I'm Back! '90 GTUs

[project86]

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 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.

[project86]

More photos of the car.

[project86]

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

[RETed]

Originally Posted by project86

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

Wow never seen a VIN restamp myself...


-Ted

[infernosg]

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.

[project86]

Originally Posted by infernosg

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.

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.

[C. Ludwig]

.756 od

[project86]

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.

[project86]

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.

[MolotovMan]

Originally Posted by project86

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.

[project86]

Originally Posted by MolotovMan

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.

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?

Originally Posted by MolotovMan

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.

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.

[infernosg]

Originally Posted by C. Ludwig

.756 od

You're right. I was thinking of the Miata gear ratios.

Originally Posted by project86

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.

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.

[project86]

Originally Posted by MolotovMan

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.

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?

[infernosg]

Originally Posted by project86

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?

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.

[project86]

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.