gmc to chevy tranny swap

[wc63]

i have a 63 gmc 305 v6 and the transmission is going out. my brother says its some kind of transmission or clutch ring that went out. when im driving i can hear loos plates sliding against each other. i was thinking of rebuilding it but some one close by is selling a 4 speed off a 65 chevy (c10 or c20) for a tempting price. is it easy to switch over to the four speed from the column. i know im going to have to cut a hole in the floor (which i wanted to avoid) but will the bolts and line up will the clutch linkage be in the same area? he's throwing in the clutch disk and press plate with the deal. any advice is appreciated.

[jgarverick]

sounds like you just need a new clutch man

[Hottrucks]

Originally Posted by jgarverick

sounds like you just need a new clutch man

Yep could be nothing more than a loose/broken spring on the disc.....does it rattle under a load?? or if you ride the peddle a bit ?? could be a throw out bearing???

but yes it will bolt to your bellhousing and theres NO WAY I would put a used disc or presure plate in ANYTHING there too cheap to even think about having to replace it later and Worse case is if there is a bearing bad in your trans the bearing kits are cheap too..any good trans shop will swap out the bearings quick and cheap ( I bought the kit from Napa)...I just went though this with a 56

[duallyjams]

If your truck is a 3 speed you have a low hump cab is the 4 speed out of a car or truck. The truck 4 speed with the granny low will require a high hump for the cab also sm420 and sm 465 the front retainer are different sizes so the bell housing would be different. A lot of little thing you just need to watch out for.

[wc63]

i didnt even think of the clutch. I've seen clutches go out and theres normally a certain smell that comes with it (in newer vehicles anyway) that i havent got from my truck. will napa carry these parts (clutch, press plate, throw out bearng) or do i have to go to the dealer. also, how do i figure out what tranny i have. the PO said the truck was all original, but i dont know what model it is. i think in 63 there was two options for the 3 speed GMC. i forgot to mention that i think i have a hydrualic clutch on the 63. my master cylinder has two lines feeding out. i also have a 66 GMC and that one has a smaller master cylinder with one line feeding out. I would assume the 63 is hydraulic and the 66 is manual. not sure if the 65 chevy would also be manual. if so, that would be another deterrent. and yes hottrucks, the tranny rattles while im shifting and messing with the clutch. sorry for all the questions but i dont want look dumb in front of someone else that might be able to see my face. thanks for the help guys.

[duallyjams]

60-63 have hydraulic slave cylinder 64-66 have mechanical . You can get a clutch from a parts store or have yours rebuilt.

[wc63]

I guess im going to replace the clutch. i found one at napa for $120. I figured if im going to take it down, i should proably have it rebiult. it occasionally pops out of second when its under load and the rpm's are low, also it wouldnt downshift into first unless the revs. were low. where can i find a rebuild kit. the guy at napa said they didnt have it (just rings and seals). ive looked online and cant find anything. also, i dont think imma do the rebuilding, i would have done the clutch but jumping in to the transmission is asking a littlle much. i just want to have everything for the when i take it to the shop. any info or advice is apprecieated.

[markeb01]

You really need to identify which transmission you have before buying parts for it. The clutch may be bad, but jumping out of gear is normally bad synchronizers in the transmission itself. Early 3 speed transmissions did not have synchros on 1st gear. Shifting into 1st gear was done at a dead stop or by double clutching. Later transmissions were synchronized on 1st and 2nd. If this is what you have and 1st gear isn’t working properly it’s likely that both 1st and 2nd synchros are shot. Your best source for finding parts will be a local manual transmission shop, or online.

Popping out of gear could also be caused by incorrectly adjusted shift linkage if you have a 3 speed on the column. If you have a granny 4 speed SM420, look for a local 4x4 specialist as these remain very popular transmissions with the rock crawling crowd. You can learn more about them here:

http://www.novak-adapt.com/knowledge/sm420.htm

[DetroitDan]

I'm interested in this question too, been looking at a 65 305/3 speed on the column, and was wondering what other options there are for transmission. Are there any autos that bolt up? I saw the thread about changing the floorpan to put a 4 speed in. Guess it would depend what condition this 3 speed is in. If it's all worn out like a lot of them are, might have to think about a 350/700r4 swap. But supposedly the 305 runs great..

[thebeast61]

Originally Posted by markeb01

You really need to identify which transmission you have before buying parts for it. The clutch may be bad, but jumping out of gear is normally bad synchronizers in the transmission itself. Early 3 speed transmissions did not have synchros on 1st gear. Shifting into 1st gear was done at a dead stop or by double clutching. Later transmissions were synchronized on 1st and 2nd. If this is what you have and 1st gear isn’t working properly it’s likely that both 1st and 2nd synchros are shot. Your best source for finding parts will be a local manual transmission shop, or online.

Popping out of gear could also be caused by incorrectly adjusted shift linkage if you have a 3 speed on the column. If you have a granny 4 speed SM420, look for a local 4x4 specialist as these remain very popular transmissions with the rock crawling crowd. You can learn more about them here:

http://www.novak-adapt.com/knowledge/sm420.htm

I just had mine rebuilt and had to get my parts from novak. My mechanic couldnt even locate the parts, i had to do it myself. I highly recommend novak, he was very helpful and the parts were high quality.

[wc63]

Originally Posted by thebeast61

I just had mine rebuilt and had to get my parts from novak. My mechanic couldnt even locate the parts, i had to do it myself. I highly recommend novak, he was very helpful and the parts were high quality.

thanks for the link. my mechanic said he would look for the parts but hansn't got back to me. I'll look them up.

[wc63]

woops. markeb01 posted the link...thanks again