Mine whines pretty bad, but its a combo of rear diff and tranny. Its wearing out. Rebuild would probably help, I'm swappin in a 4spd. Theres not a 3 spd out there thats less than 30 years old, most have at least 100k on them.
The three speed transfer will work on a four speed with an adaptive gear and bearing. The four speed output shaft is fatter(new bearing required) and 16 spline instead of 10(thus the new gear). A 47-67 gm sm420 four speed will bolt to the three speed bellhouse...a spaceghost plate adapter gets your transfer onto the 420, classic cruiser or wardens make nosecone adapters for you throwout and pilot bearing. Either way is a nice upgrade. Stock toyota three speed: 2.5 to 1 first. Toyota 4 speed: 3.5 to 1 first. Toyota h41 four speed: 4.9 to 1 first...sm420: 7 to 1 first...
Speaking of throwout bearings, how often do you guys see these cause a whine? I seem to have a similar high-pitched rub/whine after rebuilding both tranny and transfer case. Comes and goes with putting the clutch out and in, and changes with engine speed. Also, seems to be affected by hitting bumps in the road.
I have the same problem on my 73. I only notice it in 3rd gear over 45mph. I have only been able to get up to 60mph, because the noise gets too loud. I am probably going to pull my tranny out in a few weeks and take a look at everything and see what is going on. Let me know if you find out something before I do, and I will do the same for you.
Go to tech, read all the writeups there. Heres the quick n dirty:
SM420-GM 4 spd 1/2 to 2 1/2 ton trucks/vans. '47 to '67. Later years are better because they don't spray oil on the clutch at steep descents. The big plus is the 7.05 : 1 first gear, first gear is not syncronized, and will in all but extenuating circumstances not used on road, think of it as a toy 3 spd with a syncroed first gear and a granny gear only for crawling. So its road manners are marginally better than the 3 spd because of the syncroed first.
Requires toy 3spd bellhousing to bolt to either F or 2F
(SO far only part of conversion I'm not clear on is the clutch setup)
Adapter used to bolt to transfer. Simplest, most inexpensive and hence best is probably SG's plate adapter.  oesn't necessarily need driveshaft length change-I'm not sure on this and it doesn't matter for me cause I need new/retubed shafts anyway cause the front is dented bad.
Thats the basic info. I was orignally planning on a toy 4 spd conversion, but then heard about this one, realized its not much more difficult, almost cheaper, and gets a first gear thats twice as low. I could throw 3.70's in the diffs and have a solid 75 mph highway speed and still have a better granny than I have now, with the ability to run as large of tires as I could want too with a 4" lift. Its a beautiful transmission perfectly suited to my needs.
Now you need to decide if its the one for you.
$125 for SG adapter
~$100 for tranny itself
$130 for rebuild kit (seals, bearings, 3rd 4th syncros)
Set aside another oh lets say $100 for misc. parts, hardware and tools.
Oh yeah either buy an AA twin stick T-case shifter (what I will do) or build your own. (not an option for me cause I can't weld)
Because the SM420 w/ adapter is a different length than the stock setup, so your transfer case shift linkage will no longer work. The AA one is length adjustable, making it the easy choice for us welder-less cruiserheads.
when are you going to put yours in? are you going to make a write up for the rest of us?
i'm in the process of hunting down a 420. i've got a friend with more spare engines and transmissions sitting around then he knows what to do with. i'm hoping he can get one for me. he's also connected with everyone motorhead in the county, so hopefully things will work out.
I am starting to collect parts now. Hopefully meeting SG in Tellico later this month to buy the adapter in person, and making calls to junkyards to see if they have any '60 to '67 GM 1/2 to 2.5 ton trucks sittin around. :G
As soon as I get the tranny I will rebuild it, and then make sure I have all the parts, then take out the seats, gas tank, gas tank cover, and tranny hump and tow it out to a friends 8,000 sq ft shop, where I will spend a day actually bolting the tranny in and all. ETC is end of July.
I might do another writeup, I don't really see a point considering how complete Pin_Head's is. Normally when I start on a project I'm in too big a hurry and focusing too hard on the project to take time to take pictures and such. :dunno: