fivestar

I have an 88 Iroc convertible and just recently I hear a loud "clunk/thunk" from the right passenger rear of the car when I my automatic changes into second gear. It seems it only happens when I 'get on it'. If I am driving normal I do not hear it at all. The sound is a clunk/thunk, I know my Ujoints need replacing and they sometimes make a clicking sound mostly when I am backing. This new sound makes me think something is going to breakaway an axle or something in the suspension...Any thoughts or experiences from other third genners? I have raised up the car and looked around but don't see anything out of place-the car is completely original with the original bilstein shocks and suspension and still handles very well with no squeaking or creaks at all save for the occasional ujoint. Any insight would be much appreciated.

Fivestar

red rock

iTrader: (2)

Check the tranny mount, you will have to push up on the tranny and look at the mount for separation. Bad u joints that are clicking is trouble if, "you get on it."

IROCZ1989

iTrader: (1)

U joints...change them then let us know.

Edwardgp

novaderrik

the exhaust could be clunking against something.. worn out sway bar end link.. worn out control arm bushings.. worn shock bushing or mounting bolt.

the only way to know for sure is to get under your car and see if anything is moving that shouldn't be moving.

fivestar

I have already checked the trans mount and it is still solid. I will be changing out the Ujoints in the next couple of weeks-if not I will do them over the winter when the car is in the garage/stored for winter. Though I have raised up the car and visually checked everything....you all are right I need to get under the Iroc with wrenches and check to see if everything is tight and no broken bolts throughout the suspension and all attaching points. I have a half day off coming up and will keep you all posted with what I find underneath.
The car runs great and is soooo reliable, hasn't thrown a code in about the last two years and I have driven it back and forth to Arizona and Idaho a couple of times during this period, I just want to insure I take care of the maintenance-thanks for the insight!

Fivestar

BMR Tech

The exhaust is most likely the culprit as that is the location of the over-axle pipe. The rear heat shields have a tendency to come in contact with the exhaust and create an annoying noise. Anywhere from a vibration all the way to a loud thud. I would check that out.

- Kevin

fivestar

Well got the car up and looked all around grabbing this and that along with taking some tools and checking to see if anything was loose or not bolted down, everything is tight. Looks like my next step is to go ahead and replace the U-joints, since I knew they were worn after nearly twenty five years I hope that will solve my clunking sound-will be able to get to that next week and will let you all know if that fixes things.

Fivestar

IROCZ1989

iTrader: (1)

Depnding on what you do with the car look into the splicer solid sealed units and get the driveshaft balanced while the shop has it. Trust me get a driveshaft shop to do this for you. I had a repair shop do ujoints on a truck I had a while back and the u joints walked out of the cap and took out the tailshaft on the tranny. Have a reputable driveshaft shop swap these and make aure you use torque wrench on rear caps, i think its 22ft/lbs. Take care.

fivestar

Thanks that is solid advice and a quality driveline shop here in Colorado Springs can do install the Splicers for about $70. The Ujoints have been there nearly twenty five years and since the car is staying in the family (car is going to my daughter in a few years) I know the new ujoint will last at least another quarter century...

Fivestar

TTOP350

iTrader: (8)

Prolly should have a peek at the spare tire area also, to see if anything is loose.

rarebmx

iTrader: (6)

same issue here but ONLY when I get on it from a dead stop. I just lowered the car and never had this issue until after that. U-joints were not even in my thoughts, I thought tranny mount....

fivestar

Yea I cannot figure it out...I did check the spare wheel area last night and tightened up everything just in case but the loud 'thunk is still present on hard acceleration when changing from 1st to 2nd. Gotta be the u-joints. I am going to try one other thing before I replace the u-joints and that will be to get the entire car on jackstands and place take a video of the car changing gears to see if I get any movement... wish mew good hunting

Fivestar

Edwardgp

And be sure to keep us informed.

IROCZ1989

iTrader: (1)

Yes please do. I feel if it is the u joints( and I feel it is) when you pull them see if you can inspect for hairline cracks. Most of the time you cant see the cracks when there mounted in the straps. Take care.

fivestar

Well I did put the car on jackstands and placed the car in gear but since there is no resistance on the driveline the car does not shift as it would with the wheels on the ground so no good feedback there.
I did get the Ujoints replaced and everything buttoned up and the clicking noise the ujoints had been making the past few years is now gone. I am thinking that it just might be my Trans mount even though it looks solid I do not have a long enough pry bar to check if the rubber has separated. It is an inexpensive part and easy to remove and replace...Next on my list and I will let you know in a couple of days.

Fivestar

red rock

iTrader: (2)

Trans mount is under $10 and easy to replace.

fivestar

Was able to take care of replacing the Trans mount today...Yup that was it! The "clunk" is now gone!! It took me all of about twenty minutes and took it for a test drive and happy to report no extra sound. I get home though and I am leaking like all getout! Coolant squirting out the side of the water pump onto the driver side rail! Get the car up in the air and look from underneath and see the gasket on the waterpump is leaking/squirting...
Wow! To be honest the car has given me so few problems since I rebuilt the engine and trans nearly eight years ago that I am actually thankful that I have had only a handful of issues with the nearly 25 yo daily driver. I am going to go ahead and replace the water pump since I have to tear down the front portion of the engine to get to the water pump and gasket-going to replace a couple of the hard to get hoses while I am there...wish me luck.

Fivestar

rarebmx

iTrader: (6)

Glad to hear the issue. I didn't think the u-joints would last "clunking" under that much torqe for very long. Mine has to be tranny mount too by the location of the noise.

fivestar

Trying to attach a couple of photos of a Jasper Built TPI Engine I planned on putting into my 58 Chevy that is in the background. as you can see I polished the top end and it even has a fivespeed trans to go behind it. Hope the pics come through...

Fivestar

red rock

iTrader: (2)

Nice looking motor. What is the rated HP and TRQ? Nice job on the polish too.

fivestar

I pulled the motor out of an 89 Iroc donor car and contacted Jasper out in Indiana about the Class II build and they told me that with their build and by replacing the 19lb for 22lb injectors and the addition of headers I should be running about 350 HP and about 350+ ftlbs of torque at the flywheel and I have to say I drove the car a bit before dismantling it ran like a scalded ape.

Fivestar

red rock

iTrader: (2)

That's a nice street build.

fivestar

Thanks to all who followed the Clunk fix. I did also fix the coolant leak. Instead of just replacing the gaskets I went ahead and replaced the whole water pump and while I was there I re-installed my factory oil cooler. I have fixed the "clunk' by replacing the Trans Mount and replaced the old clicking ujoints and fixed the sudden gasket leak (took the time to flush the cooling system) on the water pump while getting a chance to get the factory oil cooler back in and change my oil (wanting to keep the car original)-been a pretty good week!
Thanks for all the suggestions.

Fivestar

Edwardgp

Yep you were kicking butt.

fivestar

Thought I would post a few pics of the car that kept me hopping these last couple of weeks. I am the third owner and it is an Arizona car (previously owned by one of my brothers) built in the factory in California. In December I replaced the soft top with one that has real glass rather than plastic. No rust anywhere though it does need paint... Hope you enjoy the pics.

Fivestar