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Vladimir Ivanovich Kirillov
Grand Master
Username: soviet

Post Number: 982
Registered: 2-2013
Posted on Tuesday, 26 June, 2018 - 08:28 am:   Edit PostDelete PostView Post/Check IP

This is a question that has gnawed on me for years.

GM made a ton of these things for various models.

RR used it. Question do any of the internals from the US cars is Cadillac, Buick, Pontiac fit in the GM four speed of RR/B?

Richard Treacy must know the answer.
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David Balfour
Frequent User
Username: sidchrome

Post Number: 99
Registered: 2-2009
Posted on Tuesday, 26 June, 2018 - 09:58 am:   Edit PostDelete PostView Post/Check IP

Yes, all of the major mechanical internal components are identical except the output shaft and body, and torus cover. However, Rolls-Royce made some subtle changes to valving spring rates and adjustments in order to tailor shift characteristics to meet Rolls-Royce requirements. The RR boxes were assembled by RR not GM. I have been told that RR used a slightly different clutch plate in the clutch packs, although I am not entirely confident that this is 100% accurate. Richard may know this part. Over time GM made changes to the components of the gearbox, probably including clutch packs. It was used in non-automotive GM applications as well (think tank transmission - 1 per side) l and the changes may just well reflect later evolutionary improvements. I think RR used this design well after GM had moved to newer designs like the Powerglide. What I can say is the output stages and the torus cover are unique to RR cars as ours have the mechanical servo. Unlike the pronunciation in "Grease", Grease may be the word, but the gearbox is a Hydramatic not a Hydromatic. Also, it is actually a dual range 2 speed automatic box, unlike the turbo-hydramatic which followed in the Shadows which was a genuine 3 speed. So first is Low 1, second low 2, third High 1 and fourth high 2. That makes the 2-3 shifts slower than the 1-2 or 3-4 because it has to change both range and ratio in a 2-3 shift. If you are buying an overhaul kit there are 1 or 2 critical gaskets or seals that are not found in the Fatsco version of the RR hydramatic kit, that need to be sourced independently, so I recall. Feel free to correct any technical errors I have made.
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David Gore
Moderator
Username: david_gore

Post Number: 2940
Registered: 4-2003
Posted on Tuesday, 26 June, 2018 - 10:03 am:   Edit PostDelete PostView Post/Check IP

Vladimir,

I cannot help with the Hydramatic however based on my knowledge of the later T400 3 speed transmission, I suspect it would have been a Cadillac version and most likely unchanged as it was early days for auto transmissions and the US lead the world at the time.

The T400 was a Cadillac version with some very minor R-R tweaks. I rebuilt the DRH14434 transmission using a standard B&M T400 transmission overhaul kit and the only additional part I had to purchase was a "wave" first clutch plate to replace the flat plate in the transmission kit.

I did make the B&M suggested street and strip modification to the valve body to reduce clutch plate slip during gear changes. The R-R units are set up for imperceptible gear changes for normal driving however, they are prone to excessive clutch and friction plate wear in cars predominately driven in stop-start city traffic. The changes are firmer and slightly more noticeable in normal driving and come into play when driving enthusiastically [standard for me!!!!!!].

The rest of the transmission is standard GM Cadillac components if my memory is correct.

.
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Jonas TRACHSEL
Prolific User
Username: jonas_trachsel

Post Number: 179
Registered: 2-2005
Posted on Sunday, 01 July, 2018 - 04:27 am:   Edit PostDelete PostView Post/Check IP

I was told that using standard GM flat clutch plates leads to overly harsh gear changes. Get the correct vavy R-R clutch plates, they are still available from the specialists.
Another critical point to get smooth gear changes is a shift linkage without any noticeable play, as the range of correct adjustment is very narrow.
My twopence worth of inf. JoT
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David Balfour
Frequent User
Username: sidchrome

Post Number: 100
Registered: 2-2009
Posted on Sunday, 01 July, 2018 - 05:45 am:   Edit PostDelete PostView Post/Check IP

i was told the same thing about using the wavy plates in the clutch packs as Jonas. It's really hard to tell fact from fiction when it comes to the 4 speed Hydramatic. Wavy plates, flat plates, softer springs, firmer springs? My transmission was rebuilt using the flat plates. Shifts feel just as smooth as any other Silver Cloud I have driven or ridden in. Another friend also used the same plates that come in the Fatsco rebuild kit. Guess what, same smooth result! Anyone noticed harsh gear changes in a restored Cadillac? Bad adjustment can certainly lead to harsh gear changes. I heard the story about the wavy plates long before I rebuilt, but could not justify paying the prices for RR sourced parts for a US sourced gearbox, when US restorers and US gearbox specialists are using US kits with fine results. Do you really think a Hydramatic Specialist in the US sends to the UK for wavy plates when he builds a Rolls-Royce 4 speed hydramatic box? Perhaps the key is ensuring that all the overhaul parts are matched to each other and that the adjustments are correct. I suspect proper adjustment is the key to many issues. Speaking of adjustment, I also have some doubt about the accuracy of the Rolls-Royce transmission setting tools found in most export cars. The springs on these things are kept under compression their entire lives. Weather based thermal cycling means they likely stress relieve in time and lose some of their rate. They are set to spec by length adjustment, not force, but are required to deliver a specific force. I know someone measured one and found at the set length the force was nowhere near high enough. I think I saw a recommendation from a RR mechanic to use the tool with a different number of turns from the manual. Maybe to compensate for the setting spring. At least he can get consistent results with the tool.
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David Gore
Moderator
Username: david_gore

Post Number: 2956
Registered: 4-2003
Posted on Sunday, 01 July, 2018 - 10:43 am:   Edit PostDelete PostView Post/Check IP

I purchased my "wavy" clutch plate from a transmission parts supplier with no mention of it being for a "R-R" transmission to avoid being charged "R-R' prices.The counter salesperson bought out a box of loose plates with a printed GM part number and product description on the outside.

Fitting the "wavy" plate to the Turbo 400 was overkill on my part and insurance against possible clutch problems if I installed the flat plate supplied with the overhaul kit. I also made the "strip and street" valve body modifications suggested by B & M to reduce the inbuilt "smooth change" clutch slip in the interest of improving future clutch life.

A recognised R-R repairer once told me the typical life of the T400 clutch plates was about 100,000Km in predominantly stop-start city traffic driving.
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David Balfour
Prolific User
Username: sidchrome

Post Number: 101
Registered: 2-2009
Posted on Sunday, 01 July, 2018 - 05:48 pm:   Edit PostDelete PostView Post/Check IP

It's worth remembering that the 3 speed Turbo Hydramatic 400 (THM400) and the 4 speed Hydramatic are entirely different gearboxes. Still it's interesting that there is a clutch pack option. I still wonder if one style of plate is a "later" development?
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David Gore
Moderator
Username: david_gore

Post Number: 2957
Registered: 4-2003
Posted on Sunday, 01 July, 2018 - 05:57 pm:   Edit PostDelete PostView Post/Check IP

I know....... however the "wave clutch plate" is common to both R-R/B versions of the Hydramatic and T400 auto transmissions hence my contribution.
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christopher carnley
Unregistered guest
Posted From: 109.149.198.181
Posted on Sunday, 01 July, 2018 - 06:59 pm:   Edit PostDelete PostView Post/Check IP

We in the UK buy parts from "Fatsco" in the USA.
They are the only genuine supplier of the wavy clutch plates variant for Rolls-Royce.They also have all the other GM pattern parts.
See ebay.com. Motors.
As with the old R-R Heavy clutch, the "wavies" give progressive engagement.
The flat GM plates are 1-2 thump!

(Message approved by david_gore)
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Mick hall
Unregistered guest
Posted From: 77.96.150.90
Posted on Tuesday, 17 July, 2018 - 04:44 am:   Edit PostDelete PostView Post/Check IP

Re wave or flat clutch plates in four speed cloud g/box,if you want good changes Donít buy.the mega expensive red faced flat plates from rr they result in bad changes,the fatsco plates are ok & there is a Mercedes benzeplatethat does the job,also Iím not a great fan of the drum seals that donít have the brass expanders,they donít air up sometimes when you check them.

(Message approved by david_gore)

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