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Old 08-12-2019, 11:10 AM   #1 (permalink)
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Default New to us 3000GT needs work, where to begin...

My son just picked up a 1992 3000G VR4 for cheap and, naturally, it has a long list of issues needing to be addressed. Some are not that big of a deal (I mean, how critical is it to replace a power radio antenna in 2019?) but others seem as though they need to be addressed right now.

This car was an auction car so a reliable service history is non-existent. Hell, any service history is non-existent. Oil looks fresh but that's cheap insurance so that's on the list as is a 60K service. We haven't looked at the timing belts yet but I know how detrimental a failed timing belt on a Mitsubishi engine can be (Had a 1990 2.0 Plymouth Laser and a 1992 Eagle Talon TSi AWD and both had a timing belt slip at 30k trashing the valvetrain each time...) so I want to make sure that gets done soon. Also, it has the infamous lifter tick that we'll eventually need to address.

However, there are a couple other issues that seem like they could be equally critical. The first is there is a big clunk in the rear when shifting or whenever the drivetrain is "wound up"...ie if you let of the gas...clunk...then get back on the gas even though you didn't shift...clunk. I've read here that there could be a number of things that cause this from carrier bearings to sticking driveshaft joints, to diff backlash adjustments. He plans on getting the car on a lift and do the driveshaft check to see if the diff backlash is within spec but if that looks good, I'd hate to have him spend money on carrier bearings if it's a driveshaft issue. Any tips on diagnosing which possible solution to pursue first?

Also, above about 60 the car begins to shake. The steering wheel shakes as well. I've read where this can also be linked to a driveshaft with frozen or stuck u-joints. We have eliminated tire pressure or loose lug nuts from the equation and found a couple tires lower on pressure. Correcting that helped but only very little. He plans on throwing the car on an alignment rack at his work (he's a lube tech for a local GM dealership) and the tires on a balancer to eliminate those possibilities but the vibration feels more like it's coming from the car and not the wheels/alignment.

Another issue he's having is the transmission popping out of 4th on occasion and out of reverse all the time. Reverse is so bad he doesn't even have to start letting out the clutch before it pops out. If he doesn't hold it in reverse it won't stay in. From what I've read here, it sounds like a linkage issue and considering it is fine in 2nd, sometimes comes out of 4th, and won't stay in reverse, it sounds like the linkage may be out of adjustment or hitting something since it is only affecting the "lower" gears (lower in the shifting pattern that is) and gets worse left to right.

I have read on here one owner had the linkage hitting on his lower radiator hose. This car has a Koyo radiator and...I measured across the top of it and this sucker is 2.25" thick so not sure if this is the same 1.5" thick core that 3SX sells...I wonder if this thick radiator could cause this kind of interference. If not, any suggestions on how best to check linkage to see if it needs to be adjusted and if this may fix the issue?

I have also seen that the clutch pedal being out of adjustment could cause this. I have downloaded the service manuals from 3SX (what a treasure that is...) and KIND of got a feeling on how it's done but would this miss adjustment cause this kind of issue?

Finally on this issue, I've seen mention of gear nuts that can come loose in the transmission (I know my terms are absolutely crap...) that can be accessed by removing the passenger side wheel liner but I've read that this issue is generally connected to 5th gear popping out. Is there something there that may be causing this? I realize it could just be it's time to dig into the trans but I would like to eliminate any issue that could cause it that doesn't require dropping the trans to fix it first.

We've only had this car since Friday night so excuse my ignorance if I've missed very obvious topics that thoroughly cover these things. I've searched and read as much as I can find but it is a bit overwhelming (not to mention looking into other things such as fixing the Active Aero, Active Exhaust, and Electronic Suspension...) so any direction on what to tackle first would help.

He has about $400-500 every other week (or so) to spend on repairs so managing what to budget for first is important.

Any advice on where some of these components are or what exactly I'm looking for would help too. I'm not even sure where things like the shift linkage is on the transmission itself or if I need it on a lift to check this...or pull of parts to access it...so any advice like this on checking these things would be a huge help.

Sorry for the long post but there is a lot here we're dealing with and I've done my best so far on searching for posts and videos covering these questions as best I can. I don't have a ton of automotive experience except for a couple specific platforms. (GM W-body and Kappa platforms)

Thanks for reading all this and for any assistance you may be able to provide.
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Old 08-12-2019, 06:29 PM   #2 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

Getting access to the shift linkage is quite simple. It's on top of the transmission just below the intake pipes. You'll want to pull out the Y pipe connected to the throttle body (has a vac line at the firewall and the blow off valve hose on the bottom,) the filter box, MAF and intake bubble that splits to the two torbos.
From there you should have ample access to the linkage, no lift required.
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Old 08-12-2019, 10:31 PM   #3 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

Thanks PhailosaurusRex, that's exactly what we needed.

My son got his car on a lift today and said the driveshaft was way out of spec. It rotated between 1/16th and 1/8th of a revolution. I'm guessing this is responsible for the thunk and vibration at speed.
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Old 08-12-2019, 11:47 PM   #4 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

My buddy used to run an auction house, and one of the smiley things they would do is change out the oil and clean any gunk under the oil cap if there was any to hide a blown head gasket.

I don't have the VR4, but based on guesstimate of your issues you have the following problems:

The clunk in the back you're hearing is your differential slipping, most likely from a warn clutch pack or broken spider gears. If it's a BIG clunk, it's most likely a spider gear is broken. If it's a low vibrating clunk, it's probably the clutch pack.

Shaking is probably from a bad suspension. Does the car bounce when you press on it?

Transmission sounds like linkages problem. Unless it's grinding or making weird noises, it's probably the linkages.

It sounds like you know what you're doing, all of the things you mentioned are pretty solid in terms of what could be wrong with it. Not really sure what else we can do other than speculate based on what you said without seeing the car. Have you taken it to a shop yet?
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Old 08-13-2019, 09:39 AM   #5 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

We have a friend that specializes in JDM cars...has a R32 and R33...he did a quick glance at it but we're going to have him go over it in a bit more detail.

I checked the oil when we bought it, no signs of contamination. Also checked it again a two days after to see if all looked well. Coolant looks good too. If there is any kind of issue in the heads, they've hidden it well. I don't put it past folks to use those coolant leak repair products to get a car through, you know? Hopefully that's not the case here.

The clunk is a big one. I would think if we had a busted tooth though it would be more recurring wouldn't it and not just under throttle transition? Also, would that account for the excessive driveshaft play? Whatever it is, it definitely feels like it's in the diff region.

Haven't given it the bounce test yet but I have a truck with 250k miles on the shocks...they are shot...and it doesn't vibrate like this. This feels more like an alignment or something out of balance.

I appreciate those insights. It's actually exactly what I'm looking for...alternative ideas to the ones I've already found or input on the ones I've mentioned as to what it is specifically I'm looking for to diagnose the issues...like PhailosaurusRex letting me know where the shift linkage is in the engine bay.

That engine bay is so tight I worry I might tear off the entire top end just looking for a fuse box. LOL SO much better if I know where they put this stuff. You can tell Tetris was popular when they put this car together. LOL
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Old 08-13-2019, 10:18 AM   #6 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

First place I would look for your clunk is the front/rear roll stop motor mounts. Very common failure, and when they aren't doing their job, everything moves around...

Get the FSM... There are multiple places you can download it. Several of the vendors have them on their sites, Mitsubishilinks.com, the other forum, etc. Good information is key to working on the cars.

Get to know stealth316.com ... Jeff put together an amazing site that's been the the go-to for 3S knowledge for many years.
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Old 08-13-2019, 11:19 AM   #7 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

I've seen the motor mounts for sale but I saw them listed as Upper front, upper rear, lower front and lower rear (I think it was front and rear...maybe left right...I have to go back an check). Are the roll stop motor mounts part of these four motor mounts or are they something completely different?

FSM I am assuming is the shop manual? I downloaded the two volumes 3SX has on their site. I'll look at Mitsubishilinks.com too. And thanks for the link to stealth316.com...I'm not sure I've ran across that site yet.
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Old 08-13-2019, 12:51 PM   #8 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

Quote:
Originally Posted by Robotech View Post
I've seen the motor mounts for sale but I saw them listed as Upper front, upper rear, lower front and lower rear (I think it was front and rear...maybe left right...I have to go back an check). Are the roll stop motor mounts part of these four motor mounts or are they something completely different?

FSM I am assuming is the shop manual? I downloaded the two volumes 3SX has on their site. I'll look at Mitsubishilinks.com too. And thanks for the link to stealth316.com...I'm not sure I've ran across that site yet.
roll stops are the front and rear mounts, although I've never heard of there being upper and lower. there are only four mounts as far as i've seen. one on the driver side by the timing set, one in front, one off the trans, and one off the back. do the 'ol stab the throttle and watch for the motor hoppin routine for that.

fsm is shop manual, yes, and stealth316 is gonna be more than your best friend, you're gonna wanna marry that site lmao. if you ever read something in the shop manual and get confused, check stealth316, and he's prolly got a whole essay on it that'll clear everything up. tbh stealth316 is probably more useful than the FSM

did you check for wheel weights? out of balance wheels can cause vibration through the steering wheel and are a cheap fix.

as for the clunking, sounds like you've got a pretty good idea of what to check so far, and it does seem a lot like when my driveshaft shat the bed. you may also wanna check the rear diff bushings too, I think I've heard of people having similar symptoms when those go out.

two solid tips I can give in regard to the driveshaft is to make sure you have the proper amount of fluid in the tcase after you re-install it, and DONT let a shop touch it unless they have prior experience with the platform. I got to learn those two together when I had a shop rebuild my driveshaft
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Old 08-13-2019, 01:43 PM   #9 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

Thanks for all that. I am use to GM shop manuals and they are written so someone, like me, that knows the difference between a box end wrench and a ratchet wrench are and not much more can figure out what to do. This one seems to ASSuME you know more about automotive maintenance. If stealth316's site is as you describe it, I'm going to need to go out and get another set of wedding bands and the fiancÚ is just going to have to understand. LOL

Yea, I figured out later I got the names of the mounts all wrong. LOL

I haven't looked under the car but I figure all his mounts are shot...both the engine mounts and the diff carrier mounts. I made sure he added these to his "I need to get these sooner than later" list. Top on that list is figuring out this clunk and the shaking. Second is the 60k service.

He works at a GMC dealership as a lube tech and he has access to a tire balancer so he was going to check that tomorrow when he has time after work to do so. Told him to throw it on their alignment rack too because I know that can cause these kinds of things as well.

Last edited by Robotech; 08-13-2019 at 02:13 PM.
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Old 08-13-2019, 08:48 PM   #10 (permalink)
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Default Re: New to us 3000GT needs work, where to begin...

So, a bit of an update.

I got to drive the car for the first time today and we diagnosed a couple of things.

The gear popping out issue. The car has a Koyo radiator in it and when we put the car in reverse, or any of the lower three gears...2nd, 4th, or reverse...it felt like there was a spring trying to push it out. A quick look under the hood and sure enough, that linkage was pushing into the lower radiator hose. Now to do some research on how others moved that out of the way as it looks like my routing options are limited.

Next was the problem getting it into gear and some stall/starting issues my fiance had trying to drive it. I was looking up the issue about it popping out of gear and someone mentioned adjusting the clutch pedal. I read up on that and all the adjustments that can be made along with what some of the measurements should be. The main one I noticed was how much distance there should be between the firewall and the top of the pedal at the point where the clutch fully disengages. Its supposed to be 2.2 inches or more...this clutch starts to engage as soon as you take pressure off it. So that needs adjustment.

We also revved the engine and while it moved some, it wasn't a huge amount. The mount by the timing cover looks good but really didn't check the rest. Not sure how much it should move when it gets revved but it seems like it is moving more than it probably should...but no shaking at idle or anything like that.

More to come, thanks for the help.

Last edited by Robotech; 08-13-2019 at 09:11 PM.
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