Gearbox Oil Log Out | Topics | Search
Moderators | Register | Edit Profile

Australian RR Forums » Silver Shadow Series » Gearbox Oil « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Francis
Frequent User
Username: jackpot

Post Number: 328
Registered: 11-2016
Posted on Thursday, 02 April, 2020 - 08:35:   Edit PostDelete PostView Post/Check IP

Hi All again
Wishing you are all safe and well.

My 1974 Silver Shadow, SRH 17968 has the 3 speed gearbox which has always used Dexron oil. Over time this has gone from Dexron to Dexron2 and now to Dexron3 without any issues.
I have done a bit of research and have discovered the diffrence between normal and Dexron oil etc.

The question I have is that my gearbox goes into gear very well and very smoothly, both into D and into R, when the car has just been started even with the revs up high due to the automatic choke. still being on.

But when she has warmed up, she becomes very slightly cluncky going from N into D, but more so into R.
This makes me think that the gearbox works more smoothly if the oil is slighlty thicker, but there is no option of choosing a thicker or thinner Dexron oil, as we can with engine oil viscosity.

Has anyone experienced the same thing? Does anyone have any opinions or suggestions on it?
Thanks
Top of pagePrevious messageNext messageBottom of page Link to this message

Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 613
Registered: 05-2016
Posted on Thursday, 02 April, 2020 - 09:31:   Edit PostDelete PostView Post/Check IP

Hi Patrick, I have three ideas regarding the cause of your clunky gear selection when the engine is warm compared to the smoother gear selection when the engine is still relatively cold and all these theories could well be wrong:
1) The ATF level is too high causing too much pressure when the fluid expands as it heats up and/or
2) Your radiator fins may be clogged and/or your viscous fan might be worn out which would reduce the radiators cooling effect on the ATF causing the transmission oil to overheat. The ATF circulates through the bottom portion of the coolant radiator. This would be more apparent if the car is idling in situ rather than being driven on the road when air would be pushed through the radiator. If this is the case you should notice your engine temperature rising higher than usual when the engine is running while the car is stopped and
3) Your engine revs may be set a little too high which would cause the gear selection to be more clunky especially when the ATF is hot.
Top of pagePrevious messageNext messageBottom of page Link to this message

Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 614
Registered: 05-2016
Posted on Thursday, 02 April, 2020 - 09:37:   Edit PostDelete PostView Post/Check IP

then of course there's the obvious possibility that the ATF and filter may be due a change.
Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Francis
Frequent User
Username: jackpot

Post Number: 330
Registered: 11-2016
Posted on Thursday, 02 April, 2020 - 16:45:   Edit PostDelete PostView Post/Check IP

Hi Larry
Thanks for that, but all points are good. I change oil and filter on the gearbox every 5 years or so, last change 6 months ago, and used a good Castrol Dexron3.
ATF level is good.
Viscous coupling new 18 months ago and works very well. Also checked and cleaned and serviced all rads when I did this, including the little pipe that cools the steering fluid.
Engine idles at 700ish when warm - but a lot higher when cold and gear changes are smooth as silk with thicker colder oil......
Top of pagePrevious messageNext messageBottom of page Link to this message

Martin Taylor
Experienced User
Username: martin_taylor

Post Number: 180
Registered: 07-2013
Posted on Thursday, 02 April, 2020 - 17:55:   Edit PostDelete PostView Post/Check IP

When the oil is cold it takes longer to go through the selector valve and engage the clutch in the gearbox so there will always be a difference.
Your idle should be 600, a little higher when A/C is on if a compensator is fitted.
Soft engine mounts or diff mounts can cause such issues as the torque throws everything in the other direction when reverse is selected.
Get someone to move the gear lever for you and check to see how much movement you have in all the mounts etc
Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Ryan
Grand Master
Username: patrick_r

Post Number: 2215
Registered: 04-2016
Posted on Friday, 03 April, 2020 - 01:15:   Edit PostDelete PostView Post/Check IP

Hi Patrick,

My 72 Shadow SRH12255 had exactly the same issue.
At high RPM with the choke on, it just slipped beautifully into gear, D or R.
A problem with the vacuum supply to the modulator, was an issue, and a newer type of modulator was fitted. Problem solved.

I canít remember exactly what modulator was fitted, plus all paper work went with the car when I sold it.

Mine was sorted by the local auto trans specialist.
But any auto trans specialist who knows the very typical GM Turbo Hydro 400 fitted to these cars will sort it immediately. .
Top of pagePrevious messageNext messageBottom of page Link to this message

David Gore
Moderator
Username: david_gore

Post Number: 3655
Registered: 04-2003
Posted on Friday, 03 April, 2020 - 07:30:   Edit PostDelete PostView Post/Check IP

Re the GM Turbo 400 - don't overlook the fact RRMC had these transmissions modified from the normal GM specification by the fitting of a "wave" clutch plate to allow some "slip" when the clutch activated to give a "smooth" gear engagement commensurate with Rolls-Royce standards.

The downside was the clutch plates had a life of around 95,000 miles before they had to be replaced due to noticeable slippage and "slurred" gear changes.
Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Francis
Frequent User
Username: jackpot

Post Number: 331
Registered: 11-2016
Posted on Friday, 03 April, 2020 - 07:40:   Edit PostDelete PostView Post/Check IP

Thank you all - very interesting information. Iíll be having a look over the next days and keep you updated. Modulator vacuum pipe probably first stop.
Top of pagePrevious messageNext messageBottom of page Link to this message

felipe heuser
Experienced User
Username: felipe

Post Number: 98
Registered: 07-2017
Posted on Monday, 06 April, 2020 - 05:42:   Edit PostDelete PostView Post/Check IP

I always thought engaging a gear when revs are high would damage the transmission; hence always wait until warm with normal idling...
Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Ryan
Grand Master
Username: patrick_r

Post Number: 2219
Registered: 04-2016
Posted on Monday, 06 April, 2020 - 06:17:   Edit PostDelete PostView Post/Check IP

Felipe,

My car slid into gear so silky smooth at high idle forward or reverse. It was amazing.

Just disappointing when it was hot it would bang horribly into gear.
Top of pagePrevious messageNext messageBottom of page Link to this message

David Gore
Moderator
Username: david_gore

Post Number: 3658
Registered: 04-2003
Posted on Monday, 06 April, 2020 - 08:05:   Edit PostDelete PostView Post/Check IP

Patrick,

This is not normal - I would suspect a sticking valve spool in the valve body for some reason when the transmission is hot. Another possibility could be a failed O-ring on the top of the fluid pick-up tube from the fluid pan.

I will have to dig out my T400 overhaul book to see if you can remove the valve body after removing the oil pan without having to drop the entire. transmission.

Replacing the O-ring is a simple but messy job after removing the full pan unless you have fitted an after-market drain plug [highly recommended].

Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Francis
Frequent User
Username: jackpot

Post Number: 332
Registered: 11-2016
Posted on Monday, 06 April, 2020 - 14:29:   Edit PostDelete PostView Post/Check IP

Thanks Daviid - Iíd appreciate that.
Top of pagePrevious messageNext messageBottom of page Link to this message

David Gore
Moderator
Username: david_gore

Post Number: 3659
Registered: 04-2003
Posted on Monday, 06 April, 2020 - 20:00:   Edit PostDelete PostView Post/Check IP

Patrick,

Have attached a copy of the B&M Guide to rebuilding the Turbo 400 Automatic Transmission - this involves removal of the transmission from the vehicle however it also covers strip down and rebuilding the individual components after they have been removed from the transmission.

There is a good guide to possible causes of transmission problems on pages 24 and 25 plus a list of tools and parts needed on page 26.

I have also enclosed Section T from Workshop Manual TSD2476 and refer you to pages 143 to 308 which covers the Turbo 400 3 speed torque convertor transmission. Unfortunately almost 25 years have elapsed since I overhauled the T400 transmission and my memory is hazy on the details and I cannot rely on it to advise you in more detail.

application/pdfB&M Instructions
B&M T400 Overhaul Instructions.pdf (13620.8 k)


application/pdfTSD2476
T Automatic Transmissions.pdf (68046.6 k)


Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 2286
Registered: 09-2004
Posted on Monday, 06 April, 2020 - 21:47:   Edit PostDelete PostView Post/Check IP

Nothing that a good workout will cure.
That's the rolling done with the roller.
LPG running well.

Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Francis
Frequent User
Username: jackpot

Post Number: 333
Registered: 11-2016
Posted on Tuesday, 07 April, 2020 - 04:13:   Edit PostDelete PostView Post/Check IP

Hi David
Thanks for those. Things are not bad enough to delve into frightening territory yet, but I have downloaded and saved the documents just in case..........!

Patrick - I hope you remembered to engage 4wd!
Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 2287
Registered: 09-2004
Posted on Tuesday, 07 April, 2020 - 04:38:   Edit PostDelete PostView Post/Check IP

Patrick, the ground is dry as a bone, looks like another drought this summer.
BTW the LSD is still working well if the ground gets soft, ground clearance would be a problem though.
Top of pagePrevious messageNext messageBottom of page Link to this message

ross kowalski
Prolific User
Username: cdfpw

Post Number: 1349
Registered: 11-2015
Posted on Tuesday, 07 April, 2020 - 09:26:   Edit PostDelete PostView Post/Check IP

Patrick L,

That has to be in my top five "Rolls Royce used as a farm implement" pictures, heck, maybe top three.

Also, you have LSD?, I didn't even know that was an option
Top of pagePrevious messageNext messageBottom of page Link to this message

Stephen Bardwell
New User
Username: cobard71

Post Number: 9
Registered: 03-2020
Posted on Tuesday, 07 April, 2020 - 09:31:   Edit PostDelete PostView Post/Check IP

Mssr rolls and royce are spinning in their graves about now I fear.
Top of pagePrevious messageNext messageBottom of page Link to this message

ross kowalski
Prolific User
Username: cdfpw

Post Number: 1350
Registered: 11-2015
Posted on Tuesday, 07 April, 2020 - 10:00:   Edit PostDelete PostView Post/Check IP

As I recall in the original film, Max was driving a semi tanker?....Hmmm.

Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Ryan
Grand Master
Username: patrick_r

Post Number: 2220
Registered: 04-2016
Posted on Tuesday, 07 April, 2020 - 20:24:   Edit PostDelete PostView Post/Check IP

Terrific photoshopping mate.

That was the second movie Ross.
Top of pagePrevious messageNext messageBottom of page Link to this message

Patrick Francis
Frequent User
Username: jackpot

Post Number: 334
Registered: 11-2016
Posted on Wednesday, 08 April, 2020 - 03:12:   Edit PostDelete PostView Post/Check IP

LSD? May not be found on the car, but a lot of it being smoked at the moment by the looks of things.

Add Your Message Here
Post:
Bold text Italics Underline Create a hyperlink Insert a clipart image

Username: Posting Information:
This is a public posting area. Enter your username and password if you have an account. Otherwise, enter your full name as your username and leave the password blank. Your e-mail address is optional.
Please quote Chassis Numbers for all vehicles mentioned.
Password:
E-mail:
Options: Enable HTML code in message
Automatically activate URLs in message
Action: