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Manual transmission question

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gregsenne

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Im in the process of building my truck, and I took my SM465 transmission apart to see what it looked like inside. The transmission is the 3 speed with granny out of a 79 1 ton truck. When I got the transmission it didn't have any fluid in it because the guy said he drained it. It shifted well and spinned as expected. I took the top cover off and everything looked great inside, so I filled it to the right amount of fluid with 80w90, changed the seal on the input shaft bearing retainer, and put the top cover back on and bolted the np205 up. Then I noticed the input shaft difficult to turn, and the output shaft sometimes spinning when in neutral. Sometimes shifting to certain gears will lock the entire transmission. So I took top cover back off, and the problem still exists. It happens on both shift forks, and it seems like the gold rings get stuck. I'm not 100% sure everything I'm looking at inside the transmission, and I didn't take any gears out or mess with anything inside of it besides moving the shifters into and out of gears by hand. If I move them by hand now with the top cover back off, still having the problem.
Also, I know the 80w90 oil is thick, but it is incredibly harder to turn with fluid in it. If I grab the input shaft and spin in a few times around, my hands hurt from gripping it so hard (if that gives you an idea of how hard it is).
Thanks for any ideas. This is my first time looking inside a manual transmission.
 
The input shaft is very small, you're fighting the friction of the oil on all the surfaces and synchros. Grab an old clutch disk and use that to spin the input shaft while you shift into all the gears to verify its working correctly.

Once the oil starts flowing and gets upto temp it will spin much more smoothly. My Ford NP435 was tight like that after a new rebuild with fresh synchros and bearings.
 
the output shaft will spin a little in neutral from the fluid friction of the gear oil moving around. I had 85w140 in mine and on cold mornings the truck would actually move foward in neutral and also shifted really rough until it warmed up. Basically the heavier the oil, the worse the affects. 80w90 is ideal so its not too thick. For one winter I put in 50w oil and it made the transmission shift much better while cold but being that light I also avoided prolonged heavy use that would heat up the transmission (like towing.)
 
Thanks for the replies. That makes sense that the thick oil is preventing it from spinning easily. However, I still think there is a problem with the gears not coming disengaged when shifting out of them. The biggest indicator to me is that I will occasionally shift into a gear and shift back out of it. When I go to shift into a different gear, it will lock the entire transmission (as if I was in 2 gears at once). Shifting in and out and in and out and in and out of different gears will get it back the way it should be, but it doesn't seem right that it should do this. This happens with the top cover on and with the cover off.
I know you said the output shaft will spin a little in neutral, and before I took anything apart, I noticed this. However, if I took a screwdriver and held it against one of the teeth in the output shaft, I could turn the input shaft and hold the output shaft in place. I cannot do this anymore.
I've never ran this transmission, yet. It's still sitting on the garage floor, and I want to figure out what is going on first before I install it, I'm afraid if I run it and it gets stuck in 2 gears at once, and connected to the engine, it will destroy the transmission.
 
A-Synthetic

B-Are you running the correct gear oil? GL5 is for differentials and is NOT friendly to the brass/bronze synchros in manual transmissions. Someone put that in my buddy's Jeep's NV3500 and my Tracker's Aisin manual trans and both have/had shifting issues. Actually killed his NV3500. GL4 is what you want in a manual transmission unless it's spec'd otherwise.
I put Synchromesh in mine a year ago but have four quarts of Redline MT90 waiting for it on my work bench.
 
I know you said the output shaft will spin a little in neutral, and before I took anything apart, I noticed this. However, if I took a screwdriver and held it against one of the teeth in the output shaft, I could turn the input shaft and hold the output shaft in place. I cannot do this anymore.
Click to expand...

Take your top cover off again. You'll see three collars inside which is how the different gears are engaged or released. The shift forks slide the collar either forward or back. For the tranny to be in neutral the first two collars need to be centered and the last collar must be all the way back. At that point you should be able to turn the input shaft pretty easily and hold the output shaft from turning.

To re-install the top cover correctly you need to begin with the tranny itself. The last collar is the reverse collar. Slide it forward so it is halfway engaged. Put your shifter in the top cover and use the shifter to find "halfway" into reverse. Carefully lower the top cover onto the tranny while watching that forks and collars align properly. This might take a few tries, but it is the only way to successfully re-install the top cover.

Use an old clutch disc to turn the input while trying every gear including reverse. Watch the output...
 
AJMBLAZER said:
Are you running the correct gear oil?
Click to expand...
I thought so. I looked around on the internet and it seemed most people were using 80w90 gear oil in this transmission.



tRustyK5 said:
Take your top cover off again. You'll see three collars inside which is how the different gears are engaged or released. The shift forks slide the collar either forward or back. For the tranny to be in neutral the first two collars need to be centered and the last collar must be all the way back. At that point you should be able to turn the input shaft pretty easily and hold the output shaft from turning.

To re-install the top cover correctly you need to begin with the tranny itself. The last collar is the reverse collar. Slide it forward so it is halfway engaged. Put your shifter in the top cover and use the shifter to find "halfway" into reverse. Carefully lower the top cover onto the tranny while watching that forks and collars align properly. This might take a few tries, but it is the only way to successfully re-install the top cover.

Use an old clutch disc to turn the input while trying every gear including reverse. Watch the output...
Click to expand...
This is exactly how I did it the first time. I just took it off and put it back on again, and same thing. I haven't got it to lock up yet as it did yesterday, but the output shaft still spins in neutral. Putting it in ANY gear makes the output shaft spin appropriately for that gear, even reverse. Then, when you shift to neutral, the output shaft feels like it is in 3rd gear (judging by the amount the output shaft rotated in 3rd gear compared to neutral).
The gears do seem to be harder to get into now than before I took it apart. They used to slide right in each gear (without the fluid), and now I sometimes have to move them back and forth and turn the input shaft to get them into the gear.

Thanks for all the help.
 
If it makes any difference.... When I took the front bearing retainer off (the round cover that goes over the input shaft) to replace the front seal, I rotated the input shaft with the cover off. It made the input shaft slide out a bit (but didn't fall out of the transmission). Carefully turning it when putting it back in seemed to make everything line up.
The input shaft never came more than 1/2" out.
It worries me tho because it feels like it's in 3rd gear in neutral, and 3rd gear is the closest gear to the input shaft.
Could this have screwed anything up?
Thanks.
 
I'm no expert but I would believe a 1/2" of play in the input shaft is no good :eek1:
 
no a 1/2'' of play on the front of a sm465 is normal because the input shaft isnt connected to the mainshaft of the trans so it will slide out alittle bit, there are some roller bearings on the inside of it but i dont thnk they can fall out unless the input shaft is all the way out. the only way it will come all the way out is if you drop the counter shaft to make room for the gears to clear.

Now if you have your front bearing retainer on and you still have a 1/2'' of play you might have a issue but i dont think you could unless somethinking was pretty broke.
 
gregsenne said:
I thought so. I looked around on the internet and it seemed most people were using 80w90 gear oil in this transmission.
Click to expand...
I mean, did you put GL4 or GL5 gear oil in it? GL4 is for manual transmissions and WON'T destroy the bronze/brass synchronizers while GL5 is for differential ONLY.
 
The GL-4 thing is NV4500 specific. 80W90 in a SM 465 is fine, but it does cause a fair bit of parasitic drag.
 
No bronze/brass "yellow metal" synchros in a SM465? Thought the top 3 gears were synchronized?
 
They are synchro'd, but not with some unobtainium like the NV4500 has. Regular brass synchro's in the SM465.
 
GL5 eats that stuff. Brass, bronze, whatever. It's unfriendly to the "yellow metals" in synchros.

GL4 is specifically mentioned mostly for manual trans. GL5 is meant for diffs. As manual transmissions in trucks have gotten less and less common GL4 has become harder to find. Learned all this lately while trying to figure out what fluid to put in my Tracker's transmission and transfer case. Owner's manual says Synchromesh fluid which I did a year ago and things have not been as smooth as hoped for. I know gear oil came out of it then. Meanwhile the transfer case won't shift into 4lo but moves between 2hi and 4hi. Chevy FSM and Suzuki call for 80w90 GL4...which everyone who runs seems to have no issues with. The rest of us with "parts store gear oil", Synchromesh, or whatever have issues.
From what a guy was saying over there it's sorta like the motor oil and cam break in thing going on now. The oil companies and parts stores never said much so a lot of people never noticed the difference and changes.
 
Spin the input shaft in neutral and hold the output shaft with your hand, does it slip? If so, then you are fine. Its cold and fresh and will have lots of drag until you actually drive it and heat it up. you should be okay as long as the gears shift properly and output shaft spins at the correct speed.

My NP435 and NP205 do the same thing even when in neutral, it goes away once the oil is warmed up and thinned out a little.
 
just a thought.......maybe you can chuck up a half inch drill to the input shaft,,,have someone operate the drill as you shift it through the gears......

In neutral you should be able to hold the output from turning with a prybar even with the drill spinning the input.
 
The input shaft only had a 1/2" of play when the bearing retainer cap was off. There is no play now that the cap is back on.

The fluid I used was 80w90 GL5. It's all they had at the store. I'll see if I can find GL4. There is a synchro on gears 1 2 and 3, but not granny and reverse.

I know the output shaft SHOULD spin freely in neutral, but it doesn't. My adapter plate is bolted on, so I stuck a large screwdriver in it and held it against the splines, and it is definitely spinning. I held the screwdriver against the output shaft splines in each gear, and felt how fast the output shaft was turning in each gear, and every gear felt appropriate for that gear. Neutral feels like 3rd gear.

I tried hooking my drill onto the input shaft. The shaft is too big.

Im really starting to think it had something to do with me turning the input shaft when the front bearing retainer was off. When I did this, the input shaft slid 1/2" out, and then I turned it some more. Getting it to slide back in took some wiggling and moving the shaft before it slid all the way on. While it was out, the synchro for 3rd gear was up against 3rd gear, and you could see the gap between the collar and the synchro.
Honestly would have never done this in the first place, but I took the cap off to replace the seal, hadn't put it back on, and some friends came over, we started messing with it, and I forgot I hadn't put the cap back on.
Maybe I should take the input shaft out and reassemble it to instructions and then see what happens... :confused:

Thanks!!
 
Like they said, there are bearings behind that input shaft, but I don't know if they could fall out or not with that amount of play.
And if they did, I'm not sure that you would not have heard it fall, or might be able to see one laying in there.
 
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