| Author | Message | ||
     KC Saayman Prolific User Username: kc_saayman Post Number: 103 Registered: 10-2004 |
Good morning My 1974 Shadow has lost reverse gear. It happened after the car was parked for a few hours in a slight nose down position (pointing downhill) I am not sure if this is of any significance but I thought I’d mention it anyway. When I engage reverse I can hear the clikity-click of the electrical actuator, and can feel the gentle clunk when she engages reverse. However, the car won’t move unless I rev her hard for a short while, then it slowly picks up and gradually moves. My first thought was low fluid, but that checked out OK, in fact, possibly a bit over full (I checked it exactly as described the manual) I then thought perhaps the gearbox filter is blocked, so I dropped the sump and replaced the filter and fluid. Following this when I engaged reverse the car gently drifted rearwards, but there was still no drive. When revving she now does not pick up at all. Note, at this stage I am checking the fluid level cold as I cannot get the car out of my driveway to warm up the fluid. As per the the manual, the level is about 15mm below minimum, which is correct when checked cold. Have any of you experienced this? I did read the trouble-shooting section in the workshop manual, but must confess I find it a bit overwhelming. I also find it confusing as it is not always clear when they are referring to the earlier 4-speed box, or the later 3-speed version, as fitted to my car. I would really appreciate your advice on this. Kind regards KC | ||
| David Gore Moderator Username: david_gore Post Number: 997 Registered: 4-2003 |
Hi KC, When you did the oil and filter change, did you replace the O-ring on the oil pick-up tube? If this O-ring is cracked or missing, air will be sucked into the transmission along with the fluid and cause problems such as you are experiencing. The other possibility is a faulty or worn-out clutch pack which necessitates a full overhaul. This is not too difficult for an experienced DIY owner - the biggest problem is removing the transmission from under the car if you do not have a hoist. Working flat on your back with the car on stands will test your patience and mobility..... See if you can find a copy of the book mentioned in the link below, it is worth its weight in gold when overhauling the T400 3 speed transmission: http://au.rrforums.net/forum/messages/17001/1572.html | ||
| Mark Aldridge Experienced User Username: mark_aldridge Post Number: 30 Registered: 10-2008 |
KC, The first sign of failure on my Shadow 3 speed box was a reluctance to reverse uphill and an Oil leak from the front of the box.Within the next 2000 miles forward changes deteriorated also.I had the good fortune to purchase a new box and torque converter from Crewe at their clearance sale at a very good price .(unfortunately they do not have sales very often) Mark | ||
| David Gore Moderator Username: david_gore Post Number: 999 Registered: 4-2003 |
Forgot to mention the B&M overhaul Kit for the GM Turbo 400 [TH400] can be used for the R-R/B version of this Transmission. The only part that may be needed which is NOT included in this kit is the wave plate in one of the clutch packs [forgotten which one] - this was available as an individual part from a specialist GM transmission parts distributor when I needed one for DRH14434. See the following link for more details: http://www.bmracing.com/PRODUCTS/Buick-Chevrolet-GMC-Olds-Pontiac_3/Buick-Chevrolet-GMC-Olds-Pontiac-65-87-TH-400-375-and-M40 It also includes details of a simple modification to stop the inbuilt clutch slip which accelerates wear of the plates. This modification results in a more abrupt gear change which may not be to the liking of some owners. | ||
| KC Saayman Prolific User Username: kc_saayman Post Number: 106 Registered: 10-2004 |
Thank you very much for all the replies. It sounds like the box will have to come out, which in unknown territory to me. In view of this I will probably leave it to the specialists. However, I do have a shallow pit working area at home, so I could probably consider removing the box and sending that off for overhaul. Is this wise, or should I just let them remove and re-fit the gearbox? When I look under the car it certainly does not seem like a big task to remove it. Its weight and size may present a bit of a problem, but one I believe I can overcome. That book looks interesting David. I love books, so I may just get a copy anyway, even if I don’t intend to repair the gearbox myself. Thanks again for all the advice. I really appreciate it. Kind regards KC | ||
| KC Saayman Prolific User Username: kc_saayman Post Number: 107 Registered: 10-2004 |
David wrote; "When you did the oil and filter change, did you replace the O-ring on the oil pick-up tube? If this O-ring is cracked or missing, air will be sucked into the transmission along with the fluid and cause problems such as you are experiencing" This got me thinking. When I replaced the filter I was amazed at how loosely it fits. Even with the retaining bolt in position the filter can still wobble around, and seems to be kept in position partly by the sump once that is in place. Should it be like this, or should there perhaps be a spacer on the retaining bolt so that the filter is kept securely in place? I am not convinced that it is an airtight fit. Should I drop the sump again to secure the filter in place, and make sure that the pick-up tube is secure? Kind regards KC | ||
| David Gore Moderator Username: david_gore Post Number: 1000 Registered: 4-2003 |
Hi KC, It is completely normal for the filter to be a loose fit in the sump. I f my memory is correct, Bill Coburn wrote an article in "Tee One Topics" on replacing the pick-up tube O-ring. The O-ring is located on the top of the tube where it goes into the valve body and this is the reason it can be overlooked during reassembly. If I were you, I would drop the sump pan and check the pick-up tube before contemplating removing the transmission. There is a good possibility the missing O-ring could be the reason for your problem. While you have the sump out, I would also purchase a drain plug adapter kit for the T400 and fit this to make future transmission oil changes easier. Hope this helps. Regards David | ||
| KC Saayman Prolific User Username: kc_saayman Post Number: 108 Registered: 10-2004 |
Thanks David. I did replace the o-ring, but nevertheless I think I will drop the sump again to make sure that the pick-up pipe is secure. The whole assembly just seemed very wobbly to me. Can anyone perhaps point me to the specific T-One issue that featured the article about this? (In the meantime I am doing the final assembly after replacing the exhaust valves on my Bentley S1. Wow, what a job! But most enjoyable and I have learned so much during this project! So the Shadow gearbox giving trouble now comes at a bad time because the Bentley is taking up so much of my time) Regards KC (Message edited by KC Saayman on 26 April 2011) | ||
| David Gore Moderator Username: david_gore Post Number: 1001 Registered: 4-2003 |
Hi KC, Have a look at the following links: http://www.rrbew.co.uk/Pdfs/T026.pdf Go to page 370 for a photo of the pick-up tube and O-ring. http://www.rrbew.co.uk/Pdfs/T02.pdf Go to pages 7 and 8 for information on changing the T400 oil and filter. http://www.rrbew.co.uk/Pdfs/T043.pdf Go to page 636+ for a comprehensive overview on the T400 - this also includes a reference to the loose filter being standard. | ||
| Neville Davies Experienced User Username: nev_davies Post Number: 23 Registered: 9-2006 |
David KC If the fault arose before KC opened up the box it would seem that the filter having worked for this long was OK.How about towing the car up the slope and onto the road (engine running of course) and driving the car forwards if all 3 gears are OK then the rear brake band or servo would be suspect.If 3rd gear slipped the the clutch would appear to be the culprit.The rear brake band servo may be repairable in place.The clutch will need the box removed. Nev | ||
| David Gore Moderator Username: david_gore Post Number: 1002 Registered: 4-2003 |
Hi Neville, If the oil pickup O-ring is OK, my money is on a worn-out clutch pack. The amount of built-in slip to give a "silky smooth" gear change significantly reduces the life of the clutch plates. This was a marketing ploy by R-R/B for the US market [along with the soft suspension] as this was their key target for the Silver Shadow. A boulevarde ride was seen as the most important selling point to US luxury car buyers to better the Lincoln and Cadillac alternatives. | ||
| KC Saayman Prolific User Username: kc_saayman Post Number: 109 Registered: 10-2004 |
Hi Neville The car performs perfectly in the forward gears. Is what you suggest a DIY job, or best left to the professionals? I have dropped the sump again and replaced the o-ring again. That all seems fine now. What did surprise me is that I cannot get more than about 5 liters of oil into the box without it indicating on the dipstick that it is full. I forced about 8 liters into it and now it indicates well over-full, even after running it and shifting trough all the gears etc, as per the book. According to the information I have the gearbox takes 10.6 liters of oil. When I engage reverse I get the usual slight motion, and the car inches back momentarily with the handbrake off, but there is still no drive. I am beginning to think that I have done what I can to rule out anything minor, and that the box will probably have to be looked at by the professionals. Sigh. Regards KC | ||
| David Gore Moderator Username: david_gore Post Number: 1005 Registered: 4-2003 |
Hi KC, When you change the oil, the oil in the torque convertor does not drain out with the oil from the sump. This is why it only took 5 litres of oil. Flushing the torque convertor requires removal of the torque convertor and flushing on a bench rig by an experienced transmission service specialist. You can do a partial flush by draining and replacing the fluid; driving the car then draining the transmission and refilling with fluid however this will not completely remove any clutch plate residues that might be present. My suggestion is to purchase an overhaul kit and do the transmission in its entirety rather than trying to get by on a partial repair. The cost will not be significantly greater and you will have peace of mind knowing the transmission will be good for another 100,000 miles or more depending on your driving conditions - stop/start city driving significantly reduces the transmission life due to the in-built clutch slip. From your previous posts, I suspect you are capable of doing the overhaul however time and facilities may mean the job has to be contracted out to an older repairer who worked on the Hydramatic and T400 auto transmissions in the 1970's. It is an easy transmission to overhaul; the most difficult part is removing and replacing the transmission on the vehicle. (Message edited by david_gore on 03 May 2011) | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2309 Registered: 4-2003 |
Just a few follow-ups on David’s notes. You can flush the converter in-situ but it is very wasteful of transmission fluid. Usually it is done by disconnecting the fluid cooler feed and purging fluid through the opening. All the fluid goes through the converter before going to the cooler feed line and hence flushes the converter. By the way, overfilling the transmission can damage it badly. The other way is to drill a hole in the converter, then pop-rivet it back together afterwards. See the picture below from Ron Session’s book, but I wouldn’t consider it personally. I would do neither as in reality the fluid lasts the life of the transmission, and changes are only really nice to have. Important is only to replace the filter. Concerning overhauls, I too am quite capable of overhauling a THM400 but have never bothered (earlier 4-speed Hydramatics are a different matter and best overhauled yourself). As soon as there is a leak in the front or any internal defect I simply book it for a full overhaul as overhauls cost very little done professionally as the THM400/3L80 is so ubiquitous. To R/R the transmission is half the work, so anything less than a full overhaul is throwing good money after bad in my book. Also, you will have 1-3 years’ warranty on a full overhaul or none on a partial overhaul. RT.  | ||
| KC Saayman Prolific User Username: kc_saayman Post Number: 110 Registered: 10-2004 |
Thank you very much for all the responses. I have learned a great deal from this discussion. Much appreciated! I will have the gearbox overhauled by the professionals. That sounds like the best way forward (or rearwards in this case!) Kind regards KC | ||
| Neville Davies Experienced User Username: nev_davies Post Number: 24 Registered: 9-2006 |
KC As Richard and David have suggested if you have to remove the box then only a full rebuild is practical including re-con convertor and a cooler flush.However it is possible that the rear servo seal has failed if this is the case and the brake band is still intact then renewing it in place is not difficult.The proceedure will be in the tech library and is quite straightforward could save you removing the box and is worth a look Regards Nev | ||
| David Gore Moderator Username: david_gore Post Number: 1006 Registered: 4-2003 |
"Just a few follow-ups on David's notes. You can flush the converter in-situ but it is very wasteful of transmission fluid. Usually it is done by disconnecting the fluid cooler feed and purging fluid through the opening. All the fluid goes through the converter before going to the cooler feed line and hence flushes the converter." Richard, Thank you for this tip - never thought of this technique and neither did Ron Sessions!! As you say, it would use a lot of fluid and also be rather messy. If there has been a major clutch failure with lining residues evident throughout the transmission, the torque convertor must be flushed to avoid recontaminating the transmission after overhaul. This was the case with DRH14434 when the clutch pack disintegrated after the flexible hose to the oil cooler burst and dumped all the fluid whilst the car was climbing a rather steep hill. I overhauled the transmission myself but had the torque convertor flushed by a drag racing transmission specialist who had a rig to do this. | ||
| KC Saayman Prolific User Username: kc_saayman Post Number: 111 Registered: 10-2004 |
“KC As Richard and David have suggested if you have to remove the box then only a full rebuild is practical including re-con convertor and a cooler flush.However it is possible that the rear servo seal has failed if this is the case and the brake band is still intact then renewing it in place is not difficult.The proceedure will be in the tech library and is quite straightforward could save you removing the box and is worth a look Regards Nev” I am very interested to read more about this, but cannot find the link to the technical library. Is it somewhere on the Forum Home Page? Regards KC | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2310 Registered: 4-2003 |
http://www.rrtechnical.info/ It is also accessible via the RROC(A) home page. |
