Sm 465 question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tommy217xxx · 09-10-2015, 03:12 PM

Hey everyone, I have a 76 gmc with a sm 465 trans and it shifts pretty rough. When I down shift into 2nd it usually grinds. It's kinda hard to find the gears when normally driving.

If I replace the shifter with it make the shifting smoother? Is it possible to replace the shifter and what does everyone like? The trans is a top load trans and the truck has a removable trans tunnel.

77 Big 10 · 09-10-2015, 03:55 PM

The SM465 is a top loaded, top shifting truck style transmission. The shifter, for lack of a better term is a "stick" that drops into the top of the trans. You can replace the stick if the bottom is worn and no longer is doing it's job. Hard to find gears can be worn internal shifting parts. The grinding can be clutch out of adjustment, or worn synchro teeth (dog ears). Try double clutching and slide it into gear.

Keith Seymore · 09-10-2015, 06:39 PM

Quote:

Originally Posted by 77 Big 10

The SM465 is a top loaded, top shifting truck style transmission. The shifter, for lack of a better term is a "stick" that drops into the top of the trans. You can replace the stick if the bottom is worn and no longer is doing it's job. Hard to find gears can be worn internal shifting parts. The grinding can be clutch out of adjustment, or worn synchro teeth (dog ears). Try double clutching and slide it into gear.

Agree.

Said differently the shifter is basically a giant screwdriver stuck in the top of the trans. Replacing it probably will not make any difference.

K

tucsonjwt · 09-10-2015, 08:04 PM

x2 on Keith's shifter info. I just had the clutch replaced and the input shaft re-sleeved on my SM465. I had hard shifting and it is better now. Unless this problem just came up, you know that grannys are not smooth shifters. The mechanics working on my truck said they rarely rebuild SM465s - usually the internals are in good shape. Aside from the worn input shaft, the one on my 83 was OK. With a bad clutch, you should hear some rattling and chattering when you shift.

tommy217xxx · 09-10-2015, 08:13 PM

On thing that I've noticed is the clutch pedal seems be walking up. The pedal starts to hum in 3rd and 4th gear. The first time I heard it I thought it was the dash vibrating. If I give it a tap it goes back down and stops vibrating.

franken · 09-11-2015, 12:49 AM

See the 3 holes in the shifter tower in the pic? I seem to recall the shifter is held in by a roll pin through there. There's an article somewhere about fixing a wallowed out hole in the shifter. It may help with finding but not grinding.
https://www.google.com/search?q=+sm4...ter&gws_rd=ssl

09-10-2015, 03:12 PM	#1
tommy217xxx Registered User Join Date: Oct 2014 Location: mi Posts: 359	Sm 465 question Hey everyone, I have a 76 gmc with a sm 465 trans and it shifts pretty rough. When I down shift into 2nd it usually grinds. It's kinda hard to find the gears when normally driving. If I replace the shifter with it make the shifting smoother? Is it possible to replace the shifter and what does everyone like? The trans is a top load trans and the truck has a removable trans tunnel. __________________ TJ 76 gmc 1500 swb patina finish Dropped 4/5, 350/4 speed 80 Chevy c10 lwb 305/350

09-10-2015, 03:55 PM	#2
77 Big 10 Registered User Join Date: Jul 2015 Location: La Quinta, CA. Posts: 131	Re: Sm 465 question The SM465 is a top loaded, top shifting truck style transmission. The shifter, for lack of a better term is a "stick" that drops into the top of the trans. You can replace the stick if the bottom is worn and no longer is doing it's job. Hard to find gears can be worn internal shifting parts. The grinding can be clutch out of adjustment, or worn synchro teeth (dog ears). Try double clutching and slide it into gear. Attached Images __________________ Paul

09-10-2015, 08:04 PM	#4
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,188	Re: Sm 465 question x2 on Keith's shifter info. I just had the clutch replaced and the input shaft re-sleeved on my SM465. I had hard shifting and it is better now. Unless this problem just came up, you know that grannys are not smooth shifters. The mechanics working on my truck said they rarely rebuild SM465s - usually the internals are in good shape. Aside from the worn input shaft, the one on my 83 was OK. With a bad clutch, you should hear some rattling and chattering when you shift.

09-10-2015, 08:13 PM	#5
tommy217xxx Registered User Join Date: Oct 2014 Location: mi Posts: 359	Re: Sm 465 question On thing that I've noticed is the clutch pedal seems be walking up. The pedal starts to hum in 3rd and 4th gear. The first time I heard it I thought it was the dash vibrating. If I give it a tap it goes back down and stops vibrating. __________________ TJ 76 gmc 1500 swb patina finish Dropped 4/5, 350/4 speed 80 Chevy c10 lwb 305/350

09-11-2015, 12:49 AM	#6
franken Registered User Join Date: Jun 2013 Location: Somewhere Posts: 3,100	Re: Sm 465 question See the 3 holes in the shifter tower in the pic? I seem to recall the shifter is held in by a roll pin through there. There's an article somewhere about fixing a wallowed out hole in the shifter. It may help with finding but not grinding. https://www.google.com/search?q=+sm4...ter&gws_rd=ssl



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