Hey everyone. This is my first post on this site. i just recently got an 87 Iroc. It used to have a 305 but now its got a 350. Theres as expected a few issues but the major issue i have with the car is a really bad vibration at speeds 60+. Now from what i can tell it seems like the driver side door isnt closing right. im almost 100% sure thats the porblem. Has anyone experienced this problem? if so what can i do? its depressing to have a car like this but cant go past 60mph lol. Another problem im having s with the fans. they wont ****in turn on. changed the relays and even the harness and nothing. itll turn on when i jump it with no problem. on the radiator i noticed what apears to be a sensor/switch but there isnt a wire anywhere that could connect to it. i dont wanna blow my motor already so i really wanna try and figure this out. what could that be and what can i do. and one last thing. Didnt all the irocs come with a limited slip? only my pass side wheel spins. its annoying man. the car was originally a 305 auto and it has drums

 

anyone?

 

The door bushings are probaly worn out and need replaced. 60+ vibrations are probaly worn out front steering/supension components (find a good alignment shop they should tell you whats worn out) Use the search tool to find post on the fans. dont know about the posi.

 

unless the previous owner rigged the car together, there is a fan switch in the passengerside head, between the rear two cylinders. that turns the fans on. If you pull the plug of it, 1 wire plug, and ground out the wire, the fans should turn on. If they do, the fanswitch is bad and you need a new one. If it still doesnt turn on, you need to keep tracing wires.

 

That's only half the story. There are two fans. One is controlled by the ECM and turns on first. The other is controlled by the switch in the head and only turns on when it's about to self-destruct (243F as I recall). A lot of people just wire one to come on with the ignition rather than troubleshoot it. Not my style, but a good short term solution.

 

Not to question your integrity, but are you sure your tires are all balanced, even a tiny imbalance on the wheels can be exacerbated at higher speeds. As for the posi rear, to double check if it still has a posi rear in it, look at the pumpkin, on the bolts that hold the rear axle cover on, there should be a metal tag on one of the bolts that says "use limited slip diff lube only", if it is indeed a posi, then try changing the rear fluid, and if that doesnt work, the clutches in the posi couldve started going bad. Good luck!

 

i think it could be the tires arent balanced properly, i just recently picked up a 96 grand cherokee and the thing vibrated like crazy at 100km and the steering wheel was crooked, the tires on the front were fairly bald so we replaced them and problem solved (the tires were either warped or imbalanced) and the steering wheel is straight.

 

well it does need some front end work. but ive never seen a car shake so violently as this does because of the front end. you can actually hear the door shake on the driver side. my girl said if you look close you can actually see the door shake. thats why im almost 100% sure its the door. i know the front end is only making it worse but im pretty sure the biggest reason is because of the door. as far as the door bushing how hard are they to replace? ive never had to place those before on any car. if it is the clutches in the rear for the lsd then ill throw some better gears in there while im at it. im a little hesitant to go with 3.73 because it is my daily driver and im on the highway a lot. ill probably get them anyway. im guessing with the lsd fixed, i should be able to run a 14.6 or so. with the gears, headers y pipe and exhaust whjat could i expect? 14.2's or so?

 

lets not forget that our drive shafts have been known to cause alot of shake or vibrations in cars at high speeds, i went through alot to find out that was my problem