strange M46 behavior

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James Sweet - 07 Jul 2006 07:36 GMT

The M46 tranny in my 242T has been acting up lately. The odd thing is
that sometimes it's perfectly fine, other times it doesn't like to go
into 1st at a stop and I have to jam it in. Sometimes if I try to
downshift into 2nd or 1st while the car is still moving it glides right
into gear, other times it grinds and goes "ker-chunk" as it engages. The
clutch is fully disengaging, I'm positive of it, 3rd 4th, and reverse
gears work perfectly 100% of the time, this is something internal.

I have another gearbox I could swap in but I don't really feel like
doing that yet if I don't have to. Any idea what's actually going on
internally?

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Mike F - 07 Jul 2006 13:09 GMT

> The M46 tranny in my 242T has been acting up lately. The odd thing is
> that sometimes it's perfectly fine, other times it doesn't like to go
[quoted text clipped - 7 lines]
> doing that yet if I don't have to. Any idea what's actually going on
> internally?

I had this in my '83 turbo. A snap ring that retains the 1-2 hub in
place on the main shaft has broken. The gears hold each other in place
pretty much, but now two surfaces are rubbing together that are not
designed to. They will wear each other out and this problem will get
worse. As I remember, when you're in second gear, the side load caused
by the angle cut of the gears forces the 1-2 hub rearwards, this load is
taken up by the forward surface of first gear.

This is a common problem - the replacement snap ring is 2 mm thick, as
opposed to the 1.75 mm of the original - they say this makes all the
difference!

Signature

Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

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James Sweet - 08 Jul 2006 03:15 GMT

>>The M46 tranny in my 242T has been acting up lately. The odd thing is
>>that sometimes it's perfectly fine, other times it doesn't like to go
[quoted text clipped - 19 lines]
> opposed to the 1.75 mm of the original - they say this makes all the
> difference!

Wow, I bet you're exactly right! I did notice the shifter seems to move
backward slightly when I accelerate in 2nd, something I didn't notice
happening with my other M46 equipped car.

I suppose I should prep the new tranny to go in sometime this summer. It
goes along with my plan to swap the rear axle with a later one
incorporating the speedo sensor and installing a later year electronic
speedo since the replacement M46 lacks the speedo drive and I'd like to
go electronic anyway.

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Mike F - 10 Jul 2006 13:39 GMT

> >>The M46 tranny in my 242T has been acting up lately. The odd thing is
> >>that sometimes it's perfectly fine, other times it doesn't like to go
[quoted text clipped - 29 lines]
> speedo since the replacement M46 lacks the speedo drive and I'd like to
> go electronic anyway.

In the meantime, minimize the use of 2nd gear. It's too bad that the
failure of a $2 part (from Volvo, 10 cents elsewhere) causes 2 $500
parts to destroy themselves.

Of course, you could always swap the overdrives to get the speedo gear.
As I'm sure you know, it's not too hard to pull the overdrive unit off
under the car if you want to change it later.

Signature

Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

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James Sweet - 11 Jul 2006 03:03 GMT

> In the meantime, minimize the use of 2nd gear. It's too bad that the
> failure of a $2 part (from Volvo, 10 cents elsewhere) causes 2 $500
[quoted text clipped - 3 lines]
> As I'm sure you know, it's not too hard to pull the overdrive unit off
> under the car if you want to change it later.

Yeah I've done that before.

I knew there was another reason I hadn't gotten to this yet, well
actually two. First, the OD I have has a shot output bushing, the second
is that the new tranny is from a 700 and setup for a hydraulic clutch. I
have a master clutch cylinder I found in a manual 264, but I should put
a new seal in it. I also need to figure out the plumbing and find the
slave cylinder which I left at a friend's place and it got buried in the
garage.

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