4 speed top loader jambing. Linkage or gearbox issue

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Stanglover

Stanglover

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Location
SW Ontario
My Car
1971 Mustang Mach 1, M code, 4 speed.
Looking for a heads up before I start pulling stuff apart and getting dirty.

First, the car is a 71 Mach 1, 4 speed manual. The top loader was totally rebuilt professionally back in 2012 and the Hurst shifter was sent back to Hurst last winter. I have never had a problem in the 11 years I've owned the car, but the other night, I was about to leave a local cruise-in when I could not get it out of reverse. (these lock in reverse and no, it was not the key stuck). I usually pull it to neutral before I start the motor. When I did start it in reverse, I was able to get it in neutral and then drive normally, no more issues. When it was stuck, there was a solid clunk noise from the area of the lock-out rod as I tried to get it freed up.

I have driven the car a few time since without issue, but this morning I backed out of the garage onto the street and for a time, could not get out of reverse. Once it did release, no more problems going to and back from a car show.

I've heard that the original shift rods can get jambed up, but I have never had that happen. So, has any one had this or a similar issue and can offer a heads up?

I'm pretty sure I'll be under the car in the next day or so, so it would be helpful if I knew what I was looking for. Lock-out rod, shift linkages, shifter or gearbox itself (Hope not the latter!!)

Geoff.

 
Last edited by a moderator:
Looking for a heads up before I start pulling stuff apart and getting dirty.

First, the car is a 71 Mach 1, 4 speed manual. The top loader was totally rebuilt professionally back in 2012 and the Hurst shifter was sent back to Hurst last winter. I have never had a problem in the 11 years I've owned the car, but the other night, I was about to leave a local cruise-in when I could not get it out of reverse. (these lock in reverse and no, it was not the key stuck). I usually pull it to neutral before I start the motor. When I did start it in reverse, I was able to get it in neutral and then drive normally, no more issues. When it was stuck, there was a solid clunk noise from the area of the lock-out rod as I tried to get it freed up.

I have driven the car a few time since without issue, but this morning I backed out of the garage onto the street and for a time, could not get out of reverse. Once it did release, no more problems going to and back from a car show.

I've heard that the original shift rods can get jambed up, but I have never had that happen. So, has any one had this or a similar issue and can offer a heads up?

I'm pretty sure I'll be under the car in the next day or so, so it would be helpful if I knew what I was looking for. Lock-out rod, shift linkages, shifter or gearbox itself (Hope not the latter!!)

Geoff.
Click to expand...
If you have ALL D1 shift rods, you will experience that OR WORSE the Locked in reverse and first at the same time.  Ford did a campaign in late 71 where they replaced the 1/2 rod with a D2 numbered rod that had more clearance in it ELIMINATING the binding issue.  

Mark

 
Looking for a heads up before I start pulling stuff apart and getting dirty.

First, the car is a 71 Mach 1, 4 speed manual. The top loader was totally rebuilt professionally back in 2012 and the Hurst shifter was sent back to Hurst last winter. I have never had a problem in the 11 years I've owned the car, but the other night, I was about to leave a local cruise-in when I could not get it out of reverse. (these lock in reverse and no, it was not the key stuck). I usually pull it to neutral before I start the motor. When I did start it in reverse, I was able to get it in neutral and then drive normally, no more issues. When it was stuck, there was a solid clunk noise from the area of the lock-out rod as I tried to get it freed up.

I have driven the car a few time since without issue, but this morning I backed out of the garage onto the street and for a time, could not get out of reverse. Once it did release, no more problems going to and back from a car show.

I've heard that the original shift rods can get jambed up, but I have never had that happen. So, has any one had this or a similar issue and can offer a heads up?

I'm pretty sure I'll be under the car in the next day or so, so it would be helpful if I knew what I was looking for. Lock-out rod, shift linkages, shifter or gearbox itself (Hope not the latter!!)

Geoff.
Click to expand...
If you have ALL D1 shift rods, you will experience that OR WORSE the Locked in reverse and first at the same time.  Ford did a campaign in late 71 where they replaced the 1/2 rod with a D2 numbered rod that had more clearance in it ELIMINATING the binding issue.  

Mark
Click to expand...
 Hi Mark, Thanks. That comes back to me now. I remember something along those lines, but weird that I have NEVER had an issue before. 

So, I guess I'm on the hunt for a D2 1/2 shift rod. In the mean time, I'm going to put the car up on a friends hoist and take a look and see IF I can fix it. Just strange that it should happen now.

Thanks for your reply,

Geoff.

 
First thing I would do is loosen the nuts on the slotted ends of the rods and put the 3/16" allen wrench through the sifter to get it all aligned and tighten all the lock nuts on the slotted ends of the rods. 

Not much else it can be I am not up on the rod jam thing for D1 D2?

I have always found it easier to go from reverse to 2nd. then to first to get going. Easier to align all the synchronize hubs it seems.

 
First thing I would do is loosen the nuts on the slotted ends of the rods and put the 3/16" allen wrench through the sifter to get it all aligned and tighten all the lock nuts on the slotted ends of the rods. 

Not much else it can be I am not up on the rod jam thing for D1 D2?

I have always found it easier to go from reverse to 2nd. then to first to get going. Easier to align all the synchronize hubs it seems.
Click to expand...
 Thanks David. I might need to readjust the rods again, been a while. I'm taking the car to my friends place tomorrow and put it up on his brand spanking new 4 post hoist. Heck, I help him install it, so why not! 

It's a strange thing, I did nothing different than I've done over the last 11 years and 16000 miles, never a problem other than it was always a bit 'sticky' going into 2nd., 1st to 2nd or 3rd to 2nd. until I had the shifter rebuilt. That made it much better, but still not great. I know when the box was rebuilt by a local guy who is reckoned to be about the best around here on top loaders, he replaced everything that was even slightly worn, so I do not think there is an internal issue, hope not at least.

I'm going to take a good look and get back on what I find or don't find.

Geoff.

 
I took the car and put it up on the hoist. All I found that was anything like suspicious was the reverse lock-out rod bushing, which I replaced. I did find the rod adjustment on 1/2 and 3/4 were off slightly, i.e. the 1/4" pin used to align the shifter levers, would not easily pass through. Readjusted the rods and a big improvement on the 1st and 2nd gear shift. Also easier to get reverse as well. The only other 'thing' I found was the fuel vapor return line had mysteriously got bent and was contacting the top of the rearward selector arm (that's what I'm calling it, not sure if it's 1/2 or 3/4!) Anyway got that fixed too. So I guess time will tell if it jambs up again.

Thanks to all for your comments,

Geoff.

 
I had a similar problem, but in my transmission's case there was wear in the case itself where the shift rod sits and it had to be machined out and a bushing installed. (Yes I am aware of the bad pub, but it was just there and I couldn't resist)

 
I had a similar problem, but in my transmission's case there was wear in the case itself where the shift rod sits and it had to be machined out and a bushing installed. (Yes I am aware of the bad pub, but it was just there and I couldn't resist)
Click to expand...
Jeff, not quite following you...…. or am I just missing something. Wouldn't be the first time for a brain fart!!

Geoff.

 
internally there is a shift rail for reverse. Where that fits into the case of the transmission, the case was worn oversized so the rail moved/deflected rather than just turning. Caused the same type problem you described. Case was drilled oversized and a bushing installed to repair it. See part Number 23

http://www.davidkeetoploaders.com/explodedview.htm

 
internally there is a shift rail for reverse.  Where that fits into the case of the transmission, the case was worn oversized so the rail moved/deflected rather than just turning.  Caused the same type problem you described.  Case was drilled oversized and a bushing installed to repair it.  See part Number 23

http://www.davidkeetoploaders.com/explodedview.htm
Click to expand...
 Ah, I see! No, I don't think that IS the problem, but a very useful heads up. If I get that happen again, I'll talk to the transmission guy who rebuilt the box. I'm pretty sure he installed new bushings and seals on everything that might be worn.

After I readjusted all the linkages and changed the reverse rubber bushing, It did seem much better. We'll see I guess.

Thanks for the clarification Jeff.

Geoff.

 
internally there is a shift rail for reverse.  Where that fits into the case of the transmission, the case was worn oversized so the rail moved/deflected rather than just turning.  Caused the same type problem you described.  Case was drilled oversized and a bushing installed to repair it.  See part Number 23

http://www.davidkeetoploaders.com/explodedview.htm
Click to expand...
 Ah, I see! No, I don't think that IS the problem, but a very useful heads up. If I get that happen again, I'll talk to the transmission guy who rebuilt the box. I'm pretty sure he installed new bushings and seals on everything that might be worn.

After I readjusted all the linkages and changed the reverse rubber bushing, It did seem much better. We'll see I guess.

Thanks for the clarification Jeff.

Geoff.
Click to expand...
 Hi, I have  a 71 Mach 1 with  Toploaders RUG-AJ gearbox ( originally 1968/69 Fairlane ?).

I had an issue once that the gears ( some of them) got jammed and it was impossible to  change gears with the shifter....I had to free them going under the car which was awkward to do on the street - exhaust pipe is hot:)

Long story short... finally the reason was  that the  linkage spring clips that hold the rods in place had become out of tension and  were touching the linkage. I changed  new spring clips and the problem was gone !

Sometimes the cure  is  simple  and inexpensive...

 
internally there is a shift rail for reverse.  Where that fits into the case of the transmission, the case was worn oversized so the rail moved/deflected rather than just turning.  Caused the same type problem you described.  Case was drilled oversized and a bushing installed to repair it.  See part Number 23

http://www.davidkeetoploaders.com/explodedview.htm
Click to expand...
 Ah, I see! No, I don't think that IS the problem, but a very useful heads up. If I get that happen again, I'll talk to the transmission guy who rebuilt the box. I'm pretty sure he installed new bushings and seals on everything that might be worn.

After I readjusted all the linkages and changed the reverse rubber bushing, It did seem much better. We'll see I guess.

Thanks for the clarification Jeff.

Geoff.
Click to expand...
 Hi, I have  a 71 Mach 1 with  Toploaders RUG-AJ gearbox ( originally 1968/69 Fairlane ?).

I had an issue once that the gears ( some of them) got jammed and it was impossible to  change gears with the shifter....I had to free them going under the car which was awkward to do on the street - exhaust pipe is hot:)

Long story short... finally the reason was  that the  linkage spring clips that hold the rods in place had become out of tension and  were touching the linkage. I changed  new spring clips and the problem was gone !

Sometimes the cure  is  simple  and inexpensive...
Click to expand...
 Interesting. I am not sure at all, but on the 71 Mustang box, there are no spring clips. The rods just press fit into rubber like bushings. The shifter end of the rods has the adjustment slots where the bolt like inserts also just press fit into bushings. Perhaps that was a change for the earlier box you have.

I talked to my gearbox guru today and he told me that it was more than likely the rod bushing need to be changed, A small amount of free-play can cause the rods to jamb up. I have new bushing and will change all tomorrow. I also have a bronze bushing to install on the reverse lock-out rod where it fit to the steering column plate.

I don't anticipate any more problems after that. 

Thanks to one and all for your help, suggestions and input.

Geoff.

 
Update: pretty sure I have that issue solved, loose rubber bushings and need for slight adjustment on the linkage. The rods were able to move enough to perhaps cause them to jamb. There's not much room for error under there!

Geoff.

 

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