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LH traumatic -> m21?

Started by _oikurtman_ , Aug 21 2006 01:23 PM

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35 replies to this topic

#1 _oikurtman_

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Posted 21 August 2006 - 01:23 PM

i know this has been asked a thousand times before but i've heard a lot of different answers...

thinking of swapping the trimatic for a 4 speed behind my 253.

What's the difference between an m20 and an m21?
Is the hole in the tunnel the same?
Will a 6cyl ratrap style clutch pedal fit the v8 cable setup?
They're the same length aren't they? no tailshaft mods needed?
Is the cross member the same?
Have to swap the flex plate for a flywheel right?
What's the go with the 'spigot?' i'm not sure what it even is exactly.
Anything else i should know?

I know there's a lot of questions :rolleyes:

Cheers.

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#2 _oikurtman_

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Posted 22 August 2006 - 12:28 PM

Anyone?

I know at least a few of you must have done this job before!

Cheers.

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#3 _flukey77_

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Posted 22 August 2006 - 02:23 PM

I'm planning the same swap, behind my 192. Apparently the tailshaft is the same. And yeh, you will need a flywheel to replace the drive plate. They are similar except that the flywheel is a stackload heavier to make up for the weight difference between the torque converter and clutch. The spigot is a bush that sits recessed into the end of the crackshaft. The manual one is different from the auto one. Someone on this site told me that you can get them cheap from your local holden dealer, though I havent tried this out personally. Not sure about the rest sorry. Im still learning some of that myself.

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#4 MRLXSS

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Posted 22 August 2006 - 03:50 PM

i know this has been asked a thousand times before but i've heard a lot of different answers...

thinking of swapping the trimatic for a 4 speed behind my 253.

What's the difference between an m20 and an m21?
Is the hole in the tunnel the same?
Will a 6cyl ratrap style clutch pedal fit the v8 cable setup?
They're the same length aren't they? no tailshaft mods needed?
Is the cross member the same?
Have to swap the flex plate for a flywheel right?
What's the go with the 'spigot?' i'm not sure what it even is exactly.
Anything else i should know?

I know there's a lot of questions

Cheers.

Ok, ill try and answer your questions..

M21 has a shorter first gear i believe, so it takes off harder...

The Hole in the Tunnel is identical!

Yes the 6cyl rat trap set up works! i use it in mine!

Yes they are the same lengths, you can even still use your 6 cyl tailshaft

Cross member is the same!

Yes, u will need to get a Fly Wheel, and also you MUST buy a spigot bush to put on the inside of the flywheel so the end of the input shaft stays in position

The spigot bush is just a pourus (ceramic?) cylinder, with a hole in the middle of it, it just really holds the end of the input shaft so it stays square and doesnt break stuff! Remember to soak it in oil first!

Umm wat else....

Selectors are the same....

eerrrr nothing else i can think of right now....

good luck!

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#5 _J&S Racing_

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Posted 22 August 2006 - 05:02 PM

The spigot bush is brass there about $7 at repco and as 253ToranaSS said soak it in oil first. They have pritty much answered the rest.

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#6 _oikurtman_

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Posted 23 August 2006 - 10:03 AM

Thanks guys. Very much appreciated.

So when buying an M21, I have heard of people wanting to know the cluster gear number. Why so? :huh:

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#7 makka

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Posted 23 August 2006 - 04:06 PM

thats to identify it from a M20. just so you know, the M21's are no stronger than a M20, but they cost more. whick one is better for you really depends on your rear end gearing

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#8 DanWA

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Posted 23 August 2006 - 04:13 PM

the traumatic with a proper shifter and a shift kit and or stall would shit all over a manual though, you also get better fuel economy from auto to, someone correct me if im wrong

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#9 _oikurtman_

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Posted 24 August 2006 - 08:57 AM

i run a pretty much standard blue 253 with extractors and dual 2 inch exhaust, standard trimatic and soon a 3.08 diff (not sure what i have now, feels like 3.36 though).

So a v8 M20 is no stronger than an M21? Just different ratios?

Later on i plan to put the 308 in. Would either box be ok for that?

Cheers.

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#10 Dr Terry

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Posted 24 August 2006 - 10:12 AM

Hi Guys.

253Torana SS said "M21 has a shorter first gear i believe, so it takes off harder..."

No, that's not correct, the M21's 1st gear is taller & doesn't take off as well. If you also run a tall diff (2.78 or 3.08) it pulls the s#*t out of the clutch on launch.

IMO the M20 has a better set of ratios for suburban traffic, especially if you see a lot of traffic lights. The M21 is 'close ratio' box & is more suited to high speed driving where you need 3rd to be closer the 4th. There is no difference in strength between any of the Aussie 4-speed regardless of their ratios.

Dr Terry.

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#11 MRLXSS

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Posted 24 August 2006 - 11:04 AM

ok, i knew it was either one way or the other.... Thanks for clearing that up!

Might also explain why car car is so shit to launch with the 3.08 diff!

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#12 _oikurtman_

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Posted 25 August 2006 - 06:46 PM

i do a lot of city driving. some highway, but 4th is still the same right?

i also run a 2.78 diff, soon to be a 3.08. So an M20 would be a better option right?

My only worry is that i plan to swap to 308 eventually. But i haven't seen any 308 M20 setups. I've only seen 308 M21 drivelines. Would the M20 hack it?

Cheers.

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#13 _MAWLER_

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Posted 25 August 2006 - 08:51 PM

From I know (rumour, innuendo and guesswork) the M21 was what the 308 came attached to. The theory being the extra torque etc would cover for the doughy 1st gearing and that.

I much prefer the M20 (mind its like comparing sushi and sushini, they're both crap) because of the lower gearing. Had a mate who swapped the M20 in his 308 torana for the M21 and he regretted it every damn day, more sluggish. As for the higher gears/highway can't help.

JMO

Cheers,

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#14 _UCV80_

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Posted 27 August 2006 - 03:42 AM

i thought u cant run an m20 in v8?

the imput shafts are different lenths, if u got a v8 and want manual, u *need* m21

correct me if im wrong
:tease:

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#15 TerrA LX

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Posted 27 August 2006 - 03:57 AM

M20 came in 6cyl and V8 versions with different input shafts to suite.
if you going to spend money either get the tri tricked or go at least a toyota box or similar.
IMHO aussie 4 speed is crap.

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#16 makka

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Posted 27 August 2006 - 10:02 AM

M20 came in 6cyl and V8 versions with different input shafts to suite.
if you going to spend money either get the tri tricked or go at least a toyota box or similar.
IMHO aussie 4 speed is crap.

just the same as you can get a 6 cyl M21.......

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#17 _flukey77_

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Posted 27 August 2006 - 05:41 PM

This site has some interesting info if you are interested, ratios and casting numbers and all.

http://www.5speeds.com/muncie2.htm

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#18 Dr Terry

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Posted 28 August 2006 - 07:11 AM

Hi flukey77.

That website is all about US Muncie gearboxes, nothing to do with Aussie 4-speeds.

The only commonality is the use of the PO numbers M20/M21/M22.

As I have mentioned several times before, these are only option numbers they are not identifiers. The HR-HG/LC Opel was an M20, a Gemini 4-speed was an M20, the HK-HG Saginaws were typed M21 or M22. So don't make the same mistake as the guys at Street Machine magazine & confuse US boxes with ours.

Dr Terry.

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#19 _oikurtman_

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Posted 29 August 2006 - 01:26 PM

Wasn't the M20 v8 only for 253's though? Liam, did your mate with the 308 and M20 ever have any problems?

The gearing sounds as though M20 would be best for me, correct me if i'm wrong. Just wanna know if it will last.

Why does everyone always mention toyota boxes when talking about aussie 4's? :huh:

Easy conversion?

Cheers.

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#20 makka

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Posted 29 August 2006 - 01:36 PM

Wasn't the M20 v8 only for 253's though? Liam, did your mate with the 308 and M20 ever have any problems?

they are the same strength! there is no difference other than ratios!!

Edited by makka, 29 August 2006 - 01:36 PM.

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#21 _oikurtman_

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Posted 29 August 2006 - 03:34 PM

Cheers Makka.

So the M20 ratios would be better suited to city driving with a 2.78/3.08 diff?

Do both rat trap and cable clutches fit v8 bellhousings? what are the pros and cons?

Cheers.

Edited by oikurtman, 29 August 2006 - 03:37 PM.

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#22 makka

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Posted 29 August 2006 - 06:39 PM

yes, the ratio's are better for what you want, dunno bout the clutches, but I would assume so.

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#23 MRLXSS

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Posted 30 August 2006 - 01:05 PM

No, i beleive they are different bell housings, as the rat trap style pushes the fork and the cable version pushes the fork... I remember looking into this when my clutch rod snapped...