I have a 1966 Lincoln Continental Convertible that I am the 3rd Owner with low mileage that I had a major restoration done about 2 1/2 years ago. I’ve recently started having some problems with the automatic transmission delayed shifting into first gear after stopping at a red light or stop sign. In order to get the car moving, I have to accelerate very very gently at an incredibly slow rate until first gear engages and gets up to about 5-7 mph, and then it accelerates and drives well until I get up to about 40 to 45 MPH and then there is a “shuddering” sensation that causes the vehicle to bounce up and down until I get to about 55, and then it seems to run fine again. The issue is particularly pronounced if I am starting from any sort of uphill grade (which frequently causes the engine to die) or am driving up a steep hill, and I seem to have a reduction in power.
I’ve already had the suspension checked and it is fine, so I’m thinking the “bouncing” may be resolved by having the wheels balanced and aligned, but wanted to see if you had an opinion as to whether it was related to the transmission issue.
I’ve owned the car for about 8 years now, and the problem seems to be getting increasingly worse. Any suggestions as to the cause or things to look at to help more specifically diagnose the problem? Thanks!
The transmission problem that you are describing in my opinion does not seem to be related to the shuddering and bouncing at the higher speeds. A personal road test may however prove otherwise. A transmission that is low on fluid can behave this way. If the oil in the transmission is correct as per the dipstick, the unit may require a reseal internally and may even lead to a complete overhaul. A good transmission shop that is familiar with these c6 transmissions should be able to road test the car and give you an honest opinion.
The vibrating and shuddering issues can be caused by several separate and common problems. The age and balance of the tires as well as the drive shaft condition are very important. Old tires can start to decompose, crack and cause all sorts of unwanted vibrations as well as be certainly unsafe to use. I would have them evaluated and if safe have them rebalanced. The drive shaft on your 66 Lincoln has what is known as Double Cardan U-Joints. This is an excellent system that uses two u-joints with a center yoke between them at each end of the drive shaft. The u-joints and the yokes can and do fail. The yokes have a provision for grease to be added to their bearings but many have never been greased. The transmission end of the drive shaft has three special bearings that are inserted into the splines and these must not be miss-handled or lost. I would advise you to have the drive shaft inspected by a mechanic who is competent and knowledgeable with these types of units. Finally, some Lincoln convertibles and even some sedans of this era can be fraught with structural shakes and vibrations if any of the body and under hood braces or brackets that were installed at the factory are removed. They were engineered to provide structural integrity. Convertibles were particularly sensitive in this area and in fact the 66 convertible even had a special tuning weight installed behind each front wheel behind the metal splash shield.
The above suggestions should be done with the easiest first and the car should be road tested after a definite fault is found and corrected before proceeding to the next item. Unibody vehicles that are severely corroded may be a special challenge. Let us know what you find.