Identifying early Holden four speed gearboxs. M20, M21. Aussie 4 speed.

A quick look at identifying the Holden Aussie four speed M20 and M21 gearbox.

[@steelcitycaprice.899]

👍🏾😎 100% Crystal clear 👏🏾👏🏾👏🏾 I picked one up from a relative and i dont know which it is but at least now i can go outside and check much thanks to this post.👍🏾

[@robbieninja]

you forgot the xu1 box. an M21 with a different 3rd ratio, and input 6 cylinder input shaft. I converted to a V8 ratio by changing the cluster and 3rd idler gear keeping the 6 cylinder input. much better and evenly spread ratios for competition back then. Good video.

[@Hitman-ds1ei]

The missing piece this is the early production boxes used a retaining nut on front bearing that doubled as a slinger like the muncie, no lip seal until into HQ model mid 71 ish i believe but probably different from assembly plant to assembly plant, therefore front bearing retainer different and also numbers for shafts and cluster, 3 spd same deal

[@RagingRangaaa84]

Exactly what I was looking for. Thanks mate appreciate it 👍🏻👍🏻👍🏻👍🏻

[@JosephCowen-fz8vj]

I once had a smooth case holden 4 speed , the case was exactly the same except no ribs on it ! Ive had many many holden 4 speeds and never saw that before ! No it wasnt a saginaw ir muncie , it was a holden , i thought the case might have started out as a 3 speed , and someone stuffed 4 speed internals and output housing on it . I wish i still had a pic of it . I also had a factory HT V8 3 speed , it was 3 on the tree V8 box . But you are rite about the M22 , i had a HJ one tonner 202 4 speed M22 and 4.44 lsd sailsbury diff , 1 st was useless , even 2 nd only got you 30 kmh max .

[@marco3499]

Hi. According to Factory Workshop parts manual. Spot on :). I have one. And like you said. The grooves in input shaft are not 100%. My input shaft has only the 1 groove. Good stuff :)

[@StreetspecTV]

Thanks for the feedback 👍

[@JimmyJohnson7077]

​@@StreetspecTVhi mate is it possible to only change the 6 cylinder imput shaft for a v8 one or is there more too it than that?

[@alandawson1197]

what about the opel 4 speed

[@stevenbradford1662]

Great explanation. Can you bolt an M20 6 cylinder gearbox onto a HK 186 standard 3 speed bell housing?

[@StreetspecTV]

Thanks for the feedback. Yes, the gearbox will bolt to your bellhousing. Make sure you check out my other videos. 👍

[@stevenbradford1662]

@@StreetspecTVthanks for the reply, appreciated. Great, so I will be able to retain the hydraulic clutch system.

[@Ninja_Kenny]

I have a M21 behind a 5ltr WB 1Tonner. It keeps throwing 3rd gear out after gaining a few rev's, is it the scyro's ... my mate says it's adjustment, I have adjusted it with no joy.... synro's right ? Only does it in 3rd....🤔

[@StreetspecTV]

@Ninja_Kenny syncros help you go INTO gear, NOT out of gear. Worn dog teeth on 3rd gear most likely. excessive end float due to worn thrust bearings can cause them to jump out if gear as well. Either way is tear down and rebuild.

[@Ninja_Kenny]

​@@StreetspecTV Thankyou so much for the fast response, agreed rebuild when money permits, until then ol Ethel is a 3 speed 😅

[@claudeciccotelli2661]

i was sure the aussie 6 m20 had a 1.51 third gear ratio not a 1.15 shown on your vid

[@StreetspecTV]

You are correct, typo on my part.

[@V8TriHQWagon]

Thanks

[@darrenmurray4580]

Hey .. is there drain plugs on these models. I have a had a good crawl around and cant locate. Can you drain these. I have a WB 253 I am restoring . Cheers

[@StreetspecTV]

Hi, thanks for watching. Yes, these gearboxes do have a drain plug. It is the very bottom extension housing bolt. You should notice it will have copper washer or similar. Remove this bolt and you can drain the box. Re-fill via the large plug about half way up the case on the opposite side of the linkages. Make sure you check out my other video's 👍

[@bradgray8064]

Well explained. Cheers

[@user-uw1xs3gl6c]

Hi. I've got an 743 input shaft. Any idea what this is from? No grooves

[@rodneybrown4951]

My 4 speed has a very high first gear which does 80 ks per hr. I am not certain if it is an m20 or 21? can someone help?

[@StreetspecTV]

Hi,thanks for watching. By the sound of it I'd say you will have a diff with very tall gearing fitted. It will have the ratio stamped on the front flange of the diff, just behind the uni joint, sounds like it will be 2.78 or lower.

[@rodneybrown4951]

@@StreetspecTV 3.08

[@plumquick1]

had an ux1 close ratio box 80 Kay's first gear great for long patches in first

[@shananroberts6678]

Hey there I have a box I think to be a m20 but it has no groove on the input shaft, would you know what that box is?

[@StreetspecTV]

Hi, thanks for watching. It's most likely had a aftermarket input shaft installed. Check the part number stamped on it, that should tell you. You'll have to remove the front bearing retainer to see it. Or put it in first gear and count the number of turns of the input shaft for one turn of the output shaft. 2.5 For m21, 3 for m20. Cheers.

[@brettsosich8588]

I'm trying to determine if mine is 6 or 8 cyl. On mine from the face where bell/h bolts to and the tip of the input shaft is about 169mm. What are the measurements for the two shafts off the face Cheers

[@StreetspecTV]

Hi, thanks for watching, 169mm from front of gear box to the end of the input shaft is a 6cyl box.

[@brettsosich8588]

@@StreetspecTV cheers

[@bobburns7277]

Aussie 4 Speed Boxes are made of cheese