I have 2 4x4's both using the sm465 trans both act exactly the same. My trucks will not downshift into 1st (not low) if the truck is rolling at all. Is that normal? The truck will downshift from 3rd to 2nd no problem but will not go into 1st untill it comes to a complete stop then it drops right in. If you put alot of pressure on the lever it will just grind. No i'm not trying to downshift into low I know that gear is not syncronised for that. If you start in low it will upshift thru all the gears perfectly. 1st gear dont have a "overspeed" locking syncro does it?, that keeps from overrevving the motor with downshifting.
CK5
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SM 465 trans shifting question
- Thread starter GMC Truck
- Start date
My 465 doesn't like to downshift into 2nd (assuming 1st is low/granny) unless I'm going real slow or stopped. If I put slight presure on the lever towards 2nd while coasting (usually around a corner) it will fall right in (clutch pedal up) when the truck slows down enough. Sounds like yours is normal. Rember these were designed in the 1960's as truck transmissions. Not to be shifted quickly.
cdoggwsu
1/2 ton status
That's normal for me as well, but I've gotten in the habit of double clutching on my downshifts and then it's not a problem. As long as you're not going a speed that's beyond the rpm range of 1st gear (2nd as some are calling it) it'll drop in.
As to why you can shift through 1st while moving if you started in L, my guess is it's a function of wheel speed since you can hardly get moving in L but if you're trying to downshift into 1st you're most likely going over 10mph.
As to why you can shift through 1st while moving if you started in L, my guess is it's a function of wheel speed since you can hardly get moving in L but if you're trying to downshift into 1st you're most likely going over 10mph.
cdoggwsu
1/2 ton status
Yeah it definitely wasn't what I expected when I first bought my Blazer.
All I had driven before that were pickups with NV3500/4500's and dump trucks. I knew the manual Blazers were 4-speeds but I had no idea it'd drive more like an Eaton-Fuller and less like a pickup.
Now that I'm used to driving it an NV3500 feels like it's going to fall apart under my feet and a 4500 is so smooth it just feels like cheating.
All I had driven before that were pickups with NV3500/4500's and dump trucks. I knew the manual Blazers were 4-speeds but I had no idea it'd drive more like an Eaton-Fuller and less like a pickup.
Now that I'm used to driving it an NV3500 feels like it's going to fall apart under my feet and a 4500 is so smooth it just feels like cheating.
All SM465's had straight cut teeth, and NO synchro's in the granny low!..it's meant to be engauged only at a standstill,but if your real skilled at double clutching,you might be able to get it into granny low ,but you'd better be going 5 mph or less!..there aint much you cant pull or climb in "second" gear from a standstill anyway in a full sized GM truck..grany low is for climbing walls or taking off on a steep hill with a loaded trailer in tow,etc..
For the sake of discussion, 1st will be "Low" going 2, 3, 4. When starting from a standstill in 1st gear, the shift into 2nd is easy because the gears on the engine side of the clutch are slowing down to meet the next gear, which is why it is easy to shift going up. But downshifting from 3rd to 2nd, you have to speed the gears up in order to make the shift. On these older transmissions, parts get worn out, and the syncro has a hard time doing that task. If I am doing less than 10 mph, I can pull the shifter hard enough (with a bit of double-clutching) and engage 2nd gear.
broncoman6524
1/2 ton status
Rev-match it.
Mine does the same thing, if you really need to get it into(or 2nd, NON low)
1st try it. Works everytime for me
Mine does the same thing, if you really need to get it into(or 2nd, NON low)
1st try it. Works everytime for me
Just like a semi-truckRev-match it.
Mine does the same thing, if you really need to get it into(or 2nd, NON low)
1st try it. Works everytime for me
Yeah I can shift mine down from 3rd at a pretty good speed. You just need to throw a rev to get things moving... works for low too... but not as easy.
