sm465 Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

krsowles · 12-21-2009, 08:26 AM

Been a while since you all made my mind up to use a 4wd frame instead of converting a 2wd, thanks again. My latest issue is the 4wd tranny. lt seems to skip 3rd gear when shifting. When I drove it, l would shift into 3rd, but when l let the clutch out, it sure felt like 4th gear. The tranny is totally unknown as it came with the donor truck. It all looks, acts, shifts as it should. Seems fairly tight, no real slop or anything. I assumed when l opened the top it would all make sense to me but it all looks good in there too. l have heard about problems inherent with 3rd and 4th gear on this model so l'm hoping someone can point me in the right direction. One other note: many gears inside still have marking paint on them for the mesh pattern. Would this still be there from the factory or has someone opened recently - perhaps assembled wrong? Thanks in advance for the advice!

Shyguy · 12-21-2009, 11:06 AM

The only problem I have had with the compound four speed transmissions was when I had a '72 GMC back in '75 or so. If it was shifted fast between 2nd and 3rd it would hang up.

I have a compound 4 speed in both of my drivers and have never had a problem with either one of them.

Now when they are in 4th they feel like they are in 3rd speed and rpm wise.

I rarely ever use 1st since it is so low and never for normal driving. I do use it from time to time here around the farm when I want to go slow and pull something heavy though.

Hopefully some one else will chime in with more info.

Danny

krsowles · 12-21-2009, 04:41 PM

Thanks for the input shyguy. This tranny is unknown to us, but is the same as whats in the 72 2wd that is a daily driver. 1st gear, as you said, is rarely used. I go up through 2nd, 3rd, to 4th all real nice. With the donor tranny, l go from 2nd to 3rd, release the clutch and l swear l've hit 4th gear. l hope to get the 2wd tranny out tomorrow and open it up to compare, but l may have to swallow my pride and go to a tranny shop and have them look at it. l bet they've seen thousands of them. Thanks again, kelly

krsowles · 12-21-2009, 05:53 PM

Thread is dead, please feel free to remind me l'm being stupid whenever appropriate! ln shifting the gears on the bench, you can confirm the 4 gears are there and working fine. Musta had too much coffee or too little beer when l drove the donor truck around! Tranny is fine, thanks again!

**Wrenchbender Ret** · 12-21-2009, 05:54 PM

I've had some of those were the snap ring breaks that retains 3rd. gear on the counter shaft. It lets the gear slide forward & interferes with 4th. gear. Your symptoms are not quite the same but it is very likely that is what has happened. I used to take off the power takeoff cover & push the gear back were it belongs & weld it to the shaft. Before I would have a trans. guy rebuild it I would find another one. They are all over the place & normally in good shape as they are very rugged.

**bowtie72** · 12-21-2009, 05:56 PM

What happens when you put in in fourth? Does the rpm change more than third or like your down shifting. GM made a trans that 3rd and 4th are backwards. But i'm not sure if they were used in light duty trucks.

krsowles · 12-22-2009, 08:33 AM

Thanks for the ideas guys. The tranny is fine. l checked the snapring on third gear as l've heard of many issues. The rebuild kits now supply a spacer instead. Third is right where it needs to be. l literally had a brain fart and after opening the top, never shifted it through the gears manually. Each gear engaged beautifully as they should. l was so sure there was something wrong that l skipped a few steps and made a fool of myself!

Shyguy · 12-22-2009, 10:39 AM

Don't feel bad, we have all done some stuff or thought of something that was not quite right.

Speaking of those 4 speeds, some people do not realize how darn heavy they are and try to man handle them by themselves.

Here is what happened to us when we put one in my '67. We had a heck of a time getting it in because of the weight size, but finally succeed with a lot of sweat and a few choice words.

After we got it in we turned around and saw the cherry picker and realized we put the transmission in the hard way. It would have been easy using the cherry picker instead of man power.

Heck this is just one example of many fun things my son and I have done working on these old trucks.

Danny

12-21-2009, 08:26 AM	#1
krsowles Registered User Join Date: Oct 2009 Location: Colchester, VT Posts: 7	sm465 Question Been a while since you all made my mind up to use a 4wd frame instead of converting a 2wd, thanks again. My latest issue is the 4wd tranny. lt seems to skip 3rd gear when shifting. When I drove it, l would shift into 3rd, but when l let the clutch out, it sure felt like 4th gear. The tranny is totally unknown as it came with the donor truck. It all looks, acts, shifts as it should. Seems fairly tight, no real slop or anything. I assumed when l opened the top it would all make sense to me but it all looks good in there too. l have heard about problems inherent with 3rd and 4th gear on this model so l'm hoping someone can point me in the right direction. One other note: many gears inside still have marking paint on them for the mesh pattern. Would this still be there from the factory or has someone opened recently - perhaps assembled wrong? Thanks in advance for the advice!

12-21-2009, 11:06 AM	#2
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: sm465 Question The only problem I have had with the compound four speed transmissions was when I had a '72 GMC back in '75 or so. If it was shifted fast between 2nd and 3rd it would hang up. I have a compound 4 speed in both of my drivers and have never had a problem with either one of them. Now when they are in 4th they feel like they are in 3rd speed and rpm wise. I rarely ever use 1st since it is so low and never for normal driving. I do use it from time to time here around the farm when I want to go slow and pull something heavy though. Hopefully some one else will chime in with more info. Danny __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.

12-21-2009, 04:41 PM	#3
krsowles Registered User Join Date: Oct 2009 Location: Colchester, VT Posts: 7	Re: sm465 Question Thanks for the input shyguy. This tranny is unknown to us, but is the same as whats in the 72 2wd that is a daily driver. 1st gear, as you said, is rarely used. I go up through 2nd, 3rd, to 4th all real nice. With the donor tranny, l go from 2nd to 3rd, release the clutch and l swear l've hit 4th gear. l hope to get the 2wd tranny out tomorrow and open it up to compare, but l may have to swallow my pride and go to a tranny shop and have them look at it. l bet they've seen thousands of them. Thanks again, kelly

12-21-2009, 05:53 PM	#4
krsowles Registered User Join Date: Oct 2009 Location: Colchester, VT Posts: 7	Re: sm465 Question Thread is dead, please feel free to remind me l'm being stupid whenever appropriate! ln shifting the gears on the bench, you can confirm the 4 gears are there and working fine. Musta had too much coffee or too little beer when l drove the donor truck around! Tranny is fine, thanks again!

12-21-2009, 05:54 PM	#5
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,194	Re: sm465 Question I've had some of those were the snap ring breaks that retains 3rd. gear on the counter shaft. It lets the gear slide forward & interferes with 4th. gear. Your symptoms are not quite the same but it is very likely that is what has happened. I used to take off the power takeoff cover & push the gear back were it belongs & weld it to the shaft. Before I would have a trans. guy rebuild it I would find another one. They are all over the place & normally in good shape as they are very rugged.

12-21-2009, 05:56 PM	#6
bowtie72 Registered User Join Date: Mar 2007 Location: Colorado Posts: 359	Re: sm465 Question What happens when you put in in fourth? Does the rpm change more than third or like your down shifting. GM made a trans that 3rd and 4th are backwards. But i'm not sure if they were used in light duty trucks. __________________ 1968 SWB "Little White Truck" 1972 LWB LS 4l80 "Plain Jane!!"

12-22-2009, 08:33 AM	#7
krsowles Registered User Join Date: Oct 2009 Location: Colchester, VT Posts: 7	Re: sm465 Question Thanks for the ideas guys. The tranny is fine. l checked the snapring on third gear as l've heard of many issues. The rebuild kits now supply a spacer instead. Third is right where it needs to be. l literally had a brain fart and after opening the top, never shifted it through the gears manually. Each gear engaged beautifully as they should. l was so sure there was something wrong that l skipped a few steps and made a fool of myself!

12-22-2009, 10:39 AM	#8
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: sm465 Question Don't feel bad, we have all done some stuff or thought of something that was not quite right. Speaking of those 4 speeds, some people do not realize how darn heavy they are and try to man handle them by themselves. Here is what happened to us when we put one in my '67. We had a heck of a time getting it in because of the weight size, but finally succeed with a lot of sweat and a few choice words. After we got it in we turned around and saw the cherry picker and realized we put the transmission in the hard way. It would have been easy using the cherry picker instead of man power. Heck this is just one example of many fun things my son and I have done working on these old trucks. Danny __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.



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