The Stovebolt Site Forums The Shop Area Driveline 1958 automatic transmission reverse issue

hello

i have a 1958 short fleet with an automatic transmission, column shift.

lever full up = neutral
lever full down = reverse (should be?)

forward operation appears to be ok but reverse does not engage 75% of the time, sometimes with fussing i can get it to work.

is this something that might be a linkage adjustment?
when the lever is full down (which should be reverse)
the vehicle moves forward

i am still trying to learn the basics and that involves becoming acquainted with this particular type of transmission and its operation

thanks

A quick test of the linkage adjustment would be to engage the reverse shift position with the vehicle stopped, engine off. The driveshaft should lock. That's how Hydramatics have a "park" position. If the vehicle will roll in R with the engine stopped, adjust the linkage until there's a good "park" engagement. With the engine running a hydraulic lockout keeps the parking pawl from engaging.

Reverse is engaged by applying the front band and the rear cone clutch. Slippage of either one can result in poor or no performance in reverse. You need to perform two "stall" tests to determine if there's slippage.

1st. gear stall test: Engine running, brakes locked, shifter in "L" or "1" position- - - - -go to full throttle for a couple of seconds. The RPM should not go above 1900. If it does, adjust the bands.

If the 1st. gear stall test passes, move the shifter to R and kick the throttle open. A good 1st. gear test and >1900 RPM in R indicates a slipping cone clutch- - - -transmission overhaul time!
Jerry

BTW- - - -the 1-2 shift happens almost as soon as the vehicle starts rolling, so a slippy front band might not be obvious in normal driving without a stall test.
Jerry

Thanks
I will perform the tests you indicated
So am I understanding correct that if the truck will roll free when in reverse with motor off its a linkage issue?
If so is this linkage adjustment easy or complicated, I have never done anything like this before and usually have no help.

Assuming its not a linkage issue i would not invest the money in an overhaul, I would prefer to swap out the auto trans with a manual if its feasibly possible

Thanks

Yes, the driveshaft should lock in reverse with the engine off. Since "R" is the bottom of the quadrant, just adjust the linkage until the parking pawl engages and see how it affects the other quadrant positions. If there is an internal linkage problem with the reverse parking pawl that might not work.

Swapping to a manual transmission is a huge job, much more time-consuming and expensive than a Hydramatic overhaul, and butchering up an original Hydramatic truck that way should be a hanging offense!
Jerry

Thanks
Will the linkage/parking pawl adjustment be something mechanically obvious once i start polking around under the truck?

Concerning the swap to manual
Will the magnitude of the job be just as large if the donor transmission is from the same year/series truck?

There should be a threaded linkage adjustment to alter the length of the rod from the steering column to the transmission, and/or a sliding clamp at the shifter arm where the linkage attaches. The problem with a conversion involves the fact that there are different crossmembers, driveshaft lengths, carburetor, throttle linkage, bellhousing, starter, motor mounts, and even a different shape to the hole in the cab floor to allow access to the Hydramatic bellhousing. The whole truck got some pretty radical re-engineering to make the H-M work. The engine and trans were also mated together at the factory to assure proper alignment of the block, bellhousing, and transmission. If you do a swap, change the engine and transmission, and offer the entire Hydramatic engine, trans, and dedicated accessories for sale to someone who wants to keep their truck original.
Jerry

thanks Jerry, i spent some time today performing the tests you mentioned and also started exploring around under the truck
(prior to having the opportunity to read your reply)
my findings were exactly as you described, my particular setup was the "sliding clamp at the shifter arm " assembly.
i sprayed the clamp with some PB blaster and attempted adjustment, in the process (and this is embarrassing but i am still learning)
i discovered reverse is engaged by actually raising the shaft/shifter arm assembly via the "knuckle" type assembly at the base of the steering column. the good news is reverse does work, the bad news is the reverse "displacement" does not engage via the shifter arm, i have to physically pull the shifter shaft up while moving the shifter into the reverse position. any idea how to remedy that?
also the sliding clamp assembly was frozen up, i cleaned it with PB blaster and tightened it up well, its an odd setup, do these have a tendency to get loose over time?

i also noticed electronic wires/clips in the area, what role to these serve relevant to transmission/shifting operations?

thanks for the detailed explanation concerning conversion, i was under the impression a like donor truck would make things a bit easier. i guess i have more considerations to take into account.
my ultimate goal would be to have this truck setup reliably to take on the highway or a road-trip, i just dont know if that's feasible with the current original setup?

The wires are either for the backup lights or the "neutral safety switch" which is there to prevent starting in gear, probably both. The neutral switch will be at the top of the quadrant, and the reverse switch engages at the bottom.

A good cleanup and lube of the shifter should cure the problem with the mechanical lockout which is necessary to prevent getting reverse engaged while moving forward. Low range ("1-2" on the truck shifter IIRC) should be the last shift position available without lifting up on the shift handle to avoid getting into reverse accidentally. If there is wear or damage to the shift linkage involved, a post in the "parts wanted" forum of this site might get some results.

There is no good reason the truck won't be reliable on a road trip, at least as much as a standard shift vehicle 60 years old, as long as some basic maintenance is done first. Automatic transmissions are smarter than all drivers and most mechanics, as it's impossible to get one in the wrong gear. Most of them have safety circuits to prevent over-revving the engine, even when locked in Low range.
Jerry

The bracket with shift stops and the neutral start switch just clamps around the steering column. It may have just rotated slightly and be the cause of not being able to go all the way into reverse.