Reverse gear - grinding noise

...Check the Adjustment on the 'Back-Up Light' SWITCH.
If it is Screwed IN TOO FAR, You will have That Problem, because that prevents the Shift Rod, 'In the Gearbox', from moving as Far LEFT as it Needs To, in order to Engage Reverse, Smoothly! And You WILL 'Grind Gears!'. Yes! The Biggest Mistake some have made. is Assuming the Reverse Switch should be Screwed ALL the WAY IN!

Also, if the Gearbox is 'Coasting Down' from Another Gear, that will make it 'Grind', While Shifting into Reverse. With the Engine still running, Vehicle at a 'Stand-Still', with the Clutch DIS-engaged, try Engaging 1st or 2nd gear, Before trying to go into Reverse, to drag the gears to a stop, and THEN try engaging Reverse.

The way to adjust the Switch is, ofcourse, put the shifter into Reverse, don't forget to turn on the 'Key'....and Screw the switch in until the Back-Up Lights come On! But, then Move the Shift handle sideways (while still in reverse) and see if you can Make the Lights go OFF. They should stay on with the Shifter AT REST, with the Vehicle Backing Up! If they go off, that could be Dangerous for You!

Grinding going into gear is usually related to insufficient clutch release. Check your clutch adjustment first.

Interesting. I have similar symptoms. I'll try the reverse light thing

Thanks very much for the interesting comments.
I had checked yesterday evening the clutch adjustment. I could very easily turn the clutch friction disc a few degrees with disengaged clutch (with screw driver through clutch hole). I think to my opinion this is an indicator that the clutch is properly disengaging but I'm not at all an expert on this.....
I had already tried to put first and second gear in before going into reverse....but unfortunately with no positive effect.....
I will check this evening the screw position for the reverse switch...would be fantastic if the issue could be solved so easily.....

Brgds

Hartwig

I checked the 'Back-Up Light' SWITCH. I removed it completely and it had no positive effect.
Brgds
Hartwig

You need to measure the clearance you have between the clutch disc and the flywheel/pressure plate.

On the three finger you NEED to have about .045" as I recall. The diaphram will put up with .035".

If you don't have that, it is likely the problem.

Having said that though, if you aren't operating the clutch pedal fully, then you have the same issue.

Don't put a carpet mat under the pedals.

Sig, some owners have had positive results with Redline diff lube. But it is a thinner fluid with less shock resistence than the recommended (and thicker) 80W90 lube ZF originally specified. If it grinds more- or sooner after warm-up, go back to stock lube. And if all external adjustments don't help, its possible there is enough metal worn away inside the ZF that the shifting will always grind a little, until an overhaul is done. This is, after all a 43-year-old performance sports car and things DO wear out!

Note that if this is whats really needed, all new parts come from RBT Transmissions in Southern California, who bought the design rights from ZF 30 years ago. All other ZF-fixers either buy their parts from RBT or cannibalize other ZFs for useable bits. You can also talk to your local 911 Porsche owners; their transaxles are (I think) built under license from ZF and often have the same problems.

Thanks for all that good feedback. Meanwhile I checked the clearance between flywheel and clutch disc. The clearance is well above 0.05" but I found that with the clutch fully disengaged there is still some friction noise between flywheel and clutch disc. I was suspecting that the clutch disc was not freely moving on the gearbox shaft and keeping still a bit of contact with the flywheel. I decided to put brake cleaner into the clutch hoping to wash out deposits from the gear shaft. That worked to certain extend and I can now into reverse without noise provided I had the gearbox stopped before with the first gear. I also realised that I can very easily move the clutch disc with disengaged clutch and the gearbox in neutral which demonstrates that with the red line oil the gearbox moves without much resistance. That means that already a very light contact between clutch disc and flywheel is enough to get the gearshaft moving thus resulting in noise when putting in the reverse gear. It is probably a good idea to go back to the 80W90 gearbox oil.
Brgds
SIG

quote:

Originally posted by SIG:
Thanks for all that good feedback. Meanwhile I checked the clearance between flywheel and clutch disc. The clearance is well above 0.05" but I found that with the clutch fully disengaged there is still some friction noise between flywheel and clutch disc. I was suspecting that the clutch disc was not freely moving on the gearbox shaft and keeping still a bit of contact with the flywheel. I decided to put brake cleaner into the clutch hoping to wash out deposits from the gear shaft. That worked to certain extend and I can now into reverse without noise provided I had the gearbox stopped before with the first gear. I also realised that I can very easily move the clutch disc with disengaged clutch and the gearbox in neutral which demonstrates that with the red line oil the gearbox moves without much resistance. That means that already a very light contact between clutch disc and flywheel is enough to get the gearshaft moving thus resulting in noise when putting in the reverse gear. It is probably a good idea to go back to the 80W90 gearbox oil.
Brgds
SIG

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Hartwig,
It is NOT a good idea to go back to the original lube. Leave the Redline 75w-90NS gear lube in the box!!! Do not be swayed by peoples opinions that do not work on these ZF transaxles every day.Use the Redline please.....

Bonjour,
Just to let you know that the noise issue on my gearbox is fixed now. It was related to the clutch disc not freely moving on the gearbox shaft (was solved by brake cleaner) and the replacement of the master cylinder that felt okay but was not providing full performance.
Brgds
Hartwig

You just sprayed brake cleaner in there? Through which opening? Or did u remove the ZF first?

Sig, there are two subtly different input shaft sizes in Panteras, by year. The clutch discs also vary. The spline on the early shaft is 1-1/16, 12 tooth (same as the Mangusta) while the later shaft is 1-1/8, 12 tooth. Most people cannot tell the 0.030" OD difference by looking at the shafts & matching discs- you must measure with precision tools.

It is possible to bolt an early clutch together with a late disc and it will function while rattling and possibly cocking sideways in operation. Adding an early disc to a late clutch assembly will be very tight if it assembles at all. I am always amazed by the ingenuity of non-Pantera mechanics in making things work that should never meet.

Another source of sticking is the throwout bearing (two models of those, too!) which slides on a steel ZF nose-piece. Wear sometimes raises a ridge on the underside of the replaceable tubular nose. Be sparing with any grease or solvents you put in there on the nose-piece and/or input shaft splines. If it somehow gets into the clutch, a perfect clutch may begin to slip under heavy load & cannot be restored, only replaced.

The input shaft on the -1 ZF is a bit shorter than the -2 and they are both 10 splines.


Ron