I’ve got a ‘73 Blazer that I’ve always wanted to convert from an automatic to 4-speed. I think I’ve found a donor truck which is completely stock, a 1986 Chev Silverado 2500. They both have 350 engines(not positive about the donor truck). Will the tranny, transfer case, etc., go from the 2500 to my Blazer without too many issues? Anything else to be sure to check out? Thanks
CK5
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Compatibility question
- Thread starter RJG
- Start date
Pretty much everything should swap over - get EVERYTHING from the donor. Grab the crossmember, driveshafts, pedal assembly, tcase shifter assembly with trim, everything.
The drivetrain stuff should all easily go in your truck, the only things you might have problems with are the flywheel, axle end u-joints and if the pedals will fit your earlier cab.
The hydraulic clutch set up (pedals, m/c, slave, bellhousing) is very desirable so that is a great score.
You'll need a flywheel for your motor and I'm not sure if the flywheel from the '86 motor will fit your existing motor (1 pc vs 2 pc rear main seal cranks are different).
Your '73 likely has a 203 tcase and the '86 will have a 208 so the shifter location will be a little different.
The drivetrain stuff should all easily go in your truck, the only things you might have problems with are the flywheel, axle end u-joints and if the pedals will fit your earlier cab.
The hydraulic clutch set up (pedals, m/c, slave, bellhousing) is very desirable so that is a great score.
You'll need a flywheel for your motor and I'm not sure if the flywheel from the '86 motor will fit your existing motor (1 pc vs 2 pc rear main seal cranks are different).
Your '73 likely has a 203 tcase and the '86 will have a 208 so the shifter location will be a little different.
You can retrofit factory hydro clutch system to an earlier square. You need to create a template of the mounting holes and pushrod hole for the clutch master cylinder off of the truck the parts are coming from. There is room for it on the early firewall but you need the locations for the holes accurately transferred to it.
The support rods under the dash that are part of the clutch pedal box have studs that go through the firewall for the clutch master cylinder. Once the holes are in the right spot it’s just a matter of swapping all the parts over.
The support rods under the dash that are part of the clutch pedal box have studs that go through the firewall for the clutch master cylinder. Once the holes are in the right spot it’s just a matter of swapping all the parts over.
Nobody likes mechanical clutch linkage anymore. I remember my first square body with a NP465. There was no such thing as a hydraulic clutch yet on GM trucks. I think there was for smaller Japan's vehicles, but not full size GM trucks.
My only issue with mechanical linkage is that when you get the truck twisted up offroad you lose your clutch, works fine on the street though. If I was swapping a vehicle that will only see street time or moderate dirt roads Id see no issue with mechanical.
If you have a 203 tcase now the 208 shifter will drop down in the hole in the floor but will be too far to the right, IIRC I had to cut about 1" over for it to be in the right spot, did the 86s still have the removable trans tunnel? If so Id grab that too.
If you have a 203 tcase now the 208 shifter will drop down in the hole in the floor but will be too far to the right, IIRC I had to cut about 1" over for it to be in the right spot, did the 86s still have the removable trans tunnel? If so Id grab that too.
Thanks, an update, I bought the 2500, seller says it’s a great runner, I’ll be able to drive it home (about 150 miles) with no problem. So, I’ll have all the parts. $2500. Granted, the body is rough but I don’t care…
I've had both. My '75 was a factory 4-speed with mechanical clutch linkage. It felt heavier than the later hydraulic setup we swapped into my '91. I didn't have a heavy effort pressure plate on the '75 either. Just an off-the-shelf Luk clutch for the truck. I did run into an issue with it twisted up off-road that was odd, but that's probably a stack up of worn pivots on the z-bar and junk body bushings causing more deflection than average.
The stock squarebody hydraulic system still uses a conventional fork and throwout bearing over the later integrated slave/release bearing setup used on my nv4500. The bonus to that is you can physically bleed the clutch system OFF the truck. It's as simple as clamping a board in your vise and bolting the clutch master cylinder and slave to the board. Hook up the line between the two and bleed it. Bolt the whole system back in the truck as a unit.
1986 was the year that GM went to a one piece rear main seal so if it still has an 86+ motor, as John said, another two piece rear main flywheel will be needed.
Thanks, I will only be using on the street, should be OK.
Thanks for your reply. Just so I fully understand, my Blazer currently has a 1976 350 from a Camaro. Current transmission is stock TH350 and stock 203 tcase. Assuming I could go with either engine, would I be better off to just transplant the entire driveline from the truck to the Blazer? Could I encounter issues with engine and transmission mounts? Sorry, I'm new at this...
Does the engine you currently have need any work? Does the engine from the 86 run better/worse than what you have? You can swap the entire engine if you wish, the crossmember you want will be the one off the 86 with the SM465 and it may need to be moved forward on the frame, I can’t remember if the 350 holes are the same, I know 400 needs moved….the engine is a direct bolt in affair from the 86 to yours. You will probably need a new rear driveshaft as the truck one is too long and your blazer one will be too short plus the 86 is a slip yoke transfer and yours is a bolted yoke.
One of the things that makes GM stuff easy is that for many years a lot of drivetrain parts would interchange with relative ease.
As said earlier all the components will change over if you keep the correct parts to aid in the swap - things like crossmember for the trans/t-case ( your 86 should be a short adapter that requires and 85+ "W" type crossmember while your old one will be more flat across the center for a taller adapter that the TH350/203 used ).
Keep your donor truck until the swap is complete - this way you have absolutely everything that you will need. Best of luck to Ya' !
Damn I type slow.....
I believe that the 86 465/208 combo is farther back for X-member bolts holes - seems like they went somewhat universal when the changed up the adapters in 85.
interesting - i never looked close enough to see if it would be a pain to pull the lines out and put them back
Lines? It’s just one from the master to the slave. Might be 16-18” long. I’ve witnessed my buddy Larry doing that exact procedure on his K10 and his Burb.
He was having issues with the clutch on the burb and could never get it to feel consistent at all. So he replaced both separately re-bled and tried again. He had grown tired of having to ask his wife to come out to the garage to press the pedal down. It was probably the other way around that she grew tired of pressing the pedal down over and over.
It will come off and go back on as a unit for sure.
Having had a lot of both hydraulic and mechanical clutch setups, the hydraulic setup is much better. Especially offroad. Sucks losing your clutch pedal off road.
Martin
Martin
