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I have a rebuilt 235 engine with the original trans in 54 pick up. When on the freeway it slips out of third gear when i start to go over 55mph. Anybody have this problem also..

fairly common condition for the old 3 speeds, mostly due to worn syncros

Bill

loomup comments, "...slips out of third gear...."

Slipping out of third is very common. Fortunately, this usually can be repaired without removing your trans. If lucky, you only need to adjust a shift lever on your trans. No so lucky, rebuild or replace a few parts mounted inside on your side shifter plate.

Here is a diagram. I have underlined in red suspect parts. Study this diagram so what I write will make sense to you. Best to open this graphic link in a new browser window so you can switch back and forth between my graphic and here.

3 Speed Trans

I will work at keeping this simple.

In my diagram, look at the two shift levers on the outside of a trans, underlined red "LEVER". Those are clamp on levers with serrated teeth. Those will slip around when loose.

Shift your truck into neutral, look under your truck to note the positions of those levers. Shift your truck into 3rd gear. Look under truck to note which lever moved and which way. This is third gear.

Get under your truck, remove the shift rod, usually a cotter pin and washers, remove this WITHOUT MOVING the trans shift lever. Once the rod is off, grasp the trans shift lever and discover if the lever will mover farther in the SAME direction when shifting into third. Move the lever as far into third position as possible. If your shift rod will not slip back into the hole WITHOUT MOVING the lever, you need to adjust this shift lever.

Release the clamping bolt, maybe spread the clamp a little with a screwdriver, pull the lever off the trans. Slip the lever back on just a little bit, just enough to make sure the trans is all the way into third gear. Gently remove the lever again. This time, slip the shift rod back in the lever hole, lift the shift lever and rod up, take out any slack in your shift mechanism by pushing or pulling, then carefully slip your shift lever back onto your trans WITHOUT MOVING the large shift rod protruding from your trans. Now clamp it back up. Install your washers and cotter pin on your shift rod.

All you really have done is to make sure your column shift lever is fully engaging third gear rather than partially.

Road test your truck.

If this problem is still present, you will need to rebuild or replace a few parts on the inside of your shift plate mounted on the side of your trans.

Look at my diagram, find SPRING and FORK, both underlined with red.

Those two springs and associated steel balls, red underlined "SPRING", are "detent" springs which hold a shift fork in position, keeps the fork locked in place. Those springs can be soft or broken. You can buy new springs on the web.

Look at the two forks, red underlined "FORK". Those forks do wear, do become too thin where sliding gears make contact. This is a very small area on "tab" like ends. Wear is easy to spot, looks like you used a grinding wheel on a small area; rough and a high ridge.

Two solutions for a worn shift fork. One is simply to buy a new or good used fork. The other is to take your fork to a machine shop to be specialty arc welded where worn, than machined and polished.

Shift your trans into neutral, set your parking brake or chock your tires. Take your side-plate off, springs and forks will come out with the side plate, and be ready for a lot of trans oil to come out, very messy. Note the relative positions of everything, you need to reassemble just like when this came out. Taking a photograph is a good idea.

Shine a flashlight into your trans, look around for worn gears, broken teeth, wear where the shift forks fit. Stick your fingers in there and test for excessive looseness but do NOT move those gears out of position; just gentle testing.

Now you can inspect the forks. Upon taking the plate mechanism apart, you can look at your detent springs mostly for curiosity. Replace those springs whether broken or not. You cannot easily test for spring load, simply replace those.

Worn fork or forks, you decide if to replace or to have a machine shop repair those.

Shop around, you might find a good deal on springs and forks, just buy all of those if a good price.

Reassemble your side plate then mount back on your trans with a new gasket. You will need to have your forks back in the same position so those will slip over and engage gears. Might have to wiggle your forks around to get the right alignment.

Top off your trans with gear oil. Road test. If still a problem, you need to completely rebuild your trans with giving attention to spacers, shims and wear on sliding gears; too loose inside. This is rarely a problem. Almost always either detent springs or worn shift forks.

Again, carefully adjust your shift levers before anything else, this is a common place for a problem. If not, then remove your side plate and go from there.

Billyray

I had an old 3 speed that i would describe as jumping out of gear. It would make quite a bang when it did it. Not sure about slipping out of gear. I drove that transmission till it grenaded itself, then replaced it with a t10 4 speed. If your truck has a torque tube, transmission choices are limited. If you ever put an opendrive axle, you will have many more choices for transmissions including, but not limited to the t5, t10, muncie m21 and m22, sm420, sm465...

Three speed transmissions from 1949 to 1954 have a rear mount casting that bolts to the back of the transmission. Whem the bushing in this part becomes excessively worn it will cause vibration of the front universal joint and it will jump out of gear at highway speeds. Fix by replacing the bushing. Worn synchros will also cause this condition, as well as worn shifting forks.

Billyray,

Thanks for the helpful and clear advice and instructions.

. . . Those two springs and associated steel balls, red underlined "SPRING", are "detent" springs which hold a shift fork in position, keeps the fork locked in place. Those springs can be soft or broken. You can buy new springs on the web. . . "
Suggestions on where to look for these parts on the web would be appreciated by many people.

. . . Shop around, you might find a good deal on springs and forks, just buy all of those if a good price. . . "
Again, suggestions on where to look for these parts on the web would be appreciated by many people.

Here is the 2nd & 3rd shift fork. A core is needed - they must have these rebuilt.

Is the reverse-first fork not usually a problem?

Thanks,

Another part that should be mentioned is the 2nd and 3rd gear clutch. I find most of them to be worn out most of the time. Somewhere in 53 or so they changed from a GM p/n 3705112 to a p/n 3713535. The difference is easily identified because the older style has two dogs and the later one has 4 dogs. The only source for this part that I have found is eBay. Used ones are usually not worth installing. The transmission has to be disassembled to install this part.

Thanks for the advice and the part numbers, Kenneth

By the way, I recently bought a couple of the forks NOS on eBay from a seller called dmedennis for $35 each. I have probably bought a couple of thousand dollars worth of transmission stuff from him, mostly for my BW overdrives, but he has an unbelievable amount of NOS stuff that is either OEM or old stock made in USA.

tclederman asks, "Suggestions on where to look for these parts...."

crenwelge up there has this right, Ebay. This is your best source for vintage parts. Frustration is working Ebay will sometimes take months, even years, to find parts you want. crenwelge also gives very good advice to look at specialty Ebay stores, those which exclusively sell vintage auto parts. Look for "NOS" parts, a safe bet because of being OEM parts.

Ebay can be frustrating, can be time consuming, there is no master parts catalog to use. However, you will eventually find what you need and usually at a decent price. You must be patient and must be willing to work at searching Ebay.

crenwelge and I probably have placed bids against each other.

On detent springs and other odd parts. Often you have to substitute in other brand parts. I am collecting parts to rebuild a 202V Clark trans build back in the Forties. This is in my big 1948 GMC. I want detent springs. I ended up buying Ford brand detent springs for a 205V Clark. I know the detent springs are the same because only differences in a "Ford" brand Clark transmission and a "GM" brand Clark transmission is the size and spline count of the input shaft, ignoring bellhousing bolt patterns.

tclederman, this is when direct experience over decades pays off.
This also pays to ask old farts around here for advice; you are drawing upon their decades of experience. Like others, my old fart experience goes back over three decades, all Chevy trucks with a few Chevy cars tossed in.

I will touch upon detent springs and other parts next post.

This is time consuming. To finds parts elsewhere than Ebay, use the Google search engine. You will NOT find parts by searching for 'transmission detent spring' but will find stores which might have those with 'classic truck parts' and similar terms.

Some Google search terms:

antique truck parts
vintage auto parts

Those two, leave out 'parts' and search again.

classic automotive
classic truck
old car parts
old truck parts
vintage cars

Those type of variations lead to hundreds of web pages.

truck parts vintage OR classic

This leads to lots. Note my "OR" in there. Google will find 'truck parts' then find 'vintage' OR 'classic' for the rest.

Google is your friend, Google will drive you nuts for hours.

Save your good finds in your browser bookmarks. I have a master category labeled 'NAPCO' for my four wheel drive truck. Under this category, 'trans' 'leaf springs' 'transfer case' 'rims' on and on. I subdivide into to specific part types. When I find a decent web page, either just info or a store, I will take a few minutes to add a page into my bookmarks under the right category.

In about a year, you will have hundreds of bookmarked sources. This is well worth the effort.

Much of this is planning ahead. I built myself an attractive but large storage room here on our land. Inside, looks like an auto parts store. I have sections, '48 GMC' - '52 Panel' - '56 NAPCO'- 'Generic' and in those sections I stash all my collected parts, accordingly. I am planning ahead for projects, such as rebuilding an old Clark trans. I collect all my needed parts, from gaskets to gears, before even dropping out the trans. Some parts I will need, some parts I might not need, but I have those.

In the case of an old 235 six cylinder, I actually bought one from a local boy. I collected my parts, rebuild this engine top to bottom, added an alternator and A/C compressor, dual carbs and all that, including those antique 'high lift' intake rocker arms. Took two years to collect parts. Now I have a rebuilt engine on a roll around stand ready to install. When down to a restored rolling frame, I only need to drop in the engine. Same is true for my trans and transfer case; all are ready to go.

This is time consuming, tclederman, but saves frustration. You can still drive your old rust bucket truck while you get together everything you need for restoration. Nothing more aggravating than having your truck sitting in your driveway for a year while you look for parts. Get your parts first, rebuild things first, then take your truck apart. This makes for a smooth and fun restoration project; all you need is ready and waiting.

I even collect doors, fenders and cab parts beforehand. Fix those up, do a custom paint job, wrap 'em with washed soft duck cloth painter's tarps from Home Depot, then continue on with finding parts. You will actually save money by finding bargains before you are ready to use those parts.

tclederman, follow this advice of crenwelge to search Ebay, follow my advice to spend a lot of time searching the web, both 'planning ahead' methods really pay off in the long run.

Billyray

tclederman, on detent springs and balls, don't sweat those balls nor your own. You will not need new detent balls. Only exception is when you are working with a totally rusted out transmission, but then you should not buy a rust bucket trans to begin with.

Those detent springs are common to many different transmissions. Those springs are not made by GM rather by a supplier. Same springs are used by GM, Ford, Dodge and many others. Find similar three speeds of the same vintage years, buy detent springs when you find those, if a cheap price. Upon arrival, toss your springs into small plastic bag, write up a label, "1956 Ford", shove this in your bag with springs, then store away. Next set, "1951 Jeep Saginaw", store away. Next, "1947 Fleetmaster", store away. Collect yourself several sets, dozens of sets if cheap. Amongst those you will have the right set of springs or close enough. You can later sell on Ebay what you do not need, or simply keep them for the future.

Detent springs only need to be 'about' the right length and 'about' the right diameter. A little too long, a little too stiff is better, never use too short of springs nor too soft. Those detent springs only control how 'firmly' a gear is held in place, not much else. Those springs only work right when your trans is in good repair. Those springs will not overcome major problems. Think of those springs as a "courtesy" for drivers, something to sorta keep your trans in gear. Purpose is solely to keep gears from gently "drifting" out of alignment, like when you are coasting along downhill, keeps gravity from moving your gears around.

Don't sweat the small details, find some springs very similar, stiffer the better, and go with those. You might be surprised to find some generic springs which will work at a cheesy Autozone store.

On your shift forks, you write:

"A core is needed - they must have these rebuilt."

Yes, rebuilt at a machine shop. Price is about $60 on your web page. This is a good price, probably less than what a machine shop would charge you to rebuild yours. When a 'core' is needed to exchange, your new part will always be rebuilt. This is OK.

You ask,

"Is the reverse-first fork not usually a problem?"

Correct. Key term is "usually". Those gears are used less than second and third. Reverse is used the least. Wear is spread out over four tabs, less wear per tab. Nonetheless, replace or rebuild the fork anyhow.

When you go through the trouble of dropping out a trans, or pulling an engine, go ahead with a full rebuild, do this right. If not, you will regret this later when something else fails.

Gears almost never need to be replaced. This only needed when a tooth is severely broken or other major damage. A little bit of rounding on teeth corners, no big deal; shifts smoother.

Sliding parts, like a sliding clutch gear or a sliding second gear, take a look at where the shift forks engage. Shined up from use, just fine. Should there be a 'ridge' then this is a problem.

Bearings and seals, those are to always be replaced no matter how good those look. You cannot precisely measure to determine if bearings are out of tolerance. Only a few thousandths out of tolerance causes a noisy transmission. Most often, you can pull a part number off the side of a bearing, like a Timken number. Same is true for seals. Easy enough to look up a catalog bearing or seal part number with disregard to what year and model of car. Bearing, seal and gasket kits are all over the web.

There is a boy on Ebay who sells complete gears sets, synchros, bearings, seals and gaskets, I mean the complete works, everything inside a transmission. A bit pricey, $200 to $400 but you will have virtually a brand new transmission good for fifty years or more.

Don't be afraid to rebuild a transmission. Those are so darn easy. Just get yourself a shop manual, or copy of instructions from a shop manual, a cakewalk. Old 'Motor Manual' books are available on Ebay, $10 to $30 on the average. Only need to be careful what years are covered. I have a collection covering about 1936 through about 1970, both car and truck versions. If you need a copy of instructions, just ask. Obviously I have a Motor Manual covering your transmission. You will be more pleased to have a manual of your own; loads of info about all aspects of your truck.

Don't be afraid, just use a bigger hammer.

Billyray