Sm465 issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tommy217xxx · 12-13-2015, 08:26 PM

Hey everyone, my truck has an sm465 4 speed in it. Sometimes when I try to put the truck in reverse it seems like something is stuck. Meaning I can't get it to go into neutral or any other gear. When I release the clutch the truck stalls. When I try to let out the clutch and give it gas the truck doesn't move at all. I've noticed when I'm coming in to back her in, if I go right into neutral then into reverse theres no problem but if I go from first or second into reverse that's when it feels like somethings stuck. It almost feels like it's not releasing the gear and going into neutral. When the issue happens I try to move the gear shift to the neutral position and give it a side to side shake and nothin. Eventually the truck will go into gear but it can take a while.

Sorry for the long explanation because I'm not really sure how to describe the problem.

tucsonjwt · 12-14-2015, 10:55 AM

I don't know, but on my SM465 a bad clutch accounted for most of my shifting problems. Do you know that you have a good clutch?

tommy217xxx · 12-14-2015, 02:32 PM

I bought the truck about 4 months ago and the guy I got it from said he put a new clutch in it. I'm gonna put it on the lift and look at it. This trans has given me problems since I got the truck. I might look for something else.

tucsonjwt · 12-14-2015, 04:59 PM

Unless you don't like the truck, I would do some investigation on the clutch and transmission.

SM465s are not smooth shifting transmissions (relative to later model manual transmissions) but the they are very durable. Most transmission guys I have talked to said they rarely need to rebuild a SM465. My PTO coves leak a little fluid, so I will need to replace the gaskets at some point. Have you checked the fluid level in your transmission?

First gear is usually a bit difficult to engage (I was told it is sqaure cut, not syncromesh) and reverse sometimes requires letting the clutch out in neutral prior to engaging (double clutching) on my truck. Also, there is no overdrive gear, so fuel economy will not match a 5 speed (I do have a gear vendor installed by the PO of my truck, so that accomplishes and overdrive for me.)

12-13-2015, 08:26 PM	#1
tommy217xxx Registered User Join Date: Oct 2014 Location: mi Posts: 359	Sm465 issue Hey everyone, my truck has an sm465 4 speed in it. Sometimes when I try to put the truck in reverse it seems like something is stuck. Meaning I can't get it to go into neutral or any other gear. When I release the clutch the truck stalls. When I try to let out the clutch and give it gas the truck doesn't move at all. I've noticed when I'm coming in to back her in, if I go right into neutral then into reverse theres no problem but if I go from first or second into reverse that's when it feels like somethings stuck. It almost feels like it's not releasing the gear and going into neutral. When the issue happens I try to move the gear shift to the neutral position and give it a side to side shake and nothin. Eventually the truck will go into gear but it can take a while. Sorry for the long explanation because I'm not really sure how to describe the problem. __________________ TJ 76 gmc 1500 swb patina finish Dropped 4/5, 350/4 speed 80 Chevy c10 lwb 305/350

12-14-2015, 10:55 AM	#2
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,188	Re: Sm465 issue I don't know, but on my SM465 a bad clutch accounted for most of my shifting problems. Do you know that you have a good clutch?

12-14-2015, 02:32 PM	#3
tommy217xxx Registered User Join Date: Oct 2014 Location: mi Posts: 359	Re: Sm465 issue I bought the truck about 4 months ago and the guy I got it from said he put a new clutch in it. I'm gonna put it on the lift and look at it. This trans has given me problems since I got the truck. I might look for something else. __________________ TJ 76 gmc 1500 swb patina finish Dropped 4/5, 350/4 speed 80 Chevy c10 lwb 305/350

12-14-2015, 04:59 PM	#4
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,188	Re: Sm465 issue Unless you don't like the truck, I would do some investigation on the clutch and transmission. SM465s are not smooth shifting transmissions (relative to later model manual transmissions) but the they are very durable. Most transmission guys I have talked to said they rarely need to rebuild a SM465. My PTO coves leak a little fluid, so I will need to replace the gaskets at some point. Have you checked the fluid level in your transmission? First gear is usually a bit difficult to engage (I was told it is sqaure cut, not syncromesh) and reverse sometimes requires letting the clutch out in neutral prior to engaging (double clutching) on my truck. Also, there is no overdrive gear, so fuel economy will not match a 5 speed (I do have a gear vendor installed by the PO of my truck, so that accomplishes and overdrive for me.)



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