I'm Back! '90 GTUs

[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.

[knonfs]

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?

Originally Posted by infernosg

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.

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)

[chibikougan]

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

[project86]

Originally Posted by djmtsu

Describe the 'shudder'.

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

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.

Originally Posted by knonfs

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)

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.

Originally Posted by chibikougan

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

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

[chibikougan]

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