Go Back   The 75 and ZT Owners Club Forums > The 75 and ZT Owners Club Forums > Technical Help Forum
Register FAQ Image Gallery Members List Calendar Search Today's Posts Mark Forums Read
Notices

Reply
 
Thread Tools Display Modes
Old 8th September 2021, 00:11   #1
ardenconny
Newbie
 
Rover 75 Saloon

Join Date: Aug 2021
Location: Kuusamo
Posts: 7
Thanks: 0
Thanked 9 Times in 3 Posts
Unhappy Jatco transmission issues

Hello everybody,

Itís sad really that my first message here has to be a negative one. Anyways, I have a serious issue with my 75 Jatco box. This saga started a few months back in may, when I acquired a beautiful -99 75 Conny with a blown reverse belt. My mechanic happily changed it for me and for a while the car worked like a dream (unlike my 45 haha). But then, some problems started to appear.

When I start driving with a cold engine, the gearbox is REALLY sloppy, like it needs 3-4k revs just to start slowly crawling ahead. Surprisingly, reverse gear works just fine. After a while, assumingly when the gearbox has warmed up, the box works just as usual. When the box is warm, itís smooth as butter and it works very well. However, last Friday it REALLY left me down. I went to pick up groceries, the box being sloppy as usual, but this time, it really did not want to move. I gave her like 4-5k revs (I didnít dare to give it more) and then it triggered limp mode. Triggering limp mode did not make the car move at all. After a while sitting, the box continued it usual sloppiness and drove ďfineĒ for a half-mile, then everything stopped working. Limp mode continuously came on and off, the car did not move forward nor reverse at all. I had to tow it (yes stupid idea) with engine running to just to get it back home. I figured that if I keep the engine running and gear in neutral, maybe it doesnít do too much damage.

Since then I have tried to read fault codes from the box via Toaf, but thereís none. I even had issues connecting to the box in the first place. Me and my mechanic are astonished. I think that maybe there are connecting issues due to my old nasty coolant leak. The upper coolant hose under the airfilter box had a rupture on it and it was spewing coolant right to the top of the gearbox, maybe thatís causing the connection issues???

But I seriously wonder why the box became so sloppy all of the sudden. When the renovation was complete, me and my wife took the car for a nice long trip without any gearbox issues. After we returned, then the box became all sloppy (thatís when the hose ruptured too). I wonder could it be because of the oil my mechanic used? He said that he used Comma MVATF+ oil and deemed it to be compatible, is it really? He now says that the gearbox issues could be because of gearbox valves or solenoids are getting stuckÖ?

I work in IT and my mechanic is not really that familiar with the Jatco autobox. He used to take very good care of my 45 and 600 so thatís why I still use him. I hope thereís someone that could give me and my mechanic a nudge to the right direction

Ps: We do not have access to a T4 system, the closest t4 to me being over 500 miles away, and with a broken gearbox I obviously canít reach it.
ardenconny is offline   Reply With Quote
Old 8th September 2021, 07:53   #2
SD1too
Doesn't do things by halves
 
SD1too's Avatar
 
Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model.

Join Date: Mar 2007
Location: Middlesex
Posts: 18,181
Thanks: 1,222
Thanked 3,261 Times in 2,800 Posts
Default

Hello Samu and to the club.

I'm not quite sure what you mean by a "blown reverse belt" but I take it that your mechanic replaced something in the automatic gearbox.

Here is the data sheet for Comma MVATF+ and it doesn't meet the MG Rover "N402" specification. However I doubt that the fluid could be responsible for such a severe malfunction. I think it's more likely that the gearbox has been underfilled (raising the revs being necessary to achieve the correct fluid pressure).

If you're not able to work on the car yourself my suggestion is that you find an automatic transmission specialist who can drain the fluid and replace it with a type which meets N402 spec. As the JATCO has no dipstick, someone who knows the procedure is essential particularly as the level checking plug is on the bottom of the gearbox casing!

Simon
__________________
"Whatever is rightly done, however humble, is noble."
Sir Henry Royce.
SD1too is offline   Reply With Quote
Old 8th September 2021, 08:57   #3
MissMoppet
Gets stuck in
 
MissMoppet's Avatar
 
R 75 Tourer diesel, V6 Conny

Join Date: Mar 2013
Location: Taunton
Posts: 737
Thanks: 191
Thanked 280 Times in 156 Posts
Default

Before a real expert comes along humour me with what I've done for refilling the Jatco box. I know you're supposed to drain the whole box and carefully run it for seconds through each gear to expel the old fluid. I decided some years ago that I would drain and replace with the approved fluid from here till it reached the drain plug hole knowing full well that two or so litres would be left in. Run it for a few miles, up on the ramps, drain and fill as before thus diluting the mixture of old and new. If I was feeling wealthy I would do that again so that the original old fluid would be an insignificant proportion. It may not be strictly kosher but it's worked for me on my 150,000 mile Diesel Tourer. My own local garage - whom I trust - said they would not dare run the Jatco near dry and I got the impression that pretty well all garages would only drain and replace what they could more or less in the same manner.
__________________
Rover 75 Tourer CDTi 2004 remapped 160 auto, R75 V6 2.5L auto Connoisseur 2003
MissMoppet is online now   Reply With Quote
Old 8th September 2021, 09:15   #4
vitesse
Posted a thing or two
 
Rover 75 Saloon

Join Date: Jul 2011
Location: Gšvle
Posts: 1,949
Thanks: 325
Thanked 661 Times in 533 Posts
Default

The correct spec of oil is available at Biltema: https://www.biltema.fi/autoilu---mp/...ljy-2000041561

Do a bit of research and I think you'll find that the Jatco transmission was used in lots of other cars too, so it's not as uncommon as you might think.

Regards
vitesse is online now   Reply With Quote
Old 8th September 2021, 11:50   #5
ardenconny
Newbie
 
Rover 75 Saloon

Join Date: Aug 2021
Location: Kuusamo
Posts: 7
Thanks: 0
Thanked 9 Times in 3 Posts
Default

Hello and thank you for the helpful answers. The part that my mechanic replaced was the brake band back in May. I am a little bit sceptical about the biltema oil, as Iíve had bad experience of being their customer in the past. It does list JATCO N402 as supported, but Iíd need some sort of clarification on that. Would the oil replacement really be the saving grace for that box?


Sent from my iPhone using Tapatalk
ardenconny is offline   Reply With Quote
Old 8th September 2021, 12:23   #6
vitesse
Posted a thing or two
 
Rover 75 Saloon

Join Date: Jul 2011
Location: Gšvle
Posts: 1,949
Thanks: 325
Thanked 661 Times in 533 Posts
Default

Quote:
Originally Posted by ardenconny View Post
Hello and thank you for the helpful answers. The part that my mechanic replaced was the brake band back in May. I am a little bit sceptical about the biltema oil, as Iíve had bad experience of being their customer in the past. It does list JATCO N402 as supported, but Iíd need some sort of clarification on that. Would the oil replacement really be the saving grace for that box?


Sent from my iPhone using Tapatalk
Sure some things from Biltema are poor substitutes like track-rods, but can they really fake the specs of their oil? A Norwegian poster (Beinet1) used the same Biltema oil. Link: https://the75andztclub.co.uk/forum/s...=122171&page=4

Issues connecting to the box with Toaf sound familiar, a Swedish owner very recently had problems too and found a blown fuse. Does Toaf connect, or does it report module not found?

Regards
vitesse is online now   Reply With Quote
Old 8th September 2021, 12:50   #7
ardenconny
Newbie
 
Rover 75 Saloon

Join Date: Aug 2021
Location: Kuusamo
Posts: 7
Thanks: 0
Thanked 9 Times in 3 Posts
Default

Quote:
Originally Posted by vitesse View Post
Sure some things from Biltema are poor substitutes like track-rods, but can they really fake the specs of their oil? A Norwegian poster (Beinet1) used the same Biltema oil. Link: https://the75andztclub.co.uk/forum/s...=122171&page=4

Issues connecting to the box with Toaf sound familiar, a Swedish owner very recently had problems too and found a blown fuse. Does Toaf connect, or does it report module not found?

Regards
Toafís connection is very very finicky. Sometimes it finds modules, sometimes not. Sometimes it reports an access violation as well. The connection issues however are no way exclusive to the Jatco box either, so maybe that needs more investigation. Iíll look into the fuse and Biltema oil
ardenconny is offline   Reply With Quote
Old 8th September 2021, 13:43   #8
vitesse
Posted a thing or two
 
Rover 75 Saloon

Join Date: Jul 2011
Location: Gšvle
Posts: 1,949
Thanks: 325
Thanked 661 Times in 533 Posts
Default

Sorry couldn't remember earlier but then lightbulb moment. I believe he had no indicator of the selected gear, found fuse 4 had blown and most of his problems vanished (he's just confirmed fuse 4 engine bay fusebox).

I am a big fan of Toaf, use it a lot more than my T4 as I find Toaf 100% reliable. As you're in IT you might find it interesting that I use a RS232 lead rather than USB. I don't understand the difference but I tried a USB one and quickly reverted to the serial lead (WinXP).

Good luck
vitesse is online now   Reply With Quote
Old 8th September 2021, 20:08   #9
COLVERT
Foreign correspondent
 
COLVERT's Avatar
 
R75 Saloon.

Join Date: Feb 2009
Location: France/or Devon.
Posts: 13,112
Thanks: 3,548
Thanked 1,923 Times in 1,622 Posts
Default

Quote:
Originally Posted by SD1too View Post
Hello Samu and to the club.

I'm not quite sure what you mean by a "blown reverse belt" but I take it that your mechanic replaced something in the automatic gearbox.

Here is the data sheet for Comma MVATF+ and it doesn't meet the MG Rover "N402" specification. However I doubt that the fluid could be responsible for such a severe malfunction. I think it's more likely that the gearbox has been underfilled (raising the revs being necessary to achieve the correct fluid pressure).

If you're not able to work on the car yourself my suggestion is that you find an automatic transmission specialist who can drain the fluid and replace it with a type which meets N402 spec. As the JATCO has no dipstick, someone who knows the procedure is essential particularly as the level checking plug is on the bottom of the gearbox casing!

Simon
Being the curious type I discovered that Kuusamo is in Finland.---
__________________
COLVERT is offline   Reply With Quote
Old 8th September 2021, 20:43   #10
MSS
This is my second home
 
Rover 75 CDT - selling

Join Date: Dec 2007
Location: Suffolk
Posts: 5,548
Thanks: 30
Thanked 68 Times in 48 Posts
Default

Quote:
Originally Posted by COLVERT View Post
Being the curious type I discovered that Kuusamo is in Finland.---

Likewise
MSS is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 22:28.


Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Copyright © 2006-2020, The Rover 75 & MG ZT Owners Club Ltd