Run Away

So I bought an M2B4 for cheap in unknown condition.
Ended up being stuck in 5th, so I opened it up and took a look. I've never rebuilt a trans before so bear with me.
I'm not sure exactly what happened but it seems to me 5th gear on the mainshaft moved up and sandwiched/welded itself to the 5th gear syncho hub. Caused by 5th gear bearing failure????
It looks like I'll have to replace 5th gears on the main and countershaft, the spacer collar 4th and 5th ride on on the main shaft and then everything else above 5th gear on the mainshaft.



5th gear on the mainshaft did a little self-clearancing on the casing.

See how there's lots of space between 4th and 5th gear here on the mainshaft?

Sandwiched

You can see the toasted bearing here

Pressed 5th gear off the mainshaft

5th gear, the synchro and the synchro hub all stuck together

Used a hammer+drift to get the synchro hub off, this is the backside

Spacer collar, end of mainshaft


Boy, the flash really makes things look bad



Now I'm looking for the cheapest way to fix this - I'm thinking buying another junked or good trans and making one good one out of the two. Locally there is a 5 speed from from a '93 accord being offered for sale for $60 in "good condition". Would I be able to press the 5th gear assemblies from this trans onto my M2B4 main and countershafts? Would I be better off putting the LSD diff from the M2B4 into a good trans? I don't particularity care about the ratio, 5th gear is just for cruising

94EG8

Tranny looks like it was run with no fluid, fifth welded itself to the mainshaft. Most or all of the rest of the gears probably got hot and are now soft as butter. If you can take a file to the gears they're junk. My advice, buy another tranny.

ion_four

The problem you have is that the M2B4 transmission won't be in the USDM Electronic Parts Catalog, so you can't just compare part numbers/dimensions on paper.

One thing I know through reading is that the M2B4 LSD is different than other M-series diffs and won't swap. However, that doesn't necessarily mean the gears/shafts won't swap.

Conveniently, I have an M2Y4 (USDM 97-01 Prelude Base) transmission apart, right now. SO, if you want some 5th gear shaft/bearing measurements, I can do that, as long as it's quick (I'm heading out of town for the holidays, tomorrow night!)

Did you figure out the trans was stuck in 5th without running it? Even though you have it apart, I'd get on whomever you bought it from, because I think it's pretty likely that "unknown" condition meant, "totally screwed up" condition

Honestly, that's a tough call as to whether or not you can salvage it. Maybe spend some time cleaning it up and see what a more knowledgeable person says? Alternatively, maybe you can find someone with an M2B4 with a blown diff, or cracked case and you can swap-a-roo the good parts between the two?

ion_four

Sorry to double up, but what does the diff look like?

If it's good, maybe you can swap in all the other Accord guts and cross your fingers!

Run Away

94EG8: Bah, not what I was hoping to hear. You're suggesting actually taking a file to some of the gears? Like to the face of the teeth and see if I get shavings or if it scratches or ???

ion four: Yes I realize that. If you're willing to get some measurements I'd really appreciate it. I guess the O.D. of the spacer collar 5th rides on, maybe the O.D. or spline count of the mainshaft where the 5th gear syncho hub goes?
Looking through hondapartsunlimited.com the 5th gear bearing is the same part number for a '93 accord LX and a '01 Prelude base, so that's promising.

I figured it was stuck in 5th before disassembly because it would shift into all gears except 5th. When in neutral and I spun the input shaft by hand the diff would turn as well at about the same ratio. When I tried to spin the input shaft when in gear, nothing would turn.

I bought it on ebay - seller advertised it as unknown condition, so assuming it's a core. Said it shifted into all gears and spun in neutral by hand but couldn't spin in by hand when in gear. Says he got it from a shop, didn't even know what it was. Thought it was an Integra LSD cable trans because it's cable shifted.

Haven't paid attention to the diff at all. Just snapped a few pics when I pulled it out, that's it.



Oh! Forgot to thank you both for the replies.

94EG8

Yes

Yes again, normally the gears are pretty hard and a file wont do anything to them, but if you can easily file a groove in them they're toast.

ion_four

Here we go...I get 37mm OD for the 5th spacer collar, and 31mm OD on the mainshaft 5th gear synchro hub splines, with 30 teeth. Here are pics to make sure we're talking about the same pieces!


Sorry, crappy caliper...I really need to get something "for real."



(I did measure on the OD of the splines, not the shaft...it's hard to tell in the pics.)

jlude90

only H22 or H23 gears will work. F gears have the 5th gear machined differently, but why not just the F trans on there?

ion_four

Do you mean the P series transmissions? I have an M2L5 from a Prelude S (F22 engine) and assume the 5th gear from that would at least work, since it's an M series...

Run Away

94EG8: Interesting, I'll give it a try and report back.


ion four: THANK YOU!! People like you make car forums awesome. I don't have the trans at home for me to compare but I will definitely measure and post pics.


jlude90: This is news to me, do you have specifics? I just did a quick google and some are saying there are clearance issues with the case and others are saying it just needs some spacers or something....can't really find any clear definitive answers.
I'd be swapping the the two matching 5th gears obviously so all they have to do is fit on the shafts, and I've already confirmed the bearing part numbers for an H22 and F22 5th gear is the same. Do you know if the M2B4 LSD fits into the F22 trans? As long as the bearing diameters and ring gear patterns are the same it should work I think?

Guy on the local classifieds just lowered the price of the '93 accord trans down to $40 so I sent him an email and I guess I'll find out myself. I'll be sure to report back with pics and measurements.
I don't actually have an H/F-series powered car to put this in, I just bought it because it was cheap. Once I finish a few other projects maybe I'll F23 swap my dd civic with this trans.

ion_four

NP man. Sometimes I seem to ask questions that go totally unanswered...so, I can't bitch too much if I don't help out other random people

Run Away

Okay so I got the chance tonight to play with the trans again...been busy with work and the holidays.

Pressed off 3rd/4th



28mm OD end of Prelude mainshaft

31mm OD middle of Prelude mainshaft


Accord trans I bought

I'm new to this but from what I can tell the insides of this trans were quite minty.
Accord vs Prelude mainshafts

I use the press for the accord 5th gear, it didn't pop or anything, just slid out. I was actually able to remove 3rd gear by hand.

Differences for the 3rd/4th synchro hub. Both are 34 spline with the same OD though.

5th gear synchro hub splines are different length/positions too.



4th/5th spacer collars are the same


Showing the differences in the mainshaft. 3rd/4th synchro hub on accord mainshaft, all the way on.

Accord 3rd/4th hub on prelude mainshaft.



Prelude 5th gear spacer collar, 37mm

Accord 5th gear spacer collar, also 37mm


Took a file to 5th gear, you were right 94EG8 it was soft

Filed 4th too, much better but was still able to make a few scratches.

Tried 3rd, barely left a mark.

Not the most scientific I know since I tried it in all different spots but better than nothing.

Ran out of time today, I re-assembled both trans with out the mainshafts so I can take them home and spend some more time figuring out what I can cook up.

Oh, didn't take any pics but I can't put the LSD into the Accord trans, Accord ring gear is 10 bolts while Prelude is 14 bolts.

2rare.2find

Hi guys I also had a problem with my m2b4. i have a 96 accord with a f20b swap . i had to change my passenger side axle and i put in a stock accord axle. when i turn to the right there is alot of vibrations and when i turn left it drives really smooth. did i put in the right axle? i think the previous owner mightve put in the prelude axle in but i dont know weather it was a 4th gen or 5th gen lude axle.. i wouldve made a thread but im a new user so i cant do that yet. if anyone can help me that would be amazing. pm me thanks