I'm Back! '90 GTUs
 

So a few months ago I sold my 86 Base. I put quite a bit of work into that car but it was just time for it to go. Since then I've been looking pretty hard for another project and a couple weeks ago I found the GTUs. As much as I didnt want another red FC I made an exception because of what it is.

The interior is pretty clean but its missing the factory radio and came with a garbage Sony head unit that i took out on the drive :smilielol5: It obviously has some rattles and squeaks that ill go through an find.

The body is mostly straight. It does have a baseball size dent in the driver fender and some hail looking damage on the roof and hood. Paint is faded on the mirrors and the rear bumper pretty badly. But I'm not so worried about that at this point. The only really disappointing thing is that it doesn't have the TII wheels on it right now. The guy i bought it from says they are in storage because they had rotted tires on them but he will meet me in a couple weeks to deliver them.

Mechanically it seems fine so far. I has a reman engine in it that i was told has around 30k on it. I drove the car all the way from Greenville, SC back home (Murfreesboro, TN) and didnt have any issues. I guess we did have one scare. I was in 5th and accelerated a bit and it cut power 2 times. That was about 200 miles into the trip and it never happened again. Once we got close to home i was a little harder on it and it has plenty of power and pulls nicely. One annoying thing was that the exhaust seems thrown together... it feels like its rattling pretty bad under the car and its unnecessarily loud. So that will be one of the first things to go.

Also i noticed that it shudders a bit in 1st gear. Im not really sure what thats about but it seems like its revving/accel fine in all the other gears.

A coolant flush is also on the list of things to do immediately. I checked the overflow tank this morning and it looks pretty dirty.

More photos of the car.

Two more. You can see where the VIN was restamped as one of the 100 '90 GTUs models.

Very cool! I always wanted a GTUs but couldn't find one. How does the 0.8xx:1 5th gear and 4.30:1 final drive feel compared to the Base? God Mazda's paint sucked back then.

.756 od

Well to be honest with you it's hard to really say since it has been so long since I drove my old one. But it does feel like it has more pep in 5th.

Wow never seen a VIN restamp myself...


-Ted

Planning to black plastic dip my side mirrors. Id rather them be black then the nasty faded red that they are now. I actually had one started but it got knocked over and messed up. So I'm going to have to peel it off and start over.

I went ahead and placed an order today for a Mazdatrix short shifter, new shift boots and a 93 knob. I took the shift panel off to find all the inner boots missing. Next thing i do will probably be exhaust so i can drive it in peace lol.

Alright so I have the mirrors done. Im not really a fan of black/red combo. But i like them black better than i like them faded.

Also, I just ordered the S5 black off plate kit.. so just the ACV and BAC. I've read mixed things about removing the pump on the S5. I removed all the emissions on my S4 and just wired the 6th ports open and didnt experience any issues. I'm assuming i can do the same on this car.

I've also located my vibration problem... The split air tube is like 9 miles long and isnt anchored to anything so it just bounces around down there. You can also see how shoddy this exhaust is. A full RB exhaust is on the list to do after i have the coolant system flushed.

One more thing... I believe i mentioned in the opening post that i was getting some shuddering in 1st gear (after I'm off the clutch). Anyone have any insight as to what could cause that? The rest of the gears feel fine.

Whats the total mileage on the car? The first thing I'd look at is the driveline mounts. I'd guess it would be the trans mounts, diff mount, or the driveshaft has some slop.

Congrats on the GTUs, in a bout of sacrilege I parted out my '89 GTUs a few months ago. I stalled on the project and was never going to get it on the road in a reasonable amount of time.

Hands down the best mod I did to the car was having an NB Miata gear set put into the S5 N/A case. It made the car so much more fun to drive.

It has about 135k on the body. The engine has around 30k (supposedly). With the way the gear shift feels (like a floppy sausage) my guess is that the trans is original to the car. Is there any reason why it would be limited to just 1st gear?

Thanks man I'm really excited about it. Im ready to kind of run it hard but i want to get the coolant flushed first and maybe have the trans fluid done too. Why the miata gears though? The gearing in this car is already shorter compared to the other models.

You're right. I was thinking of the Miata gear ratios.
Only 5th is shorter in the GTUs. The Miata gear ratios are closer together than the RX7 ratios, even the GTUs, but 1-3 are taller. Source:https://www.mazdatrix.com/g1.htm.

Looks like my power steering rack is leaking...... Boo. I like that it has power steering but knowing that it's leaking I wonder if I should just take the pump out and depower it. Driving with no power steering didn't really bother me in my 86..... But that was also a manual rack.

It's not too hard to rebuild. Bri-bri can walk you through it.

I found his thread on de powering it. Seems like a pain but I don't think I want to shell out the money to try and fix it or have it repaired.

So you just sourced Miata trans and had someone do the input shaft mod for you? Does the fc shifter still fit the same way since it's just the internal parts being changed?

Turns out my weird shuddering is happening in more than just 1st gear. On my drive to get coolant flushed i noticed it quite a bit. Although it seemed to come and go in later gears. It leads me to believe that maybe something is loose. It feels like most of it is coming from under my seat.

The mod is essentially putting the Miata gears into the RX7 transmission housings so the rear housing and shift linkages are still all RX7. Though technically you could swap some Miata stuff over so you could run a Miata short shifter if you wanted. They're much cheaper for some reason. It sounds straightforward but it's a pretty complicated task. You have to completely disassemble the transmission to get to remove the input shaft. I posted a how-to on here a while back detailing the process per the FSM.

Describe the 'shudder'.

Like the engine is missing? Clutch chattering? Suspension shunt?

A good local standup guy (in Northern VA that is) is selling a NA FC trans with the Miata gears on it. I don't want to cross post threads, but if you are interested, I can get you in touch with him (or pm you his FS thread)

I have those injectors and new connectors if you want them. You cover shipping and they are yours.

its more of a heavier vibration coming from under my butt. I looked on Mazdatrix and actually found a trouble shooting guide for that sort of thing. I've basically narrowed it down to bad u-joints, trans mounts, or bad ring and pinion (crap i hope not because those are pricey). So i started cheap and ordered the trans mounts. Ill just work my way up from there until I've replaced it all.

Feel free to post the link here or PM me. I may not be in a position to buy it now but I'd love to know the price. Or see if i can work out a deal with him.

Heck yeah Ransom. Text me 406-450-4103.

Texted ya. I will get them ready to send out Monday. I will just ship them and we can figure it out. If I get an address

Ransom you da man!

Have you inspected your trans mounts? Most likely they're bad considering the age and exposure to oils which turns them into a mushy mess. I've seen this on a few 2nd gens. I've had some completely separate.

Good choice, if you don't have the aluminum shield for the mount closest to the exhaust I'd recommend getting it.

Yeah I'm hoping that will make a difference. I'm not sure about the shield though. It looks like all that is still present but i could be wrong. Its been so long since I've been under one and worked on it that I'm having to re learn a bunch.

Just to elaborate more on my inspection yesterday. I laid under the car for about an hour or so just looking around at stuff, trying to move it, etc. Nothing was obviously loose or easily moveable. Bushings are obviously worn which I'm sure is a contributing factor to the vibes I'm getting.

Bushings will be coming soon as well but i figured trans mounts would be a better first place to start. I ordered a new trans brace as well. I'm contemplating dropping the trans and just cleaning it up when i do the mounts. Its just nasty and has what smells like gear lube on it but I didnt notice any leaks. I guess it would be a good idea to drain it and refill as well. If i do drop the trans.. is there anything else i need to do before i put it back in?

get snot slinging drunk.

There will be bolts missing if that happens!

If it's trans mounts, it'll make a LOT of noise on shifts...
Anything from a thud to a BANG during the shift is your typical sign of failure.

It's uncommon that bad trans mounts induce a shudder during driving though, but this could be a symptom of something else...


-Ted

It could be a clutch or throw out bearing.

Indeed.

I was reading up on Mazdatrix about similar symptoms. now that you've said this though i guess ill have to think about something else. Trans mounts should be here in a day or two. I told them a joke in the comments section and they (Himni) upgraded me to 1 day shippings because i made them laugh haha.


I guess thats getting added to the list to then. So even though its happening when I'm off the clutch it could still be either?

wiggle the shaft to check for u-joints and backlash



giggitty

Wouldn't you rather me wait until you're around for me to wiggle the shaft? :suspect::smilielol5:

PMed with Tracking Info...

Thank you Bae! I even included dielectric in the clips..:rofl:

youbetcha!:tongue1:

Ugh.
Their stuff is crap...


-Ted

Well that would have been nice to know. What's to bad about their stuff? Seems like it would be kinda hard to mess up a poly mount.

got the trans mounts in the mail, short throw/bushings, inner shift boots and new knob will be here today. I'll probably go ahead and put that in. Now I'm just waiting for the new trans brace to come in and then ill do the mounts and see how everything feels.

Since I've started driving it leaks seem to be getting slightly worse so it looks like ill need to do the oil pan gasket and brace next.