Fun With Transmissions - August - 2016

The 6F35N: Checking the Internals and Problem Spots to Watch

The 6F35N is standard equipment for a ton of small engine Ford products and they are starting to hit shops across the country. We have identified a few problem areas from the valve body, which we knew about a long time ago to the recently released updated center support (thanks Joey Campbell for the heads up).

Early on the 6F35n had valve wear issues. The main culprit is the solenoid regulator valve (figure 1). The wear on this valve will cause all kinds of crazy issues. Soft shifts, falling out of gear, radical bucking from take off are common symptoms of this issue. The easy fix for this problem is to replace the valve body. The updated valve body has more meat added to support the valve better (for a detailed explanation, refer to the August 2013 issue of gears magazine). As of this writing the valve body is available from your local Ford dealer part # CV6Z-7A100-B at a very reasonable cost.

Right from the factory this transmission has been plagued with drivers’ side axle seal leaks. The problem has been identified as not enough support from the axle bushing in the case. The bushing is too narrow to support the axle and allows it to sag into the seal causing a leak. Bob White and his crew at Superior Transmission Products designed a great fix for this issue. They designed a wider Teflon coated bushing that supports the axle much better and prevents the sag and fixes the leak (figure 2). They also designed a nice tool to remove and install the bushing and seal in the car (figure 3).

Center Support

Recently released is an updated center support. This support contains the low/reverse piston and the forward piston assemblies (figure 4). What is happening to the support is the Bellville spring retaining snap ring is popping out of the groove. When the snap ring comes out of the groove you may experience harsh 5-4 coast down shifts and harsh forward engagements. The updated support has a cupped washer under the snap ring to hold it into place.

Snap Rind Removal

Because the retaining snap ring in the center support is captured by the dished washer it takes a special tool to evenly compress the spring to remove the snap ring. I don’t care for buying a lot of special tools. I like to make most of my own special tools or figure out what will work with what I have around the shop. In figure 5 we see the ford special tool for this job. I took the support out into the shop and this is what I came up with: The sun gear shell out of a 4L60E is a perfect fit for this job (figure 6). Not only does it compress the spring evenly all the way around it has access windows to get to the snap ring (figure 7).

Front Pump

The front pump for this unit includes the Main Line Pressure Regulator and Tongue Converter Clutch Control Valves. These valves like so many valves these days need close inspection for wear. Also there are two blow off balls and springs in the pump. These can be checked by using a small amount of solvent and checking for leaks (figure 8). The pump gears may seem a bit sloppy in the pocket upon initial inspection. Most pumps, even new or low mileage, will have up to .006 in. clearance. This may seem like a lot but it is completely normal (figure 9). Lastly, be sure to align the notch in the pump bushing with drain back hole and do not drive the bushing too far into the pump or it will jam up against the shoulder of the body (figure 10).

The Stator Support

There are no sealing rings on the input shaft. The bushing in the stator support is what seals the converter charge/tcc release oil circuit so checking the bushing for wear is very critical. The problem here is the bushing is too deep for common calipers (figure 11). Bore gauges could be used and I am thinking most of us do not have those types of tools in our tool boxes. What we can do that is measurable and repeatable is use the “cellophane tape” method. Place a small piece, about 1/8 inch wide,(figure 12) of cellophane tape on the input shaft (cellophane tape is about .0015 in. thick). Now place the stator support down onto the shaft. If the shaft with the tape on it goes through the bushing the bushing has too much wear and must be replaced. If the bushing is in good shape the stator support will not go onto the shaft (figure 13).

There will be a ton of these units coming into your shops in the next few years. Knowing what to watch for and what needs updating will ensure a long-lasting unit and a satisfied customer. We all know that when we have satisfied customers we have more Fun With Transmissions!