M5R1 notchy 1-2 shifting

[masospaghetti]

I recently rebuilt my M5R1 transmission and the shift action from 1-2 is inconsistent, sometimes smooth, sometimes really notchy. 2-3 can be a bit inconsistent as well but not as bad as 1-2.

The hub/slider engages easily for the first half of the throw, but the trouble seems to happen on the 2nd half. I've tried different different fluids, the best seems to be plain Mercon ATF.

I installed all new synchro rings and the hub/slider assemblies are new. The 1-2 hub/slider was a new old stock OE part. 3-4 was a new aftermarket hub/slider. It's been about 1000 miles since the rebuild. I did not replace the gears on the main shaft.

If it matters I have the 2.9 gearset (steeper 1-2-3 gears).

Any suggestions or comments?

Edit: Added some pictures from my endoscope thru the fill plug of the 2nd gear assembly.

 

[MrQ]

I had the same issue. Not a rebuilt, but it turned out to be a bad slave and/or air bubbles in the line. 1-2 shift I had the clutch to the floor, sometimes it would go sometimes it would grind. Didn't matter what I did or how careful I was it just randomly occurred. Same thing with the 2-3 shift. Sometimes I could get it smoothly into 3rd without fully depressing the clutch and sometimes I had to slam the pedal to the floor to slot it in.

Put in a new slave and clutch set and bled the system. Problem gone.

 

[masospaghetti]

Thanks for the tip. There's almost no slop in the clutch pedal (visually can see the slave moving), but I will try bleeding the line again.

 

[masospaghetti]

I bled the clutch system again. Unfortunately the problem remains.

The possible causes that I can think of:

1 - New slider hasn't broken into the old gear (will it ever?)
2 - Worn main shaft/bearings (wouldn't I be getting noise?)
3 - Old gear is worn out

Any other "hard parts" that could cause shift problems?

I'm contemplating either tearing it down again or just getting a remanufactured box from Zumbrota to be done with it.

 

[410Fortune]

I know it sounds petty but did you replace the shifter arm bushings? (the nylon rings at the shifter ball base)

 

[masospaghetti]

I know it sounds petty but did you replace the shifter arm bushings? (the nylon rings at the shifter ball base)

Yeah I did. The bushings came in the rebuild kit. Thanks for the tip.

 

[Rick]

FWIW mine has always shifted the best when I use Mobil 1 automatic transmission fluid. After a suggestions I swapped to Redline once. I filled it with Redline and went for a test drive. I drove the Explorer from my house straight to the auto parts store for some Mobil 1 because the shifting was so difficult. It's pretty crazy how sensitive the M5R1 is to tranny fluid types.

 

[410Fortune]

I concur with the red line, I built a 4.0 V6 5 speed 96 ranger for a friend, he removed the mercon III I had in there and went to redline in the trans and t case. Few months later we replaced the trans. A year later we replaced the t case. I warned him, I don't like Redline fluids....

 

[MrQ]

I concur with the red line, I built a 4.0 V6 5 speed 96 ranger for a friend, he removed the mercon III I had in there and went to redline in the trans and t case. Few months later we replaced the trans. A year later we replaced the t case. I warned him, I don't like Redline fluids....

Funny how the oil snobs swear by these "premium" oils, basically saying that paying a lot of money is tantamount to higher quality. Not going to get into an oil debate, but the Valvoline ATF I use in my M5OD is a lot better than what was in there before and it cost a whole lot less.

My mom had a story about a high end grocery store that put out fresh strawberries for $0.99. But sales were sluggish. Thinking that the price was causing an image issue the store jacked up the price to $2.99. Surprisingly, the strawberries flew off the shelf. Exact same strawberries, but people's perception of cost vs quality made them look more appealing with a higher price...

which is also the reason people still buy BMW's.

 

[410Fortune]

Mobile one or Valvoline that is all I run unless I am forced to do otherwise...........

 

[masospaghetti]

I've been driving hoping the shifting would get better as things wore in, but they have not. So the transmission is out again.

The only other thing I can think of is worn dog teeth on the gears themselves. You can see in the second picture 4th gear is new and has nice sharp dog teeth, the other gears do not. But I am far from certain that is the only cause.

Here is 1st-2nd gear:

And here is 3rd-4th, bottom is 4th gear - see the nice pointy teeth:

So, I'm biting the bullet and buying a reman box from Zumbrota Drivetrain via RockAuto. Will arrive in 2-3 weeks, stay tuned!

 

[Rick]

Thanks for the update. Man that's frustrating when you put so much work into something and it doesn't work out right. Been there...

 

[RangerX]

Have you considered the possibility that the clutch is not perfectly bled?

 

[masospaghetti]

Have you considered the possibility that the clutch is not perfectly bled?

Thanks for the comment. I have, I tried bleeding the system twice on the latest round (once with a plastic syringe to force fluid down the hose).

4th gear shifted smoothly, consistently. I figured if the clutch was the problem it would happen in all gears equally. I did also check visually that the slave cylinder started to throw as soon as the pedal was pushed and there was almost no play in it.

 

[masospaghetti]

So after a few months with the Zumbrota-remanufactured transmission, I can say that the problem has been resolved.

A bit unsatisfying. I wanted to know what caused the problem in the old transmission, but more than that I wanted the shifting fixed.