Hi,
I agree the first thing to check is the fluid condition and level. If that checks good, then we need to check line pressure. The idea that the vehicle won't go into reverse can be the result of low pressure. However, many years ago, there was a technical service bulletin regarding sticking valves in the transmission. Take a look through this:
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Here is the TSB I am referring to. The attached pic correlates with the TSB.
1978 Ford Truck Bronco V8-351 5.8L VIN H Windsor 2-bbl
A/T - Recurrent Sticking Valves/In Line Filters
Vehicle Transmission and Drivetrain Technical Service Bulletins A/T - Recurrent Sticking Valves/In Line Filters
A/T - RECURRENT STICKING VALVES/IN LINE FILTERS
TSB: 85-43
SUBJECT: VARIOUS UNITS
SITUATION: Recurrent sticking valves.
SOLUTION:
Possible solution - install in-line filters into transmission cooler lines (on return line between radiator cooler and the transmission.
Pic 1
Fluid returns to the upper cooler line on the following units: THM 350, THM 350C, THM 400, THM 325, THM 325 4L, Alum. PG, THM 125, THM 125C, and THM 700 R4.
Fluid returns to the lower cooler line on the following units: THM 200, THM 200 C, THM 200 4R.
Front & back fitting type units (such as the TF 727, TF 904, C-4, C-6, FMX, AT 540, etc.) Always return fluid to the rear cooler line fitting.
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With that, I would recommend taking both the return and supply lines from the cooler and make sure there is no restrictions. This could be causing the issue with low pressure.
Do this first and let me know if it helps.
Take care,
Joe
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Friday, April 17th, 2020 AT 7:11 PM
