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930 Ring and pinion, considering something "not recommended"

I'm very unhappy with the sounds coming from my A.M. Engineering (made in Italy) ring and pinion gears. It's been a long effort to straighten out the muffler, sound pad, interior sound proofing, and the speaker holes into the wheel tubs. Now that I have that noise under control the singing ring and pinion is the loudest thing in the car. It's about 10% higher ratio than stock. I don't need the additional revs as I have a pretty wide power band and first gear with my mods is essentially just for spinning the tires.

I have the original Porsche parts including bearing still pressed on the pinion and the bearing race. I found a receipt for syncro work, but nothing on the R&P at all. I suspect it was just installed without regard for shimming and that this accounts for the noise. I am sure that with the factory tool up over $2500 that having it done by someone with the tool will be expensive.

I wonder if, given the odds that nothing was changed to set the preload on the new R&P, I could simply install the original R&P and have the correct preload? Has anyone been into one who can tell me what the chances are of a correct setup?

I'm not afraid of transmission work, but I don't want to have an even larger problem on my hands here. Ideas? Suggestions?
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Andy Glass
'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 11-08-2007, 07:50 PM
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Quote:
Originally Posted by ayglass View Post

I wonder if, given the odds that nothing was changed to set the preload on the new R&P, I could simply install the original R&P and have the correct preload? Has anyone been into one who can tell me what the chances are of a correct setup?
I would say very slim chance that it would be set up correctly.

I have only done one rear end. It was a Dana 80. I regeared it and rebuilt it. I used a Dana ring and pinion and it needed a different shim stack. So the chances of getting an aftermarket ring and pinion quiet without setting it up is not likely
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Dean
911 SC turbo, 3.0L 930 motor, G50, 930 brakes, DTA EFI, 352 RWHP DynoDynamic dyno,
Old 11-09-2007, 02:48 AM
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also remember the angles are sometimes different or after market ring and pinions to make the individual teeth thicker to add strength. which results in more noise. Especially on the ones set up for drag racing. so some of your noise might be attributed to that.
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Old 11-09-2007, 03:57 AM
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BUT, if I read his question correctly, he is asking if he goes back to stock...from what is possibly a incorrectly setup aftermarket. I think its a 50/50 really depending on IF ANYthing was changed in the initial swap. You could be dead on or twice as far out.....you really don't know.

Now, a lot of trouble, but take it apart and set the old gears in place and mark the gears foot pattern front and back side and see what she comes up with. Until you do that I don't know how'd you know.
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Luke S.
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Old 11-09-2007, 08:26 AM
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Hey Lukesportsman,

That's sort of what I was getting at. I got a quote this morning of $1500 to set up the factory R&P if I bring them the transaxle out of the car. At that price I am a little tempted to put the original back in, check it by pattern and hope the guy who installed the Italian R&P just "stuck it in". Not that two wrongs make a right usually, but if he did nothing the stock one would be right.

Of course Ken911 might be right too, all the noise could be the fault of the gears and they might have been correctly set up. It sure makes a racket though.

I guess it's in poor taste to assume that the previous mechanic was an idiot, but from the noisy evidence I have so far...
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Andy Glass
'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 11-09-2007, 09:07 AM
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$1500 sounds a little rich.

Is setting up the R&P the same as setting the diff pre-load? I thought it was - and I got a complete 915 box overhaul, custom ratios, internal spray bar kit, 65/40 LSD setup and installed for the same money (although I did get some credit for the very tired mag case 915 I took in originally)...
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Old 11-09-2007, 12:31 PM
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I may have found my own answer.... I talked to an old friend today. He still works for Porsche and used to be my boss 20+ years ago. (no Geritol comments necessary)

He pointed out that since the bearing is still on the pinion, that means the pinion depth is still technically set. No one would press off the bearing to remove the shims and put it back on nice and neat. Therefore, the only thing I will have to set is lash and that's often set by feel. (if you have a calibrated wrist) Or if necessary, with a dial indicator. You could then sanity test the settings by using prussian blue to check the pattern.

I think I'm about to save $1500 ;-)
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Andy Glass
'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 11-09-2007, 06:48 PM
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Andy, are you talking about the shims under the retaining plate that holds the input and pinion shafts into the diff casing?

If so, the bearings do not have to be removed from the shafts to add or remove shims.

If you were talking about the diff I apologise.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 11-10-2007, 03:25 PM
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Hey Nathan,

I spent some time last night with the PET and the service manual. I think you are correct. The shims that set pinion depth seem to be under the retaining plate rather than under the pinion bearing. I got suspicious last night while looking at the pinion as I realized that the bearing is not a taper bearing, but a cylinder roller bearing.

My friend may have been thinking about a different transaxle (he's a shop foreman for Porsche and has better than 30 years experience). I'll have to ask him some more questions.

If I understand where those shims are (please correct me if I am wrong) they are further down the shaft from the main bearing that is next to the pinion gear.

I am also a little suspicious of the markings on the "original" ring and pinion that I have. They don't look like the ones in the shop manual. Do you recognize these markings? I would hate to put the wrong thing back into the car. I did count and it's indeed a 9/38 R&P. The teeth are lightly used and in perfect condition.


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Andy Glass
'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 11-10-2007, 04:02 PM
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The four point bearing that holds the shaft in place from moving to and away from the engine (pinion depth) sits on the shims. This bearing is then held on top of the shims by the retaining plate. This four point bearing is located on the shaft above the roller bearing if you are looking at it as if the pinion is below the roller bearing. The roller bearing takes the force side to side while the diff is getting pushed into the side cover . The four point takes care of the end to end pressure (pinion depth) as the gears are not straight cut
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg

Last edited by NathanUK; 11-10-2007 at 05:03 PM..
Old 11-10-2007, 04:57 PM
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If they are the right amount of teeth (not sure what stock was) then it should be the stock part as the date code looks about right.

My '83 3.2 carrera which is a '84MY has '83 on its 915 internals.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 11-10-2007, 05:05 PM
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Hey Nathan,

Then odds are that it's the correct one. It is the correct ratio. It simply doesn't look like the manual. Though with only a pair number (2036) and no "r" number I don't see that one can use the magic special tool to set the pinion depth anyway.

I'm also considering a test. If I were to remove the right side of the ring gear casing so that I could view the current R&P I might be able to clean it off and apply prussian blue to the installed gears. I could then print them and determine if they were shimmed accurately by mesh pattern or if they were just stuffed in there. This would only cost me a gallon of gear lube and an hour or so.

If they were just stuffed in there, the noise would be explained as a bad install and the stock gears could likely be simply plugged back in. If the pattern of the installed gears is good, but they still sound like straight-cut gears I can assume that they were installed correctly, but are of inferior quality. That would suggest that a shim adjustment would be in order to return to the factory gears as it's unlikely that both would take the same shims.

It's a puzzle that deserves at least one good beer's worth of thought...
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Andy Glass
'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 11-10-2007, 05:49 PM
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Andy, isn't there also an adjustment of moving the diff left or right? How do you know it's not been adjusted there too?

Don't want to see you damage anything.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 11-11-2007, 12:24 AM
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When ring and pinions are manufactured they are run together green (annealed) and heat treated as a pair. Each set has it's unique pre-load and they must be installed as a set.
My money is on poor installation. I'd shop around for someone to set it up properly for you.
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'91 964 Turbo
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Old 11-11-2007, 04:56 AM
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People always say the aftermarkey R&P's are not as quiet as the factory ones.
The Andial ones have been discussed on here before and were said to be noiser IIRC.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg

Last edited by NathanUK; 11-11-2007 at 12:21 PM..
Old 11-11-2007, 10:35 AM
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It looks as though there is a shim adjustment side to side as well. This is the "backlash" adjustment. From what I'm told, the pinion depth is set with the special tool based on the "r" number stamped on the end of the pinion. The backlash is set by feel or measuring the free rotation at a certain point with a dial indicator. This is something that can be set pretty easily.

Of course, without the "r" value on the head of the pinion, the whole thing is out the window anyway. You can't use the special tool without that value, so it's back to "old school" methods printing the pattern of contact between the gears and adjusting for the best pattern. I'm a little hesitant on both counts. Cash on one hand and risk on the other.
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'86 930 Kokeln IC, K27-7200, SC cams, GHL headers, Fabspeed muffler, Short R&P , misc other mistakes made...
Old 11-11-2007, 04:18 PM
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I have heard several sets of after market drag racing gears on old muscle cars and they are REALLY loud. your cheapest rout would probably be to have your set up checked for proper back lash etc. to make sure they were set up correctly. If they are set up correctly and just noisy then put the stock ones back in. Make sure you get some one good to set them up. I had the posi differential on my pick up go when it had about 160k miles on it. the guy I had replace the posi unit and gears did such a good job that it made less noise than when new from the factory. So rather than a Porsche mechanic take the diff to some good ole boy who has been specializing in rear ends for about 25 or 30 years. he can probably do a better job in his sleep than the local Porsche mechanic.
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88 turbo Guards red Targa slant nose, and yes I am a horsepower junkie, 3.4liter,7.5 to 1 JE pistons, Adjustable WUR, Imagine fuel head, 1 bar waste gate headers,allthe cis toys. Now apart to become the next EFI monster. fabbing my own intake, headers Individual throttle bodies, MS-3, pauter rods, Xtreme twin plugged heads, gt-2 evo cams cop's.
05 Cayenne S lapis blue

Last edited by Ken911; 11-11-2007 at 06:07 PM..
Old 11-11-2007, 06:01 PM
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