Need advice on feasibility of replacing 5th/reverse fork without removing tranny

[lindburly]

I have a 97 4.0, 4wd Ranger with manual trans.
The previous owner had put in a clutch meant for a 3.0 and I had to get both the clutch and the trans. replaced. Purchased a rebuilt trans. from Zumbrota Drivetrain and had it professionally installed. It lasted 4 months before 2nd gear went out. I got another one from Zumbrota and now, after 12 months (no longer under warrantee) it is popping our of 5th gear when under any amount of load. All the other gears are fine. I suspect a worn 5th/reverse fork and/or worn slider, both of which can be serviced by removing just the tail section of the trans.

It seems to me that it should be feasible to fix this myself by pulling the transfer case and removing the tail of the trans. housing without pulling off the whole trans. After studying all the material and videos I can find on rebuilding the M5R1 trans. I think it should be possible to do it that way and would save a whole lot of work and expense.

All of this assumes that I will be able to remove the top cover of the transmission through the access panel in floor of the cab. Can anybody confirm for me that access panel opening is large enough to do that? My understanding is that I will have to engage 2 gears through that panel in order to lock the trans. so I can loosen and then tighten the big nuts on the output and counter shafts. The other challenge will be removing the pressed-on bearing on the output shaft. I would lever it out by tapping the inside edge of it with a dull chisel as I rotate the shaft as shown in this video:

. (I would reinstall it by tapping on a piece of pipe held against the bearing. It looks like the removal and reinstallation of the rest of the parts should be fairly easy from under the truck.

Anybody have thoughts on whether I should try this? I know removing the transfer case is not going to be fun.

 

[SenorNoob]

Transfer case is definitely not fun, but; trying that repair in truck sounds worse to me.
If you take the whole plate out of the floor it might be do-able but you'll have to pull the carpet up.

 

[sgtsandman]

I would drop the transmission instead of doing the work in the truck. I also recommend dropping the transfer case before dropping the transmission. I learned that one from experience. Saving some steps before hand doesn't always save work in the long run.

 

[DRanger024]

I just did this exact thing after I rebuilt mine and installed the 5th/reverse slider backwards. I didn't take any pics of the process but it is doable. And it sucks. My only advice is to be prepared for everything to want to slide off the shafts when you start disassembly. You would be better off pulling the trans completely out.

 

[lindburly]

I pulled the carpet up and took off the inspection plate this afternoon. It appears that I should be able to get the trans. cover off with wobblies if I cut into the floor a little bit for better access to the bolt in the front right. I'm going to try to take the transfer case off tomorrow. I really don't want to take out the transmission cause I know gears 1-4 are good and the clutch is good. I'll report back and try to document it a little bit in case someone else is in a similar situation. Thanks for the help!

 

[DRanger024]

I pulled the carpet up and took off the inspection plate this afternoon. It appears that I should be able to get the trans. cover off with wobblies if I cut into the floor a little bit for better access to the bolt in the front right. I'm going to try to take the transfer case off tomorrow. I really don't want to take out the transmission cause I know gears 1-4 are good and the clutch is good. I'll report back and try to document it a little bit in case someone else is in a similar situation. Thanks for the help!

No need to trim anything at all. Take the transfer case out and remove the transmission crossmember and let everything hang from the motor mounts. You should be able to get at all of the top cover bolts and pull the top cover through the floor at that point. I would advise you get under there with an air gun and blow out any loose crap before you remove it or be prepared to flush the case out. I used a flex head ratchet and a 12mm deep well socket to remove all of the cover bolts. Put some rtv on the threads of the reverse idler gear bolt and the 5th/reverse shift fork shaft retainer bolt before you put it all back together.

 

[lindburly]

Thanks! After looking at pictures of the full top of the transmission, I realized that I couldn't see the whole thing through the access panel and that it would be impossible to remove it that way. After watching videos on rebuilding the trans. outside of the truck, I was hung up on the idea that you needed to open the top in order to put it into 2 gears in order to lock the shafts for removal of the 2 big nuts. I woke up this morning realizing that that's probably not necessary with the trans. still attached. Seems to me I should be able to lock the shafts by just putting it in gear and stuffing some 3/8" rope into one of the spark plug holes when the piston is down. The only parts I want to work on are in the tail. After removing those nuts, I should be able to put it back in neutral and remove 5th/reverse lever. Am I missing anything here?

 

[Eddo Rogue]

Dropping is not that bad. As mentioned the transfer case is a bit of a PITA, but no BFD. Besides it would allow other things like inspecting clutch, pilot bearing, u joints, splines etc....maybe a power wash and some fresh fluids in the trans and t case. I am biased against messing with bodywork like removing that interior plate, they never seem to go back on the same, making the cab lounder...

 

[DRanger024]

That should also work. You’ll still want to pull the crossmember to make it easier to get at the top extension housing bolts.

 

[DRanger024]

Dropping is not that bad. As mentioned the transfer case is a bit of a PITA, but no BFD. Besides it would allow other things like inspecting clutch, pilot bearing, u joints, splines etc....maybe a power wash and some fresh fluids in the trans and t case. I am biased against messing with bodywork like removing that interior plate, they never seem to go back on the same, making the cab lounder...

It’s only 4 bolts and there’s not really much of a seal on it. As long as you don’t bend the plate, it’ll be fine.

 

[lindburly]

Here's an update:
I managed to pull the transfer case, took off the trans. tail housing, and disassembled everything down to the 5th/reverse fork. Once there, I realized that I can't remove that without taking the top off the trans. because the fork is locked in by the lever that that is locked in to the 5th/reverse shift rail, which is locked in by the cover. It all seems to have been pointless anyway because I can't see any wear on the fork, the slider, or the rounded end of lever that engages the fork. (I stuck a little mirror up in there for a really close look and there are virtually no gaps.) I'm not sure if it's worth the effort to remove the top when I don't see any wear. The only thing I saw that seemed a little odd is the reverse idler and countershaft gears protruded about 3/16" more than the output shaft gears.

I read that worn shifter bushings can be another possible reason for popping out of 5th gear, but that was the first thing I checked and they were in good shape. I don't feel much confidence that I'm going to be able to solve the popping out of 5th problem. I'm at a loss.

 

[lindburly]

So I found this article which does a better job of explaining the pop-out problem than anything I've see so far: http://www.wcengineering.com/articles/popout.html
They say that pop-out is most likely caused by shaft movement from the force of the helical gears pushing against each other. If there is any bearing wear that allows slight additional movement of one of the shafts, the little springs in the slider assemblies are easily overpowered by the force of the helical gears, which causes the pop-out. My pop-out started 12 months after my remanufactured transmission from Zumbrota Drive Train (which is now owned by Midwest Transmissions) was installed. It's hard to see how I would get that much bearing wear in just 12 months of very limited driving (during covid shutdowns). I wonder if the 3/16" misalignment that I found between the outer faces of the gears could have contributed to the problem?