F150 truck transmission weirdness

Factual Questions
1

I have an old beater 1990 F150 truck. It started out its life as an automatic and someone switched it over to a manual at some point. It’s a king cab with a full bed, so it’s a bit long. As such, I usually back it into my driveway so that I can pull straight out, since if I have to back it out of the driveway the back end starts going out onto the road before I can see around the trees to see what’s coming down the road. When I come home, if someone is behind me, i pull over and let them pass. This stops idiots from trying to zoom around me while I stop to back in.

A few months ago, I did exactly that. Only when I went to pull forward (in 1st gear) I heard a loud pop, and then the transmission felt like it was in neutral. Ooh, that’s bad, I thought. I put it into second, and that worked, but when I got to the driveway and put it in reverse, it again felt like it was in neutral. I went through the parking lot at the day care across the street (since I couldn’t back up) and this time went straight into the driveway and parked it.

Anyway, I was working on paying off my house and I loaned my son some money to buy a car, and this is far from my only vehicle, so the truck sat for a few months. Now that I’m financially in a better position to get it fixed (even if it needs an entire new transmission) I decided to take it to ye ol local transmission shop. I figured it still had 2nd gear and maybe some others, so even without 1st and reverse I could probably limp it across town, no biggie. Since it sat for so long, I put the battery charger on it last night, then this morning I fired it up.

And now here’s the weird thing. Everything works fine. All of the gears work. It’s like nothing ever happened to it.

I didn’t do anything to it for the last few months. It just sat. My sons pushed it around in the driveway a bit to make more room so #1 son could get his motorcycle past it more easily, and at first they tried to push it while it was still in gear (which didn’t work very well). Other than that, no one has touched it.

Now I’m just an idiot back yard mechanic (or front driveway mechanic), and while I think I have a fair understanding of how a manual transmission works, I’ve never had to fix one. But everything I can think of that could have been wrong with it involved something mechanical and fairly drastic that couldn’t possibly fix itself. I know that first and reverse on some transmissions end up using the same shafts and gears with an extra gear used to spin the main shaft backwards for reverse, so I was thinking that something mechanical related to those shared components went ka-blooie (how’s that for a technical term). I was thinking something along the lines of a broken gear or a broken shaft or the shaft somehow popped out of place. None of those would fix themselves, though.

So, does anyone know what could have happened to this thing and why it works now?

I drove it around the neighborhood a few times and then drove it into work today. It works perfectly. Well, as perfectly as you’d expect a 25 year old beater truck to work, anyway.

2

when the thing first went “bang” and felt like it lost first gear, did the shift lever move back into the neutral position?

3

Yes, it did. My first thought was that it just somehow popped out of gear.

4

check your shift linkages (if it’s not a top-loader) for slop and worn bushings, and pull the shifter boot and inspect any pivots, mounts, and/or bushings on the shift lever. internal transmission problems (especially on a manual) typically don’t “un-bad” themselves.

5

There is some slop in the linkages. How would that cause it to fail to engage 1st and reverse though?

6

they’re deflecting enough where they can’t physically move the dog clutch(es) into mesh? I’m doing little more than guessing here since I can’t see your transmission. usually problems with manual txs holding gear have to do with the shift mechanism or some other thing that lets things get out of alignment (e.g. worn motor/trans mounts.)

7

The gear lever is held in (to the linkage arms) with springs. Without the spring you can lose the ability to grab some gears while it still works for others…

Its possible that the spring wobbled and caught something (perhaps it re-hooked the proper attachment place ? ) so that the lever is now held “in” enough to get force and distance on the linkages.

8

With a DIY manual conversion, I would give a lot of credence to the “transmission wiggling around in the mounts” theory. You might try (carefully!) crawling under the truck and looking at the transmission while someone (with the parking brake on and their foot HARD on the brake pedal!) puts the truck in gear and slowly lets the clutch in. If they do it in first and then reverse, it should be somewhat obvious if the transmission is moving.

9

I was looking at some videos on youtube today about how to change the bushings, etc. on the shift lever. It looks like I can’t get to much without disassembling the transmission. I’d like to get some of the play out of the shift lever though, which looks do-able. Maybe that will prevent anything along these lines from happening.

I’ll try that this weekend. Thanks for the suggestion.

This thing sits pretty high off of the ground, so as long as I make sure no parts of me are in the paths of the tires it’s a pretty safe thing to do.