trany conversion

[orchie]

i have a 84 gmc sierra and i was wondering if anybody has any tips on converting my automatic tranny to a four speed with a hydraulic clutch . i have all the hard ware but not the trouble shooting tips tks andy:canada

[79D604SPD]

I did basically the same conversion on my 79 K20. Went from a th400 to a SM465 4 speed(liked the old 3spd th400, but will never go back). The difference with mine is it is still the old style linkage setup(non-hydraulic) and I ran into problems with that because of my body-lift. My clutch z-bar had to be lengthened to compensate for the added distance now between the body and frame. As far as the hydraulic clutch, the only thing I could think of is lengthening the hoses if you had a lift. Some hardware stores or farm implement dealers could make hoses if you needed them. I'm not sure where the clutch master cylinder mounts or where the slave cyl. mounts but maybe a service manual could help. And I'm not sure if the bellhousing is different with a hydraulic clutch but a junkyard or parts store could help with that by checking for different part numbers between the years. When you put the trans in, make sure the release-bearing arm is in good shape as this could cause release problems if its not. Also check the release bearing snout on the transmission for wear, or warpage, as this could cause premature release bearing problems. I moved the trans crossmember forward into already drilled factory holes on mine, but I think they changed crossmembers in the 80s. It depends on the transfer case too I think. Mine is the NP205. A nice transmission jack helps if you are doing the conversion on the ground. And after aligning the clutch, the transmission should slide somewhat easily together with the bellhousing, with some persuasion. Don't pull the transmission and bellhousing together with the trans bolts as this can break off the ears on the transmission. Driveshafts are different lengths too, even between 1/2, 3/4, and 1 tons. I bought a junk donor truck that had all the parts so I didn't have to do too much searching. Hopefully some of this might help.