Noise in FM146

[4x4junkie]

Yeah, yeah, (POS) I know lol

I'll start with that it does not seem to be the normal failure of the input shaft bearing...
It does sound like some other bearing starting to go out though (not a gear whine).

It sounds speed-related to the trans OUTPUT shaft, but only in 5th gear (no noise in any other gear) and is more audible when under load.
I drained the fluid, couldn't see any distinct metal flakes, but it was a bit grayer than the normal honey color of clean gear oil, and had a slight pearl-like appearance (oil was changed maybe 3000miles ago, trans has around 155k miles on it, a lot of it hwy).

I guess in any case it's lookin like it's time for an M5OD, but it's kind of got my curiosity since it doesn't seem to be the typical failing on these things

Any thoughts before I pull it out and tear into it (not to rebuild it, but just to see what it is)?


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[2manyfords]

My FM146 makes a similar noise.
I think it is something to do with the OD gear bearing and are also known to fail but not as often as the input shaft bearing.

FWIW... mine has been whining in OD for a couple of years now. I stopped using OD and it's still hanging on.

 

[Totalled]

You're geared deep, so you're using 5th allot. 5th gear has an inadequate lubeing problem in the mitsu. So it's burning up.

Find an M5OD.

 

[4x4junkie]

Interesting.
My BII used to be geared 3.73 with the dinky P205 tires (it's not much deeper than it was before), so I'm sure it's seen plenty of 5th gear time.
I guess screw it, drive it till it blows lol. Not like a Mitsu is worth much even if it were still good (at least I wouldn't think...)

Find an M5OD.

Yeah, that's definitely the plan.

 

[Totalled]

Right. But it's not new, and it's "seeing" more load now. Lifted (wind resistance) and larger tires ( weight and rolling resistance)

 

[rickcdewitt]

mine started with those symptoms,progessed to a noisy third and large grits and was so trashed apon removal that it was cheaper to replace than rebuild.of course i replaced it before i knew the large flywheel and m5od would bolt right in

 

[MAKG]

My FM145 did something quite similar.

As has been mentioned, the 5/R chamber is not very well lubricated in FM14x transmissions. You never use reverse very much, so this shows up in 5th. It comes from overusing 5th. Even with deep gears, under heavy sustained loads, you really want to be in 4th.

to confirm, you have to remove the extension housing; you'll see pitting on 5th and counter-5th.

It's a relatively easy repair; you replace the 5th and counter-5th gears. These are not hard to find used (it's not the usual failure), but you do want a matched pair if at all possible. The shafts do not have to come out, but both the locknuts must be removed.

Or you can just put an M5OD in.

 

[4x4junkie]

That does make sense, I just drove up north and it was after going through the mountains of No. Calif. I noticed a slight chatter starting to become audible in 5th gear.

I knew it was a POS, but damn! I even made a point not to hold it floored in any gear outside of 4th too. :banghead:

M5OD is going in for sure, I'm not gonna bother trying to repair it.

Thanks for the info on that though.

 

[rickcdewitt]

MAKG is there anything you can do to help these trannies with lubrication?enlarging ports or something?i have a spare tranny pan that i want to make into a deep sump with cooling fins or air tubes going through to help.probably polishing a turd but the last fm-146 lasted 130,000 miles and if i can help the new one to reach the same mileage with the extra abuse of all the trucks mods(and my right foot) i'll be happy.i paid 1000$ for a reman. tranny and want all the bang for the buck i can get. the tranny shop said that the gears are a close tolerance in these trannies and when the bearings go out it takes the gears with them.is that probably also the case in junkies rice box?

 

[MAKG]

You can try to widen the passage between the two chambers, but honestly the RIGHT solution is to take it out of 5th whenever it is under heavy load. The truck will drive better that way anyway, as will all vehicles. You'll need a milling machine to widen the passage; there isn't any room to do it with a drill (you can't take anything out of the bottom).

 

[rickcdewitt]

thanks MAKG,you called it,5th is pretty worthless on anything but flat ground(33's and 4.10's don't help).can you think of any drawbacks to the deeper sump,other than getting in the way when pulling the tranny?would baffles be a good idea?that and a big magnet on the pan(and my fingers crossed)might help eh?

 

[4x4junkie]

IMO, the RIGHT solution is actually swapping in a trans that's worth a shit.

I don't think a deeper sump would help, if the fluid isn't getting back there in the 1st place, then more fluid below I don't see doing much, you'd need to widen the oil passages up more (maybe overfilling it could help though? I couldn't say for sure though).
The cooling fins (and magnet) couldn't hurt though.

anyway, I got me a M5OD (the semi-elusive 2.9L 4x4 version, too ). Now I just have to install the thing ugh.

 

[rickcdewitt]

IMO, the RIGHT solution is actually swapping in a trans that's worth a shit

anyway, I got me a M5OD Now I just have to install the thing ugh.

yeah i think i'll be swappin' in a trans and MOTOR(91 exploder) thats worth a shit!