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m40 made some noises. Then made some worse noises. Then maybe blew up?

oemoilleaks

Member
Joined
Mar 26, 2017
Location
SoCAL
I finally got my new engine (big bore b20) in the car, the cam broken in, and decided to take it for some quick break in miles. I made it about 15 miles before I turned right, to head into Las Flores canyon in Malibu.

I made it about 1000ft. before it made a big bang and I started hearing some rattles. I immediately got under the car to find some oil leaking off the speedometer cable support. It looked like some oil coming out of the rear main seal and wasn't enough to make me really worry. So I decided to turn around and nurse the car home. The noises went away as I slowly approached 60mph. Still I was headed straight toward the garage.

As I pulled off, I downshifted into 3rd, and the noises appeared again. Only this time they stayed long enough for me to actually listen. The first three gears were whining, almost as if I had straight cut gears in there.

Then I noticed the pilot bearing making a noise. As soon as I disengaged the clutch it would go away, release the clutch pedal and it was back. I made it two more blocks before I lost the ability to get into 1st. I turned the car off, put it in first, and tried again. As soon as I shifted into 2nd, it went BOOM! I looked under the car to find a BUNCH of black oil (not the brand new oil from the engine which is actually green) covering the midsection of the car.

We flat-towed it the 6 blocks back to the garage, slammed it into reverse, and willed it into the garage where it now sits on stands.

Any clue where I should start looking? I know the transmission needs to come out, and that it's internals are probably shot (haven't drained what's left of the fluid yet but I have a feeling there's gonna be chunks). I don't understand gear boxes or know really what I'm looking at.

Should I be looking to replace it?
A friend offered me a complete m410 but I don't know if that'll fit in a '68 142s.

Should I just do the t5 swap now that I have to replace the transmission?

I have no idea what I'm doing
 
The M410 will not work, unless it's a unicorn from an 1800. And those are 1 year only gearboxes.
If you are wanting to keep it close to original, you may be looking at a full gearbox rebuild. It's not overly difficult, but if you've never done one it might be better to have it done. Hiperformance Auto in Torrence, CA are the recommended "go to" guys.
If you aren't planning to keep it looking original and are going for more performance (which it sounds like you are with the big bore B20), then going with a T5 swap may suit your needs better.
 
Yes I know about HiPerformance. Eric and Ian are great guys who've helped me on many occasion.

Why won't the M410 work?
 
Unless it's out of a '70 1800E the bell housing, input shaft and front seal housing on a M410 are larger for the B30 engine/clutch.

Your M40 trans is toast. There are likely very few salvageable parts.

Later versions of the M40/M41 are stronger but still won't handle much abuse with a built B20.
 
Can you get a picture of the M410? You might get lucky.

My buddy said he'll send me some photos when he gets back from Italy.

Judging by the conversations we've had about it in the past, I don't think it's going to be the unicorn 1970 p1800 one I'm hoping it is.
 
Unless it's out of a '70 1800E the bell housing, input shaft and front seal housing on a M410 are larger for the B30 engine/clutch.

Your M40 trans is toast. There are likely very few salvageable parts.

Later versions of the M40/M41 are stronger but still won't handle much abuse with a built B20.

This is what I needed to know. Bullocks.

Looks like we are a go for t5.

Has anyone successfully put an s10 t5 in and been able to keep the school is shifter?
 
I don't think so. But you can install 1 of these if you are going to install a T5. Cutting is required!!

FYI, we have them in stock.

TunnelCover.jpg


1 of the advantages to the M410 is it is a bolt in IF you have all the right parts. And you can use your old shift cover so you keep your old school shifter.

BTW, we have all of the important needed installation parts like the special transmission crossmember. We also have all of the needed parts to rebuild an M410.
 
I don't think so. But you can install 1 of these if you are going to install a T5. Cutting is required!!

FYI, we have them in stock.

TunnelCover.jpg


1 of the advantages to the M410 is it is a bolt in IF you have all the right parts. And you can use your old shift cover so you keep your old school shifter.

BTW, we have all of the important needed installation parts like the special transmission crossmember. We also have all of the needed parts to rebuild an M410.

Good to know! I was going to bring it by to have the u-joints done but this happened on the literal first test drive miles so I don?t think it would have made it.

I?ve been wanting to put a t5 in for a while. I already have the s10 t5. Which has the shifter more forward than usual world class one everyone goes to. If my calculations are correct (which they rarely are) the shifter should only be about an inch or so further back from the stock location... which should only require making the tunnel hole a little larger. It should fit in the tunnel without modification. Again, my calculations aren?t always right.

He?s going to give me a really good price on the M410 so that may be the easiest option if you have all the parts I might need.

But having a true fifth gear is very tempting
 
Does anyone have the measurements of an m40 and an m41?

Looking for the overall measurement of the m41 from the bellhousing to the prop shaft.
And I need to know the measurement on an m40/m41 from the front of the actual gear box to the shifter (schoolbus style)
 
If you're trying to figure out if the shifter on the S10 T5 shifter is going to line up with the hole in the tunnel, it won't. We've already been over this.

The stock shifter hole is 12?" from the bell housing to block mating surface. The S10 tail housing puts the shifter 11?" from the bell housing to transmission mounting face. That only leaves 1?" for the M45/6/7 bell housing and the adapter plate. I don't think you're going to be able to make the T5/S10 shifter line up with the stock hole in the floor board.

1053558.jpg
 
If you're trying to figure out if the shifter on the S10 T5 shifter is going to line up with the hole in the tunnel, it won't. We've already been over this.

I?m not trying to figure out IF it will line up. I?m trying to figure out how far off it is.
 
I'll measure a M46 bell housing and T5 adapter plate for you tomorrow.

Thank you! And thanks for posting that response from your brother.. SOOO Much has happened since I asked that question initially that I honestly forgot about the ENTIRE thread.
 
Stock shifter location is 12.75" from the mating surface
S10 t5 is 18.145" from the mating surface

Which is a shift toward the rear of 5.395"

Looks like the m410 is looking more likely.
 
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