Have an 85 VK Holden SS which has an M21 4 speed in her.Recently purchased what I thought was a second hand M21 but has actually turned out to be a M20.Would anyone know if I can just swap the longer v8 input shaft into the M20!I know the gear ratios are going to be different,really just need to know if any other parts need swapping over/buying.
edangus,
Jan 5, 8:00am
I wouldnae be putting an M20 behind an 8. But thats just me.
kaysum2,
Jan 5, 8:04am
It was not the original plan to, but am stuck with this box now, have already pulled out the m21, am very open to any other suggestions.
edangus,
Jan 5, 8:08am
Can you get ya M21 rebuilt or is it super poked!
It will end in tears if you put the M20 in.
richard198,
Jan 5, 8:10am
I thought you were talking about BSA M21 and M20 motorcycles!
kaysum2,
Jan 5, 8:12am
Pretty much all the gears are noisy now in the M21 which was my reason for replacing, am pretty pissed at the guy that sold it to me, sent up from wellington, to find it was not the right one even tho he stated it was.
kaysum2,
Jan 5, 8:13am
Nope.good old Holden :)
treachug,
Jan 5, 8:16am
M20 is 3.05:1 first gear & M21 is 2.54:1 first gear. Can be found in both 6 & 8 cyl. So you bought a box thinking it was an 8 box (sold to you as an 8cyl box) & found input shaft is shorter making it a 6 cyl box!
treachug,
Jan 5, 8:19am
What is the part number on the cluster gear on the box you want to use & the cluster gear of the box you want to replace! Can be seen easy as when looking at cluster
edangus,
Jan 5, 8:20am
You can tutu with it. Jump on one of Holden Forums, will send you down the right path of what needs changing.
Personally I would rebuild the M21.
kaysum2,
Jan 5, 8:24am
Yip bought it as an 8 box.Cluster gear on the orignal box is 2813497 and on the replacement one ends in 496, which according to google is for the 6.
wellabolla,
Jan 5, 8:24am
i have a celica 5spd with a chev bellhousing i want rid of.much nicer than the dirty old munchy.lol.
kaysum2,
Jan 5, 8:27am
hmm thanks, may consider it, was wanting to keep her in original condition as it is a genuine HDT VK SS
treachug,
Jan 5, 8:30am
Yep, .497 is M21 & .496 is M20 - so no, cannot be swapped. If was same number then yes can be done but in your case.its a negative that!
kaysum2,
Jan 5, 8:36am
Crud.spent $1000 for the gearbox inclu delivery.Am so gutted and feel so ripped!
edangus,
Jan 5, 8:41am
Sell it. May even find a gearbox shop who will swap it as part payment for a rebuild.
treachug,
Jan 5, 8:41am
wow, I would go back to him & tell him its not what he sold it as. Try to get a refund. What gears in your old one need replacing!
patiki1,
Jan 5, 8:45am
Give Performance Transmission a ring.
kaysum2,
Jan 5, 8:46am
He is in wellington, have txted and said thats it is not an M21, his reply was he brought it as an M21, and hopes not to much of a c*#t around getting it in!Third gear is defnitatley the worse, 1st and 2nd starting to get noisy. So the three gears that are different ratios between the 2 boxes
kaysum2,
Jan 5, 8:47am
will try them in the morning, cheers
shorty11,
Jan 5, 8:55am
this guy in pukekohe will help you.he specializes in muncie g.boxes.09 2383832;derek .he on to it
treachug,
Jan 5, 9:10am
Will check in morning at work & see what new gears we can supply/get.
kaysum2,
Jan 5, 9:12am
wow thanks heaps ! This might sound stupid but is it possible to swap the input shaft and the first cluster shaft (sorry wife asking the questions here) to fit into the v8 shaft, will the rest line up!
kaysum2,
Jan 5, 9:14am
awesome thank you so much,l will call him in the morning.hopefully not going to cost too much more!*imagining how many shoes I could have brought with $1000* (wife of dissapointed husband)
treachug,
Jan 5, 9:15am
1St gear, 2nd gear same in both M20 & M21, 3rds the killer as well as the input shaft
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