1988 bronco ii locked up in reverse


Chuckc

Member
Joined
Aug 21, 2019
Messages
33
Reaction score
2
Points
8
Location
Florida
Vehicle Year
1988
Make / Model
Bronco ii
Transmission
Automatic
thanks well put!
No, not really, you could use a C3 or C5 automatic from a 2.8l engine, same bolt pattern as 2.9l, but they are 3-speeds no OD, and your computer would turn on CEL(check engine light) full time because A4LD solenoids are no longer connected.

Manual trans swap is a whole lot of work, with new pedals and steering column

A4LD may just need the valve body rebuilt which can be done without removing transmission
First thing would be to drain the fluid and inspect the fluid and pan for metal bits
If metal bits are found then transmission needs to come out, you have mechanical issues not just "pressure" issues

All automatics run on fluid(ATF) pressure, forward requires 125psi, reverse 175psi, this is why reverse is usually effected first if there is a pressure issue, like in your case.

In the front of the transmission is the Main pump(front pump, and only pump, lol)
It is connected to the outside case of the torque converter, so spins at engine RPMs, increasing engine RPMs increases pump RPMs so it pumps more fluid
This fluid is sent to the Valve body where its restricted flow thru the passages builds up the pressure
Inside the valve body are "valves", lol, of course, hence its name, valve body
These valves route the fluid, under pressure, to the clutches and bands(brakes) in the transmissions main body, the rotating part of transmission
The clutches engage and disengage the internal shafts
The bands hold the disengaged shafts from spinning
This is how "gears"/ratios are selected

In the bad old days the valves were all operated by springs holding them closed, or open, until enough pressure built up and started to push them open, or closed, engine vacuum or a cable was also used for downshifting, over riding a valve's spring
In the mid-1980's automatics started to get solenoids instead of springs to operate the valves, the engine computer would operate the solenoid/valves based on RPMs, speed and engine load
Way better for shifting but an added complication as some saw it, lol, they still prefer carbs, to each his own

But what hasn't changed are LEAKS inside the valve body, in the bad old days and the good old days, gaskets and o-rings on the valves will start to leak over time and that causes lower pressure in the valve body, and that causes slipping and lack of certain "gears", like reverse

So rebuilding the valve body with new gaskets and seals can solve many issues, it's not a final solution for sure, clutches and bands do wear out, like brakes do on the wheels, and the main pump can get weak
But rebuilding the valve body needs to be done regardless when a transmission is rebuilt, so even if it doesn't solve the problem totally its not wasted money, or time, since its done, you just need to replace bands and clutches along with pump to do full rebuild
thanks well put!! I should add that it’s not just reverse also looks like just overdrive is working... no drive #1 or #2.. I guess I’ll remove body of valves and go from their.
 


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