Hello, long time viewer, very few posts! I have a 58 GMC 100 Fleetside pickup with a 336 Pontiac 4 speed hydramatic. It runs and drives but there are multiple issues with both the engine and the tranny. I checked the numbers and fortunately / unfortunately it is not a numbers matching driveline. I am looking to replace at least the engine and tranny, possibly the rear end. I've been on Craigslist and found a 1984 Corvette with a 350 / 700r4 tranny and was wondering if this would be a good donor car for the driveline etc..? The car is $2200 and has 67k miles on it but the tranny slips. Also, would any of the suspension stuff work with the GMC? If not what would be a better donor car? Thanks all, I've really enjoyed the site! Carl
Motor and trans is good choice some may like the tpi some not you can switch to carb if it's not up to par. I believe you can run 15" wheels with the suspension to keep the look traditional. Please don't run big late model wheels Sent from my iPhone using The H.A.M.B. mobile app
the suspension is probably a bit too wide, and would also be a fun challenge to install. I don't really see why you'd want to....maybe something a bit more mild would work? That's a lot of money for a crappy engine and burned up trans. The 84 model was crossfire injection, which is not very high on many peoples "dream engine" list. I'd sooner buy a new GM crate 350, and find another trans to rebuild. See what ratio rear the truck has in it...it's likely a Spicer 40 or something like that, it may possibly have a tag on one of the rear cover bolts with the ratio or the number of gear teeth on the gears, stamped on it.
A 350 Chevy and trans fit in there like it was made for it, because...well, it essentially was. The Chevy version came with a small block Chevy (283) as an option although you wouldn't be able to mount it the same way because the GMC front cross member is different from the Chevy. Doesn't make any difference though if you use side motor mounts (which is what you should do, in my opinion). I have a 350 in my '58 GMC with the original GMC Spicer rear diff. Everything fits great with room to spare. Not sure about all the Corvette suspension stuff. My guess is the track width is wider than your pickup.
Squirrel (see post #3) is an authority on this era of GM trucks so listen to what he says. he has a point about that particular motor and trans. If the trans is no good and needs to be rebuilt then all your getting for your project out of that Vette is a questionable motor of a not-very-desirable vintage. For $2,200 (or a little less) you could get a new crate motor.
OK, thanks for the responses guys, this is exactly the advice I was looking for. So I'll pass on the Vette lol, and check into a 350/700r4 with trans-dapt motor mounts. I was looking for a car or truck so I would have all the peripheral stuff, alternator power steering pump etc.. Carl
Was the 336 Pontiac a front or side mount engine in the 58 truck? If it was a front mount engine, then the frame will have bell housing aligned side mounts. You may need to build both new front and rear crossmembers for mounting newer engine/trans. Perhaps you may want to use a W engine such as a 348 and a cast iron Powerglide.
The 336 is front mounted so I was hoping trans-dapt would have some motor/tranny mounts available. My main concern is if the from cross member is structural or not. If it is I may need to find one from a Chevy and do some ciphering. ;>) Hey Blackjack, I think shipping to the UK may be cost prohibitive! Good luck on your search.
you do not need trans-dapt mounts.use 1966 impala 327 motor amd trans mount.you can get trans and engine crossmember from speedway if you can not make them yourself have to weld engine to frame.I usually make my own .Your truck is an easier swap.Get crate 350,turbo 350 or 700r4 trans .Stay away from the vette.Jimmie King
I'm thinking this is a golden opportunity to use a later Pontiac engine and trans. Or maybe rebuild the Hydramatic and replace the engine with a 389 or 421.
Mopar, there are no vettes for me in the near future! Rusty, the Pontiac engine would have to be a pre-1961 because later engines are mounted side to side. Not to say it's not an option but.... The more I learn, the more I'm leaning toward a 350 / 700r4. I'll be gathering parts through the winter and starting the work in spring. I don't have a heated garage and I'm old lol. Carl-
I'm sure you've heard the saying "the vette makes them wet", but I suspect in this case "the vette you'll regret". Sounds to me you made the decision not to buy it....good choice. As that 2200 can be spent more wisely elsewhere.
I'd have to go with a '59 or '60 Pontiac 389.. It's a direct bolt-in to the truck and it bolts up against the 4 speed hydro. Parts are available. AND! I'd search out a 55-56 front clip for it.
IIRC: 1958 and up Pontiac 370, 389, 421, etc. are side mounted. 58-60 are the only blocks that will bolt to the existing hydro. 1961 and up use BOP pattern.
The 84 Corvette had unbelievably awful reliability issues. Many engine faults, fuel system issues, the worst TH 700 R4 of the entire generation, and was prone to evil handling from poor reared bushings and components. The p. Steering rack was prone to leaks and sticking as well. Ask me how I know. Run away as fast as your feet will carry you from that dog. Sent from my iPad using The H.A.M.B. mobile app
Yea, I've been severely counseled on the vette option lol. Not going down that road. So a few of you recommend going with a Pontiac block and keeping the 4 speed hydromatic. If I do that I would have to rebuild the tranny cuz it leaks like crazy and shifts REALLY hard from 2nd into 3rd. Is it strong enough to handle the larger engines? Maybe a 389 is the way to go, the 336 parts are expensive, maybe not so much for the 389? Suspension and brakes are on the list too. Carl-
Last time I looked, the Buick, Olds and Cads were still reasonably priced and not usually beat to death. http://denver.craigslist.org/pts/5883890546.html .
do not throw away the current 336 w/ 4spd hydramatic - this combination is very hard to find - put in a good dry place and place some ads
dont want to step on this post BUT IVE STILL GOT MY 58 GMC 337 MOTOR AND 4 SPEED TRUCK THAT IM PARTING OUT motor runs good -does have a bad water pump ,this is a complete drive line truck with exh manifolds clutch trans starter driveshaft and rear axle -3/4 ton thanks mike
Use the hydro! Easily sealed up when the engine is removed. Pull the torus and it's members off the transmission and replace the front seal. Re-install the torus and members. While out, change the rear seal too. Easier outside of the vehicle. When re-installing the hydro use PLIOBOND 30 to seal the flywheel to the new engine's crankshaft flange. Also use this on the flywheel bolt threads. Coat the 30 bolt gasket with gasket sealer. The 18 bolt o-ring just gets some vaseline to hold into place in flywheel groove. (You have either the gasket or the oring.) Remember to install a pilot bearing if the 389 does not have one before mating the engine to transmission. Finally change both side and bottom pan cover gaskets. The side cover will also get linkage seals. This should seal the transmission up really well.
The 4 speed Hydros are VERY TOUGH transmissions. Just check out what many of the early 60's gas class drag cars used for transmissions.......4 speed Hydros. By the way, they naturally shift hard. Even when they were new.
Excellent replies folks, and I am excited to fix / keep the hydro. So now I have a plan. I am going to find a 389 4bbl and rebuild it, redo the suspension with posies super slider springs, and convert the brakes to a dual master cylinder and front disks. Should keep me busy next spring! Couple pics...
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