SM420 Transmission Shifter Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

67_C-30 · 03-21-2005, 10:41 AM

I have a SM420 4 speed in my '67 C-30. The transmission works very good. It shifts very smooth, and is very quiet. It only has 61,000 miles. The only thing about it is that the shifter kinda rattles in 4th gear. Are there bushings that can be replaced to stop this, or is there something else you have to do. I've never torn into one, so I know nothing about them. TIA!

67_C-30 · 03-21-2005, 09:03 PM

ttt

Robert1970C20rstbukt · 03-21-2005, 09:14 PM

Usually after about 30 years the tip of the shifter that goes into the top of the tranny can break loose and wobble around, which causes slop in the shifter. The shifter in the 465 I'm putting in my truck is the same way, but it wobbles in all gears due to the tip of the shifter being loose. Hope this helps.

CE20934 · 03-21-2005, 10:29 PM

IIRC, the shifter is two pieces. One is the long rod the knob attaches to, the other is a small shaft (the tip Robert is talking about) that slips inside the long rod & is machined to slide around the shifter rails.

When I cleaned up my SM420, I pulled that small shaft out, put some new O-rings on it, slid it back in, and replaced the roll pin that holds it inside the long rod.

However, that's not going to get rid of ALL the slop. The machined flats in the shifter rails are quite a bit larger than the ball end of the small shaft. AFAIK, there's no bushing that slides over that ball end.

67_C-30 · 03-22-2005, 12:19 AM

Did the O rings help it though? If the tip is broken, can they be bought new, or will I have to try to find a good used one? Thanks again!

stickshift_or_walk · 03-23-2005, 05:14 PM

My local GM parts guy (who I trust about as far as I can throw my truck) says the tip isn't available separately - you have to buy the entire shift lever. Oh, wait - never mind. That part has been discontinued.

I was asking for the SM465 lever, which I know was used through 1987. That doesn't bode well for the SM420.

I hope someone here knows better, that there is still a source for such a common part. Is someone aware of a GM dealership somewhere that is friendly to us pre-73 fanatics and will ship nationwide?

SSOW

CE20934 · 03-23-2005, 10:05 PM

Quote:

Originally Posted by 67_C-30

Did the O rings help it though? If the tip is broken, can they be bought new, or will I have to try to find a good used one? Thanks again!

The O-rings helped, yes. Not a whole lot, but a bit.

Your tip isn't broken. Trust me, if that little tip is broken, you're not going to be rowing any gears at all. Plus it's damn near impossible to break them, especially from normal use.

67_C-30 · 03-24-2005, 11:13 PM

I guess when I do the engine swap, I'll try the O rings and inspect all the parts for anything unusual. Thanks for help!

03-21-2005, 10:41 AM	#1
67_C-30 I have a radical idea! Join Date: Jan 2005 Location: Sweet Home Alabama! Posts: 6,513	SM420 Transmission Shifter Question I have a SM420 4 speed in my '67 C-30. The transmission works very good. It shifts very smooth, and is very quiet. It only has 61,000 miles. The only thing about it is that the shifter kinda rattles in 4th gear. Are there bushings that can be replaced to stop this, or is there something else you have to do. I've never torn into one, so I know nothing about them. TIA! __________________ '67 C-30 Dually Pickup 6.2 Turbo Diesel, NP435 ‘72 C-10 SWB , 350 4bbl, TH350 '69 C-10 SWB , 250 L6, 3 OTT '69 GMC C3500, dump truck, 351 V6, NP435 '84 M1009 CUCV Military Blazer 67 C-30 Turbodiesel build thread http://67-72chevytrucks.com/vboard/s...d.php?t=254096 My trucks http://s226.photobucket.com/albums/d...ediafilter=all Member of the 1-Ton Club!

03-21-2005, 09:03 PM	#2
67_C-30 I have a radical idea! Join Date: Jan 2005 Location: Sweet Home Alabama! Posts: 6,513	ttt __________________ '67 C-30 Dually Pickup 6.2 Turbo Diesel, NP435 ‘72 C-10 SWB , 350 4bbl, TH350 '69 C-10 SWB , 250 L6, 3 OTT '69 GMC C3500, dump truck, 351 V6, NP435 '84 M1009 CUCV Military Blazer 67 C-30 Turbodiesel build thread http://67-72chevytrucks.com/vboard/s...d.php?t=254096 My trucks http://s226.photobucket.com/albums/d...ediafilter=all Member of the 1-Ton Club!

03-21-2005, 09:14 PM	#3
Robert1970C20rstbukt Registered User Join Date: Jun 2004 Location: Beeville, Texas Posts: 1,943	Usually after about 30 years the tip of the shifter that goes into the top of the tranny can break loose and wobble around, which causes slop in the shifter. The shifter in the 465 I'm putting in my truck is the same way, but it wobbles in all gears due to the tip of the shifter being loose. Hope this helps. __________________ RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck

03-21-2005, 10:29 PM	#4
CE20934 Senior Member Join Date: Apr 2002 Location: Help! I'm in an office park with its own network of freeways! Posts: 470	IIRC, the shifter is two pieces. One is the long rod the knob attaches to, the other is a small shaft (the tip Robert is talking about) that slips inside the long rod & is machined to slide around the shifter rails. When I cleaned up my SM420, I pulled that small shaft out, put some new O-rings on it, slid it back in, and replaced the roll pin that holds it inside the long rod. However, that's not going to get rid of ALL the slop. The machined flats in the shifter rails are quite a bit larger than the ball end of the small shaft. AFAIK, there's no bushing that slides over that ball end. __________________ '67 C20--427 tall deck/SM420, 4.10 HO52 (Michigan has not been kind to the Old Man) '95 Caprice--355 LT1/T56/3.42 8.5" 10-bolt (daily driver, almost 300k on the chassis) '07 Outback--wife's car. 125k & counting. No head gasket or transmission issues yet. fingers crossed

03-22-2005, 12:19 AM	#5
67_C-30 I have a radical idea! Join Date: Jan 2005 Location: Sweet Home Alabama! Posts: 6,513	Did the O rings help it though? If the tip is broken, can they be bought new, or will I have to try to find a good used one? Thanks again! __________________ '67 C-30 Dually Pickup 6.2 Turbo Diesel, NP435 ‘72 C-10 SWB , 350 4bbl, TH350 '69 C-10 SWB , 250 L6, 3 OTT '69 GMC C3500, dump truck, 351 V6, NP435 '84 M1009 CUCV Military Blazer 67 C-30 Turbodiesel build thread http://67-72chevytrucks.com/vboard/s...d.php?t=254096 My trucks http://s226.photobucket.com/albums/d...ediafilter=all Member of the 1-Ton Club!

03-23-2005, 05:14 PM	#6
stickshift_or_walk Left Foot Functioning Join Date: May 2004 Location: Duncan, OK Posts: 348	My local GM parts guy (who I trust about as far as I can throw my truck) says the tip isn't available separately - you have to buy the entire shift lever. Oh, wait - never mind. That part has been discontinued. I was asking for the SM465 lever, which I know was used through 1987. That doesn't bode well for the SM420. I hope someone here knows better, that there is still a source for such a common part. Is someone aware of a GM dealership somewhere that is friendly to us pre-73 fanatics and will ship nationwide? SSOW __________________ 69 C10 (#1 son's ride) 72 C20 (Dad's farm truck) 82 K30 (Ex - brush pumper project)

03-24-2005, 11:13 PM	#8
67_C-30 I have a radical idea! Join Date: Jan 2005 Location: Sweet Home Alabama! Posts: 6,513	I guess when I do the engine swap, I'll try the O rings and inspect all the parts for anything unusual. Thanks for help! __________________ '67 C-30 Dually Pickup 6.2 Turbo Diesel, NP435 ‘72 C-10 SWB , 350 4bbl, TH350 '69 C-10 SWB , 250 L6, 3 OTT '69 GMC C3500, dump truck, 351 V6, NP435 '84 M1009 CUCV Military Blazer 67 C-30 Turbodiesel build thread http://67-72chevytrucks.com/vboard/s...d.php?t=254096 My trucks http://s226.photobucket.com/albums/d...ediafilter=all Member of the 1-Ton Club!

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