Stripped rear diff gear - solutions?

[The Doctor]

Hi guys, bought a lightly-used (standard) ZX5 recently and have so far raced it a couple of times. Really pleased with it, but tonight I stripped the rear diff gear. The grip was high (fresh grass, Ballistic greens) with some fairly large ramps, but I'm still a bit surprised. It was shimmed fairly tight but free running.

Is this a common problem with the ZX5?

Solutions I can think of:
1. loosen the slipper
2. full ali motor/input shaft mount
3. 3-racing ali input shaft collar for the rear gearbox.

Any advice?

Cheers,
Paul.

[niggs98]

as you say loosen the slipper. mine was always set for 2-3 foot of slip. i used to shim the diffs tighter than kit. from memory i used to use 3-1 rather than the kit 2-2. the gear box will feel slightly notchy when you first build it but will free up after 1-2 runs. give that a try. make sure you have the newer diff halfs as these support the diff gear better and reduce the flex in it as well

[jim76]

yeah shimming it tighter than kit sorted mine out fine. And as Niggs said make sure you have some slip from the slipper, never lock it up.

[burgie]

the big problem I found/find with ZX5 diffs is that they really don't like the brakes being applied....if you can avoid having to "hit" the brakes hard the diffs last well.

if you have full-time 4wd on a lazer, they make the original pred gearboxes look strong!

[DanW]

Yep, I agree with Burgie on this one.

If you run full 4wd and like to jam on the brakes then you need to shim it tight.

I run one way on the shaft, and set the speedo up for gentle brakes, and my diffs are loosely shimed for free running.

I've only ever stripped gears from braking, or landing a jump badly with loads of power or brakes on.

[The Doctor]

Thanks guys, I think it's a combination of slipper too tight & shims. It was shimmed 1-3 rather than 3-1 (ie looser than 2-2).

2 questions Mr Niggs:

1. what's the part # for the newer diff halves?

2. are you or do you know Stuart Rand?

Cheers.

[niggs98]

thay were sold as a running change on the zx5 about 2 1/2 years ago so prob have the standard part number. it will be simple to see if you have them. if your diff ring sits inside the diff halve (supported from inside back and outside) then they are the newer style. if it looks like a losi one (ie just supported from the back and inside only) then it is a older one.

i also used to run diff front and back and a one way prop as that used to reduce the problem as well

i know stu as race against him quite often in my regionals.

[RogerM]

Originally Posted by burgie

the big problem I found/find with ZX5 diffs is that they really don't like the brakes being applied....if you can avoid having to "hit" the brakes hard the diffs last well.

if you have full-time 4wd on a lazer, they make the original pred gearboxes look strong!

What a load of crap!!!!!!!!

I always, no matter what the car, shim the gearboxes so there is no backlash between pinion and crown when check with a light load against the crown wheel to push it away from the pinion (as the forces would do when the car is running).

I built my original ZX5-SP like that and NEVER touched the diffs on a car that was run a huge amount, on all sorts of surfaces and jumps with up to a 4.5 in it!!!!

The ZX5 transmission is almost bullet proof if built correctly!

[Colinevan]

Originally Posted by RogerM

What a load of crap!!!!!!!!

I always, no matter what the car, shim the gearboxes so there is no backlash between pinion and crown when check with a light load against the crown wheel to push it away from the pinion (as the forces would do when the car is running).

I built my original ZX5-SP like that and NEVER touched the diffs on a car that was run a huge amount, on all sorts of surfaces and jumps with up to a 4.5 in it!!!!

The ZX5 transmission is almost bullet proof if built correctly!

Ha ha lmao... Hmmmm chill my good man lol.

Burgie has himself bought a few zx5's as so have i , I see many zx5's retiring with nasty gearbox noises here oop north lol. I myself had one of the first zx5's when they first came out and with a 5.5r in it used to last one day at southport.

With experience it was shown that shimming tight would aid matters, but in itself it was a big problem. I read that the main problem was the plastics ( this was changed at some point ). the gearbox housings front and rear, used to strip quite easily when having a few front end knocks. this in turn meant that the clamps on the shaft bearings were not tight allowing very small movements of the diffs, big jumps or bumpy track with many braking corners put maz strain onto the zx5, and in the end i sold up and changed car.

Many zx5 owners experience this.

Col.

[DanW]

Originally Posted by RogerM

What a load of crap!!!!!!!!

I always, no matter what the car, shim the gearboxes so there is no backlash between pinion and crown when check with a light load against the crown wheel to push it away from the pinion (as the forces would do when the car is running).

I built my original ZX5-SP like that and NEVER touched the diffs on a car that was run a huge amount, on all sorts of surfaces and jumps with up to a 4.5 in it!!!!

The ZX5 transmission is almost bullet proof if built correctly!

Err... not crap
You build your car tight to prevent stripping gears, but increase drive train friction = slower, hotter car, but more robust.

If you run front oneway and don't jam on the brakes you can afford to run a much looser drivetrain = speed and efficiency.

But lazer gears not as strong as orignal pred gears, i'll agree.... that is crap!

[burgie]

don't argue with RogerM. He knows everything there is to know about Lazers. Our experience with them doesn't count.

[Fabs]

Well I have to say I'm yet to strip a gear and tbh it seem to me that they are very robust indeed. However this may not be true on the pre-sp zx5 but I couldn't tell you. And it could be a different story with the rtr.

Personally I shim my gears as tight as possible with no biding or tight spot, is with minimal play, did that on my shaft tc back in the days and never stripped a bevel gear on any of my shaft cars.

[The Doctor]

Wow, wasn't expecting such passionate responses, but it's all good advice nonetheless. I'm going to shim it up tighter (I must admit I had it shimmed pretty loose) and let the slipper off a bit - that'll sort it.

Cheers.

[erkan]

well i agree with rogerM here.. if you shim it tight from the beginning it will be tight and sound like crazy for the first couple of packs, then the gears settle in and it will be as smooth, free and sturdy as anything else..

[RogerM]

To qualify my statements I should also point out that I did a full season on one set of gears in my Pred P8 .... it's all in the build and I usually spend a huge amount of time on the build of transmission, easily a couple of hours at each end including freeing up bearings.