Upgrading my UN1 in a GTD

[Eric]

Hello

After driving my newly acquired GT40, and dealing with the issues present in the UN1 that it came with. I have decided to get a new transaxle and put the UN1 out of its misery (and mine).

The car in question is a GTD replica, powered by a 347ci V8 with Holley 4150 carbs. The car also has a transmission cooler. CTQ 443.5 lbft at @5000 and Cpower 483.89 HP @6500. The Car is RHD and RHS.

I am thinking about going for a ZFQ but wanted to hear opinions about other options that I could look into. The shifting experience in the UN1 with the cable shifter it came with was extremely frustrating. I'm looking to upgrade the transmission to have a reliable, smooth and hassle free transmission. No sticky gear shifting and finicky shifting experience would be possible. The car being RHD RHS, I'm not sure any non cable solution exists.

I do not plan to race this car but can drive it pretty aggressively under the right conditions.

Can anyone with a RHD RHS GT40 recommend a reliable and satisfying transaxle/shifter solution? Is the ZFQ (with whatever shifter options they provide) reliable and precise?

Thanks

 

[Mike Pass]

If the transaxle isn't broken then just change the shift mechanism. The GTD cable one is not good. Most people fit a rod change setup.
Cheers
Mike

 

[Eric]

If the transaxle isn't broken then just change the shift mechanism. The GTD cable one is not good. Most people fit a rod change setup.
Cheers
Mike

The UN 1 has internal problems it seems. It won't shift into the right gears at all. Sometimes position 1 is third and sometimes it's first gear. It almost never shifts into second. And going into reverse is a gamble. Gears 4-5 cannot be shifted into either.

Thought it was a calibration problem with the cable shifting mechanism but it seems it is an internal problem with the gearbox.

If anyone knows a good shop in the US that is willing to have the car shipped over and really go into details about what's wrong I'd love to get recommendations.

At this point I do think it's best to get a new transaxle and shifting mechanism.

 

[Mike Pass]

It still sounds like a change mechanism issue. The symptoms you describe can be attributed to the vagueness of the gearchange mechanism. Check the shift at the box. Remove the mech and try changing the gears with a visegrip clamped directly on the shaft at the box. I suspect the box is OK and the cable mech is worn/badly adjusted. The Renault UN1 boxes work well and last well. Mine is still good after 20 years of hard use in my GTD. The only negative is that the gearchange is a bit slow. The boxes are not hard to rebuild/upgrade. I have a manual in pdf format - drop me a PM if you want a copy.
Cheers
Mike

 

[Eric]

It still sounds like a change mechanism issue. The symptoms you describe can be attributed to the vagueness of the gearchange mechanism. Check the shift at the box. Remove the mech and try changing the gears with a visegrip clamped directly on the shaft at the box. I suspect the box is OK and the cable mech is worn/badly adjusted. The Renault UN1 boxes work well and last well. Mine is still good after 20 years of hard use in my GTD. The only negative is that the gearchange is a bit slow. The boxes are not hard to rebuild/upgrade. I have a manual in pdf format - drop me a PM if you want a copy.
Cheers
Mike

Would you be able to recommend a reputable shop in the US that would be able to sort this out? I bought a cable shift kit for the UN1 to replace the existing shifting in case it's that.

If it's not the shifting mechanism the next step would be to upgrade the transaxle.

 

[Mike Pass]

I don't know any shops in the USA as I am in the UK. I think the logical way forward is to swap out the change mechanism as you will still have to do this if you put a different transaxle in. You may find the Renault UN1 is Ok with a better gearchange setup. If you are still unhappy then you will have the new mech installed ready for the box change.
Cheers
Mike

 

[Malcolm]

GTD cable shift problems are caused by a couple of potential factors. Heat damaging the cables as directly under the silencers so insulate this area. Also ensure you have Heim joints on both ends of the cables as they are way more precise.

If you still want to change the transaxle then the ZFQ is meant to be good. Its the change up I would go for. I have the Souhern GT solid shifter upgrade on my car with UN1 installed at the same time as lowering the engine with the Southern GT frame conversion. This is very very worthwhile and the handling is greatly improved. Souhern GT also used to do a ZFQ frame conversion for the GTD with solid shifter. With the effort to install a solid shifter set up for any gearbox, the effort is worth it to drop the engine at the same time IMHO.

AK have taken over the Southern GT set up now so worth talking to them. Any decent chassis guy should be able to weld and adapt your GTD it is not overley complicated just need competancy at welding and fabrication.

 

[Morten]

I doesnt look like AK will sell any parts, nor make any chassis modifications as per SGT rear suspension.

 

[Randy V]

Something else to watch for with any cable driven things is cable retention. If, when you’re moving the shifter, the cable housing moves (even a little), the housing needs to be restrained at that point.

 

[Malcolm]

AK seem very happy to quote me for rear suspension uprights and parts to upgrade my GTD items.

 

[Morten]

AK seem very happy to quote me for rear suspension uprights and parts to upgrade my GTD items.

Thats brilliant, hope they will follow up and deliver