of more than a few miles, once the engine and transmission are warmed up, it is very difficult to get into reverse. If the trip is short, no problem. After my 5-mile drive to work, I can back into a parking spot. But much longer than that, or hotter, and there is a real struggle to get into reverse. It sounds as though something inside is rubbing. Imagine clutch bands that try to grip, but just cant. there must be some friction, since I can hear parts moving against each other - a groaning sound. It sounds almost like brake pads that rub against the drums - but this is definately coming from the transmission. Sometimes it will move in a jumpy fashion, a few feet, then lose power. I can rev the engine, all I get is more rubbing sounds. Sometimes the whole car shakes and rocks.
   If I park for a while, and let everything cool down, I can get reverse again. But after another drive, the same thing happens - Most of the time. Sometimes it does not do it. My reading of the shop manual indicates that maybe the reverse clutch is not getting enough pressure. Does reverse get more pressure that forward, and has to somehow overcome some other clutch that is also engaged? This is what seems to be happening - the battle of the clutch bands, and there is no clear winner.
   I first noticed this some time ago, and it came and went. But now it is getting fairly common, and I want to remedy it before it gets too bad.
   Advice, experience, or sympathy, anyone? What should I be looking at?

Doug Houston

You should be looking for someone who can rebuild your transmission, and who is honest and competent. The second two are the hard ones.

If you can hear sounds of things contacting or scraping, there is most assuredly a problem. On that transmission, the upshifts from 12- and 3-4 are hard to discern to begin with, and in some cases with failures, they arent there.

Dont be in a rush to find a shop to repair it. Its going to have to come out of the car, and its going to have to have a total overhaul. With most repair shops, theyve never seen one of these transmissions, and most of their employees were born after it went out of production. There are but two, or perhaps only one whom Id trust to go through my  own transmission. The last place to go is one of the franchised chains. It may be a long haul to find the guy who will get your transmission going properly again. Be careful of those who give you a number of a shop and tell you that theyre good, because they did a good job changing the fluid on a transmission.

There may be a good place in your area, but have good, airtight proof that the guy knows what hes doing, and that he will do it.

Jim Eccleston CLC 16079

   All of the shifts in forward gears are perfect, smooth, and silent. And it shifts in all 4 gears - of that i am positive.
   Fortunately, there is such a shop only a few miles away. Family owned, in business for 40 years, scrupulously honest. I take all my automotive work there. I have an appointment to take it in Wednesday, but I want to be able to give them as many clues as possible.
   Again, the only problem is in reverse, when hot.

Thanks for the help!!!

Ed Mobley - CLC 19300

Jim,

Search on my prior posts and youll get an idea of what I went through with my 60 Caddy.

The fact the problem gets worse when hot leads me to believe you have a pressure problem.  It could be a worn pump or bad internal leak.  But the sounds you describe....well that could be anything.  In my case, the transmission output shaft bearing had come apart and it made terrible scuffing noises.  

Drop the pan...check the valve bodies.  Are they loose?  Are there metal filings in the pan?  

I rebuild these transmissions to monetize my hobby, but I prefer to work with people in N. California so I can do face to face business.  Where are you located?

Whatever you do, make sure the shop has the proper tools.  One critical tool is the Unit End Play Gauge Kent Moore 6282F.  This is critical when chosing the proper selective washer especially if any hard parts have to be replaced.

Regards,

Ed

Mike #19861


 Im going to shine in here with my limited automatic transmission expertise.

 Reverse generally has a higher pressure than the forward gears, primarily for the higher gear ratio compared to 1st forward. If the seals that activate the reverse clutches, or bands, are worn, they will be more prone to leakage. This problem will worsen as the transmission gets hot, the fluid thins and internal tolerances increase.

 That would explain why this only happens when the transmission is hot, and only in reverse.

 Mike

Ed Mobley - CLC 19300

Correct...when the tranny is put in reverse full pump pressure is applied to the reverse piston (should be around 160 to 200 PSI at half throttle).  If that pressure cannot be achieved, either there is a bad leak or worn pump.  Forward gears should read about 90 PSI.

As per the service manual, you can hook up an oil pressure gauge to the 1/8 fitting on the reverse piston housing (at the bottom rear of the tranny right next to the pan).  I did this when troubleshooting my tranny and it was very helpful (it helped me recognize a severe leak in the front coupling unit due to an oil ring in the rebuild kit that was too small).

Regards,

Ed