Mazada 5 speed gearbox spacer feedback anyone?

[CtrMint]

Afternoon All, 

I'm finally on the way to rebuilding my 420R rear end having had a nightmare with various diff carriers.  I ended up fitting the carrier from my original diff.  At the moment I've only got the Dedion and radius arms in along with the diff, so figure now is the time to fit the gearbox spacer.

Before I do fit the spacer, I thought I'd seek feedback.  How many people have given it a go? Does it really help reduce noise, especially when reversing etc?  Anyone fitted it and found it makes no improvement.

Please no Tracsport comments.

Thanks

[ScottR400D]

Ah the old Mazada box!
 

[ScottR400D]

ChrisC will have sure info but as far as I have am aware it only corrects location errors and stops things touching on chassis rails etc. 

There is/was a thought that it might improve the parallel location of the box and diff but further thought on that would suggest that the amount it lifts the box would be insignificant. 

Having said that it probably can't do any harm either. 
 

[CtrMint]

It's a special edition don't you know, comes with an extra racing strip.  

[Geoff Brown]

Is Tr**s**rt not to be mentioned because you might eventually succumb to having one fitted.

You know it makes sense 

[7 wonders of the world]

Are you sending the 'new' unused BMW final drive back to CC then.....

....you could then rebuild yours with a LSD from Steve and still have a pocket full of dosh....

[CtrMint]

no guys, I'm fitting the new titan from CC as planned.  I'm then going have my original diff assessed to see how bad if any the damage is.  if it's beyond repair, then I'll bin it, if it's serviceable then I'll service it.  In the event it is beyond repair then I'll likely get the Tracsport when the new one fails or I repeat the same process.  Of course, since I now have a usable 620R, who knows what might happen.  I might loose interest in the 420.  

Anyways I'm getting mixed views on the spacer via Instagram,  can anyone offer some input from experience?

[ScottR400D]

Have you asked CC what the spacer is designed to do and why? 

[ChrisC]

I have it in writing from CC, it was added for clearance between the chassis and the gearbox.  If you think that statement through, that means clearance is marginal without it, something that's been known for some time.  Given the price and how easy it is to fit, for me it's a no brainier, on any pre 2021 5 speed Mazda boxed car, especially if your working on the car in that area.

That said, the reason it dramatically reduced my cars noise wasn't because of clearance, it was because it altered the prop working angle slightly, which combined with a faulty front UJ meant a reduction in noise and vibration.  Ultimately my car was only fixed of vibration and unexplainable noises with a prop replacement.  
 

Given your diff was out, you did check your UJs didn't you?

[ScottR400D]

#7 what makes you think there's a risk of the original being 'beyond repair'? 

I'm not aware of any units that have failed beyond repair.  

[CtrMint]

Have done, awaiting a response, but in the meantime thought I'd seek feedback here.

[CtrMint]

Thanks Chris, appreciate the input, sounds like a thumbs up.

I haven't got that far into the reassembly.  Diff is in, but the drive shafts and hubs aren't in yet.  

The hubs and bearings seem fine, no issues with play or smoothness etc.  I've not really checked the drive shafts UJs.   What did you find with yours?

I noted from your blog that high speed driving caused vibration.  While mine hasn't been on circuit, living on the IOM gives the opportunity to get north of 100mph (legally), and there's no vibration.  I just have the usual slow speed maneuvering noise, and the on and off torque clonk, which I assume is just backlash.

[ScottR400D]

The prop shaft with its U/Js is the shaft from the gearbox to the diff. You can't check them properly with the prop out, so it's too late if the diff is back in. Having said that failure is rare in my experience, at least at low mileage. 

The drive shafts don't have U/Js. 

[ChrisC]

The vibration was very distinctive, speed related and was felt in the seat.  All the signs should have pointed me to prop, but basically I put it off hoping for the simplest solution.  The interesting bit is the noise also sounded like diff, but wasn't (or was it).  With a front UJ no longer identifying as a UJ you get strange changes in rotation speed of the prop entering the diff. This must have been loaded and unloading the CWP and diff pin against the ramp angles, especially in reverse where the angle is 90 degrees.
As said UJ failure is rare (first I have experienced), and had my car been outside warranty a swap to a better quality UJ would have been my desired route, but while under warranty a replacement prop was the answer.

[ChrisC]

Sounds like you haven't got the same problem as my car had :-).  You would know it. 

[7 wonders of the world]

My prop on my previous car was toast after about 3000 miles front joint foooked, had new joints fitted both ends by a local prop guy who builds them for many race guys, MUCH better quality ones and rebalanced, had the  prop in my current car overhauled in the same manner too as the OE joints used are built to a price point   

[CtrMint]

I suspect the 420R will be going to Mr Dangerfield at Southcoast for a corner weight session once my new Penske 7500 are installed.  I'll ask Paul to review the prop while its there, see if there's any issue from a professionals touch..  At the end of the day, my replacement diff process is entire precautionary.  It's not like I had a significant deterioration in road manners, I wanted to service it now (5000miles) so that I didn't push the distance between a refresh.

With regards the spacer.  I'm going to fit this weekend, when I drop the oil from the gearbox. I'm not expecting a miracle.

Out of interest does anyone know the size of the fill plug on the gearbox?  I'll need to get some tube before hand.

thanks

[ChrisC]

If nobody knows of the top of their head, it might be worth speaking to the gearbox manufacturer (or converter) since the casing is their design not Mazda.  https://www.vitesse-ltd.com/