Introducing the 6-Speed 6F35 Transmission
solenoids which are a Bosch design and known to be fairly reliable. The engineers really put some
thought into simplifying the job of troubleshooting this valve body. In this design, there’s one solenoid and one regulator valve that control each of the four shifting clutches. Keep in mind that each shift is accomplished by releas- ing one clutch and applying another. The one shift that isn’t a clutch-to-clutch shift is the downshift from 2nd to 1st, because the low sprag is holding. In diagnosing a transmis-
sion for general slips, flares or bangs, you’ll probably be dealing with an overall pres- sure or computer strategy problem. If you’re dealing with a shift problem that only affects one clutch, all you need to focus on is one sole- noid, one regulator valve, or one clutch. There is an exception to
this: A compensator piston is mounted inside the clutch housing on the 3-5-reverse and 4-5-6 clutch pistons (figure 5). The compensator is there to assist the return springs of both clutches dur- ing release. So if the compen- sator piston or circuit fails, the transmission might develop a slower or faster clutch action during some situations. There’s one on-off shift
solenoid. Its job is to apply the low-reverse clutch and block the TCC apply circuit. So if lockup comes on in low or reverse and kills the motor, the problem is most likely a crossleak in the pump, a stuck TCC control valve, or a restricted cooler. Hydraulically, we see
potential for problems in the pump assembly and valve body. Any wear in the pump pocket will have a big effect on pressure, due to the small size of the pump gears. And the pressure regulator valve doesn’t have a wear sleeve, so any wear in this bore will
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require an oversized valve or a new pump assembly. At the moment it’s hard to predict
which bushings or hard parts are going to be weak links inside this unit. I’d expect the pump assembly to cause pressure and lockup problems. As for the valve body, look for worn Actuator Feed Limit (AFL) and
compensator valves. I’d also suspect both the 2-6 clutch regulator and 3-5-R clutch regulator valves to wear, since each valve has to stoke eight times shifting up to sixth gear and then back down to first (figure 6). During a rebuild, watch out for
the Teflon seal at the back of the stator shaft. If it’s cut or nicked, you could have a converter circuit leak.
Use extra care with
the Belleville spring and snap ring for the 2-6 clutch at the bottom of the case. Someone could easily damage the snap ring seat and ruin the case.
But in general, it
looks like a fairly easy transmission to deal with: So until football season starts up again, don’t be afraid to tackle a 6F35.
Figure 4
Clutch Housing Including
Compensator Piston
Figure 5
GEARS May/June 2010
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