The Stovebolt Site Forums The Shop Area Driveline 54 3100 still slides out of high gear

Got the truck driveable, made a few local 15-25 mile trips and she still slides out of high gear. Torque tube 3sp column shift. New pilot is snug. New needles and bearings. Good looking gears. New rear bushing. Bell tight to engine and trans. Some wear on the synchronizers as they need a smooth/easy shift to 3rd or down to 2nd. 2-1/2 pt period Amoco 90wt. Feel full shift to 3rd but also feel it easing out as I drive. Thoughts?
Jethro.

Something to read that may help: https://chev235guy.blogspot.com/search/label/Jumping%20out%20of%203rd%20gear

Is the oil you used 90wt mineral oil? If your using a modern oil, it may be too slippery for the synchro’s to work properly.

Here is a thread explaIning the importance of using the correct oil. https://www.stovebolt.com/ubbthread...752/re-transmission-oil.html#Post1452752

I'll get some from tractor supply or napa. Probably jack the rear up and run some diesel in it for a few minutes to clean it out if that sounds reasonable. Thanks. Jethro.

I don't think you have to wash it out with diesel. Just drain it well and fill it up with the right stuff.

Once the synchronizer matches the gear speeds and the shift collar engages, the lube won't make a difference. Slipping out of gear is a result of wear on the small male teeth on the input shaft that the synchronizer sleeve engages, and the corresponding female splines on the synchronizer drum. If there's any taper wear at all on those mating pieces, the sleeve won't stay engaged on the back end of the input shaft for direct drive. Both pieces will need to be replaced.
Jerry

Well, I drained the trans and the nice-looking Amoco 90wt had a caramel foam on top. Filled it with NAPA 90wt mineral and after slipping out once a mile down the road it didn't slip out again on a 12 mile ride. Drove it again later and it stayed in 3rd the whole way. Hopefully the change did the trick. Think I'll dump the rest of that Amoco down a groundhog hole.

Good to hear that the issue seems to be solved. Additionally, any place that changes oil will accept oil used for maintaining vehicles or at least tell you where you can dispose of it. No need to dump it into the ground.

I think he was joking about the groundhog hole.

Jetro in VA Don't do the groundhog hole,it'll contaminate the ground water

Fire ant nests are a lot more suitable places to dispose of used oil- - - - -those nasty little critters deserve all the lubrication they can get. I've been known to park an idling Diesel tractor over a big fire ant mound and create a little bit of a fuel leak by loosening a return line on an injector.
Jerry

I'm pretty sure he was joking about that. Everybody knows that pouring it down a storm drain is the best way to get rid of used oil.

OH! Your funny!