Reverse on Jatco Auto Box ;
 

R75 1999 2.0 Petrol . Connie 80k miles.

The Symptoms' are; All forward gears OK, no issues. Reverse non operative.
Select reverse and there is a slight "jolt" indicating the selection appears to work. On one occasion during the icy weather it did work but after a short run went back to previous non-op conditions; and on another occasion after a 5 mile run the reverse did select but it didn't last.

On the flat there is a very slight movement in reverse but that's it! it stops after a few feet. No change despite increasing engine revs.

I have replaced the reverse gear set that included the piston cylinder, and all clutch plates etc, although previously used for a very short period, was reported to be of the revised Cylinder type and working. It did have some dirt from the previous use but a session with the parts washer cleaned that up.

There is of course no guarantee that the replacement was working 100% but as the symptoms with the replacement are the exact same as the original, it would appear that there may be an underlying cause.

As I write this my colleague is making up a tool for the press to be able to release the circlip on the clutch plates of the original cylinder, for curiosity if nothing else.

It would appear that selection works, but insufficient thrust on the clutch plates.

Can anyone shed some light where to check next please. Thank you for reading this.

This thread may have some useful information but some of the pics appear lost:-
https://the75andztclub.co.uk/forum/s...d.php?t=155169

I may help you...
 

Hi Chuck:

I'm the one who wrote the thread Mike is referring to, I have the photos I posted on that occasion. Maybe they'll serve as a reference for you to compare the components you've changed and the result. The symptoms you have now are very similar to mine several years ago.

Best regards.

Joel Antonio

Hello Joel,
I have PM'd you your documents so if you could include photos that would be great and most helpful.

At present I am in the process of making up tooling to fit on my press in order to release the circlip of the reverse cluster to get to the piston. The replacement I bought in, was a complete unit so no need to split the old one, however my thoughts now are to inspect the old one to see if it did have a split

I think I did it with a wooden dohnut and a g-clamp, it's only to compress the spring so no special tooling required as such.

Ive seen this phenomenon before in person and the trouble you've got is your symptoms aren't linked with reverse piston failure. Although your cars the correct age, this problem has appeared a few times now and it hasn't been diagnosed. I suspect you'll find nothing wrong with the reverse piston assembly and the problem will remain once the gearbox has been rebuilt....

Oil pressure is leaking somewhere, but not at the reverse piston because a tell tale of that failing is you loose 5th and 4th gear as well. I think the problem may lie within the valve block, possibly a non return valve passing or an actuator not functioning correctly even though it is "technically" working.

Edit, I've properly re-read your post to discover you've been in and replaced the reverse piston assembly. Yes there's an underlying problem but the remedy isn't known yet.

As far as I am aware all forward gears work fine, well they did on the original gearbox set up, just reverse failed. After a decent hard run abut 4-5 miles reverse worked for about 400-500 yards, on and off, also after starting up on a very cold morning. With the replacement set of reverse gears the symptoms were exactly the same as previously; leading us to the conclusion that either the replacement, or the original had the same issue.

The replacement one I acquired had been fitted to another vehicle for a very short time and was declared OK as they too had multiple issues. The set was then removed and I took it from there. I don't have 100% proof that the replacement was perfect - only say-so. Hence the need to split the original gear cluster (as it is handy and out of the gearbox) and examine the piston, for own peace of mind at least.

I have the car up for sale but do not want to sell in the present condition, but if all else fails and I am running out of time, it may have to go as is.

Have you checked the solenoids' resistances - preferably whilst warm? I know little to nothing of gearboxes, but have read that fluid issues can be caused by solenoid failures.

Post 4 gives you the figures.