Aloha and Happy Memorial Day! I've lost count the number of times I've assembled and disassembled this diff. What a project. Glad I'm not paying someone else to figure this out. Anyway, Here's where we are today: Orignal installed shims were: 2.7mm left and 1.7mm right. - (perfect preload but gears bind) Current installed shims are: 3.2mm left and 2.2mm right Current backlash is .003" or .07mm The crown gear and side covers are completely torqued to spec. Keep in mind that these are used gears and the pinion was never removed. I can't seem to get that pattern in the center of the tooth. It's too close to toe on the drive side and too close to heel on the coast side. However, it's feels good and "sounds" good. Here's the paint: Image Unavailable, Please Login Image Unavailable, Please Login
I misspoke about the preload figures so just disregard that 38 to 40 lbs number. Using a hand scale tied to the flange bolts and no crown gear installed, the number on the hand scale should read between 9 & 10 lbs before the diff rotates. I've confirmed this repeatedly through testing and others who have done it. However, your math appears incorrect. 7.38 lbs = 1 Nm
this sounds now much better even it is les then the WSM says, but my experience says it is nearly ok. a little bit more would be better sure??? I have written 8,8508 in.lbs ( poundforce inch ) is 1 Nm, and when I look in my conversion table it says that those 7,38 lbs ft ( poundforce feet ) are 1 Nm question now is: you meassured in in.lbs or lbs.ft? but as I mentioned before, only lbs is no torque only weight, but we talk here from torque. so I hate those conversions you can make so many mistakes when I see this pattern I must say it is not correct and I would not leave it like that. but your decision
this is what Steve Magnusson posted when I asked about torque conversions from the WSM: It's probably 5.5 daNm = 55 Nm = 40.6 ft-lb (but always match up the thread size too, if possible -- is the thread size in this particular case M10 x 1.25P?) Nm = Newton-meter (1 Nm = .738 ft-lb) daNm = deka Newton-meter (1 daNm = 7.38 ft-lb) Kgm = Kilogram-meter (1 Kgm = 7.233 ft-lb) Unfortunately, in section M of the TR WSM there is a misprint in the table heading -- where it says "Kpm", it should be "Kgm". Also, although not exactly right, they often assume 1 daNm = 1 Kgm (so they give the same numerical value for either unit). ------------------------------------------------- I've already added another .13mm shim and it brought the pattern a little closer to the center and the backlash is now at .005". I think I'm going to add one more .13mm shim and see if it brings everything in line without putting the backlash over the top. Tomorrow. It's dark now and I'm hungry!
HELP PLEASE! What's wrong here? I've now added .9mm to the original shims just to get the pattern to come close to the center. It's still not there but seems really close now. The problem is, with that much shim I've got .25mm backlash. That's out of spec. The acceptable range .12 to .17mm I didn't expect this much brain damage. Image Unavailable, Please Login Image Unavailable, Please Login
Scott, have a look at the pattern all the way around the ring gear to see if you have any variance in the pattern. If you do then the crown may be warped- fairly common. If it is straight the backlash figures given are for new and I beleive that the wear tolerance of .12mm may be added as your ring gear and pinion are used. Robs description re the turning force required is on the money. The diff feels quite stiff when cold.
If you dig deep you will find a report on my crownwheel which was certainly warped. Another done in Melbourne the same week as mine was also warped. Both were flat faced on a sheet of glass with dramatic improvement. Mine was tight in areas and loose in others and did my head in until I found that it was the warped crownwheel.
Thanks guys but I already did the staight edge and feeler guage while the crown was removed. It was flat as flat gets. I think ill have to get into that .12mm runnout but im terrified of clunking from too much backlash. In fact im almost at max runnout now at .25mm. How does thats last swipe pattern look? Drive side looks pretty close doesnt it?
If you measure a wavy washer the same way, some of the measurements would make it appear to be a flat washer. The sheet of glass is a good idea. That's why you bought that glass top coffee table... right? Rgds, Vincenzo
Read, read, ask questions, and read some more. When reading Ringandpinion.com I found this statement that seems to make a lot of sense and should help me not be so anal about perfect centering between heel and toe and just worry about centering between face and root. -------------------------------------------------- Randy Sez Reading Gear Patterns on New Gears The only part of the pattern that helps me set pinion depth correctly is the contact position between the face and flank. If the pattern appears to be toward the heel or toe, I pay little or no attention. While making adjustments, the pattern may also change toward the heel or toe, but in most cases this aspect of the pattern cannot be put into an ideal position. Even if it doesn't seem intuitive or reasonable, I am only concerned with the pattern position between the face and flank. I have found that housing alignment and the exact position of the pinion bore during manufacture affects the heel to toe pattern and cannot be altered without machine work. Bottom line: a contact pattern that is centered from face to flank always indicates a correct pinion depth, even if a centered heel-to-toe pattern cannot be obtained. ----------------------------------------------------------------------------------- Anybody got a problem with this?
Uh, only if you check it in 2 places. I ran that straight edge in at least 10 different spots and never found any clearance. She's as FLAT as my first girlfriend!
a bit off topic...but...if you bought the newman parts....could you do this in car? Is there a good DIY article? If you kept your bearings, shims and all other parts, would the problems in this post still exist? I would love to see a good DIY tech article to prevent failure.
First of all I believe Newmans and Forza's diffs are virtually identical although reading through this forum, you will hear them argue with each other about who's is better. Just a pissing match as far as I'm concerned. They are both beautiful. I bought Forza's because it was overall a bit cheaper and for some other personal reasons I won't go into here. Can it be done in the car? Yes, but you're a glutton for punishment doing it that way and the likelihood of doing it wrong seems much higher. I think the amount of time required to remove the engine is equivalent to the extra work required to do it in the car. And it won't hurt as much. I used my original crown and pinion gear. The only thing new was the left side cover, the diff, the bearings, and 1 race (cup). Due to the very very small tolerances in backlash (you're only allowed to be from .005 to .007 inches) I have currently spent many many hours assembling, disassembling, measuring, changing shim sizes and doing it all over again and again. If I did this in the car I would be cripple. With that being said, there are some who claim they have swapped the carrier and used the exact same shims. Most of the experts here say they were either very very lucky or they were wrong. Considering the cost of these parts, I don't want to be wrong. Keep in mind that my carrier exploded. Therefore I had to change the carrier and the left side cover. Currently, I have added .5mm to my original shims to obtain the correct backlash. That's .019". In comparison to the tolerances, that's a huge number but still very very small. Simply by adding .13mm shim (.005") decreases backlash to 0. So you can see how fine these measurements are. The likelihood of using all your old parts and having it line up is slim especially if you've had the failure. Maybe replacing it before the failure would help but you better measure, disassemble, reassemble, measure again, and then ask someone else if it's right. JMO - FWIW
Where the heck is everybody? (No offense to those who've posted) Well, considering I can't get the answers here after waiting for days, I have setup this diff the way I think it feels and looks best, painted it in 4 locations, removed it, and I'm going to take it to my local diff guy who gave me the shims. I'll let him tell me if I'm right or wrong. I posted a statement from ringandpinion.com above. If that statement holds true with what I'm doing here, then I've got it dialed in. The pattern is toe in on the drive side and heel out on the coast side but it appears to be centered between face and root. I've got .005" backlash which I think is great under the circumstances. I don't want the max backlash because I'm afraid of clunking after it warms up so having it on the minimum I think is good. Kerrywittig expressed the same dissatisfaction about input from the experts here. I read his thread and couldn't see where anyone answered him either. Hey Phil Worral! It sure would be nice to have a bit more support considering I bought this from you! Not saying that you didn't give me the right info but it seems you disappeared as soon as I started having trouble. In the end I don't think my problems have anything to do with your part but the support sure would be nice considering the $3000 price tag.
I feel like I'm talking to myself at this point but... Here's some nice up close pics of the final swipe. This is what I'm taking to my diff guy for his opinion and most likely what I'm going with. I know drive side is still on the toe and coast is still on the heel but I can't do anything about that. It looks centered otherwise and the backlash is .005". Image Unavailable, Please Login Image Unavailable, Please Login
Robert, In the end it appears that you were dead on. We had almost identical shims stock. I was at 2.7mm and 1.7mm You added .8mm and I added .6mm. I think you're probably right about the Capristo carrier cutting the bearing hole too deep. I would have to say your input and experience are invaluable. Had I not known that you had the same experience, I would still be scratching my head wondering what I'm doing wrong. Hopefully this thread will be useful to others who are trying to install a new diff and new side cover while retaining the original C&P. I'll let you know tomorrow what my local diff guy says about that pattern and ultimately I'll let you know how the car drives. Keep in mind, my diff guy agrees with the statement made on ringandpinion.com. It isn't as important to center the pattern between heel and toe as it is to center it between face and root. All I can say to others in this situation is, if you don't understand, read read read. Look at picture examples, watch videos of the process, ask questions and then do it yourself over and over. Once you understand, it is quite simple. Aloha & Mahalo
hey scott, as I see it you have got from phil worral some parts you need to rebuilt your diff? if you now think you can do your diff as good as a specialist and then later ask here about how to do it and also write here that you expect more support from phil I would say that this is not fair. those diff parts are very rare and not so easy to get ( good ones ). so you may be proud that you got those parts. some here gave you good ideas how to do it. also I put in here 2 pictures how it has to look perfectly ( post no. 18 ) . you can not take the data to be used from other who did the diff once. the housings are not all equal and so it has to be meassured all several times before it is perfect. even from factory it was not always perfect. so I repeat what I think to your diff adjustment: the pinion seems to be to much backwords. you see this on the color where the pinion touches the crown. too much to the center of the diff. I meanwhile have done 3 complete gearboxes ( all are running fine ) and it took me always a lot of time to adjust first of all the diff. but I never wrote down the sizes of the shims I needed because this always varies from gearbox to gearbox. so I can not say what shimsizes I put in on what side. I wish you continued success in assembling
Yes Romano, I support you (and Phil). Plus: Phil is no mechanic ... he just made it possible to fabricate these perfect diffs... And maybe he is not at home or even in the U.K. in this moment ... The $ 3000 is a bargain, you should be grateful ... do you know the Ferrari oem pric of a diff ? More than twice this price ... And NOT a life-time guarantee . So in stress, don't be not-nice to other people; the rest here will help you as much as they can. I also have such an U.K. diff and had Cavallino install it; I also am not a mechanic. But I am still very greatful that Phil supplied me with this diff .....
Ok, maybe it came across a little harsh on Phil. That was unintentional. As I said, in the end he gave me good info. It just seems that someone who made so many of these diffs would be a bit more knowledgable about this problem. Knowing now that he is not a mechanic, I understand why he referred me to Robert Hayden. So Phil if you read this, Sorry I wasn't trying to be mean. Romano, if you read everything I posted in this thread you would know that Robert has also installed 3 of these diffs. Fortunately for me he used a Capristo side cover on his own car and was able to show me that the bearing hole is cut too deep. That appears to be where my problem came in. I know that everyone says shimming is never going to be the same when you replace parts. However, all things being equal, the difference between original shims and where you end up after replacing the diff should be within maybe .003" to .006" as long as there is no other damage such as the case stretching. When I have to add .023" it raises a red flag for me and I start looking for other problems and found it in the Capristo side cover. (Thanks to Robert for pointing me there.) Also Romano, I know you think my pattern is not good but I have read numerous places and talked to numerous diff experts who have told me the same thing - It is not as important to line up heel to toe as it is face to flank (root) and installing used gears, I am much more likely to have this kind of pattern. There are numerous comprehensive diff setup websites out there that show my type of pattern as acceptable. Mel, Romano, Phil, Robert, Steve, and others have all been a wealth of information and I would never have attempted this without the support of you guys and this site. I haven't turned a wrench professionally since 1990 but I was factory trained line mechanic for GM, Nissan, and Jeep. Most of what I know has come from experience. I've installed a lot of diffs but they have always been pre-assembled. This is only the second diff I've ever setup and the first was done over 25 years ago for a 1 ton truck. Once again, please don't take my frustration as an insult. I am very grateful.
sure scott it is acceptable as you did it now, but not perfect. also I understand that after soooo much work it is frustrating not to get it really right. I never tested an original diff how this will be moved in and how the pattern would be on such part. I´m sure it is also not perfect. but for me it is always important to do work as good as I can and as good as it is possible. that is why I don´t want to have this acceptable pattern you have just now. because if this pattern is not ok the load for the left side cover is also different than expected. that may be also a reason the original ones sometimes break??? those 3 gearboxes I already did have until now no problems with broken covers or some noises. and I hope it will stay this way
Try get in cpontact (PM) with my mechanic, who installed my U.K. diff; he lives in Germany ... named: cavallino70 He recently posted in the carcover thread ... He has done over 100 of these gb's !!! For me he is THE EXPERT here ... he only goes for the perfect fit; like country-man Romano ... (both Gemans) Good Luck !
Scott I have been away on holiday in Dubai for a while. I am back now so if there is any more help that you need feel free to ask. I see that you, like Robert, found that the replacement diff side cover is too deep, that I why I put you on to Robert as he has first had knowledge of what you can and cant do with the new cover. Also Robert has had a catastrophic diff failure and documented a "bent" crown wheel, his advice is helpful here as well. Anything else please feel free to shout out. Phil
Aloha Phil, I figured you were probably away. Dubai of all places! You really get around. If there's one thing I'm learning through all this Phil it's that this is a very complicated yet simple. It's simple to understand but complicated to get it right. For those following along, here's more news. I took the painted crown gear to my diff guy and he looked at it. He said no. It's not right. (Romano just said "AH-HA!" only in the German version) He said I could probably install it and it would work but might be noisy. I won't accept that. Apparently either I've machined the cup too much or the hole in the Capristo side cover is off center. I think it's probably the cup but I have several methods to test which it is. I'll get back to you all hopefully with good news and a good pattern. Otherwise, the Capristo may have to be returned. We'll see.
Your process shouldnt be as difficult as it seems to be. 1. Fit the diff and get preload correct. This gives you a maximum shim number. Call it 3.65 for example. 2. Fit the crownwheel and make sure preload doesnt change. If it does, then crownwheel is bent and is pushing into the pinion head giving you inaccurate readings. 3. Check blueing of the teeth. 4. Remove material from LHS and fit to RHS or vice versa to move the diff left or right to get teeth position correct. Always maintain 3.65 shim material and your preload just cant change. 5. At this point you have the preload correct and you have the diff position correct as your teeth markings are right. 6. Now backlash. Pull the crownwheel into the pinion to reduce backlash, push it away from the pinion to increase backlash. Obviously this has an effect on the teeth positioning, but its negligible as we are talking miniscule changes here. If you are still having serious issues, then something is not right. It wont be the depth of the bearing as this was catered for in step 1. If you are 100% that your crownwheel is straight, then it wont be this. Personally I wouldnt trust a ruler or straight edge. I got a flat sheet of 10mm float glass about 600 x 600mm. To this I fixed three sheets of emery paper using masking tape. 1200 / 1500 / 2000 grit. Throw the crownwheel on the 1200 and use a figure 8 pattern and see what markings you get. Use wet and dry if you like, but I did mine dry. If you get a perfect polished surface, then its flat. I dont think that you will. I reckon it will either be warped or most probably show some cupping. But you need to make sure. This is critical. You will never ever get it right unless you verify this step. If the crownwheel is not 100% flat before you bolt it down, 70nm is not enough to straighten it and you will definitely get mixed messages when trying to set up your backlash. It took me 4 hours of sanding and many, many sheets of quality abrasives to get this tiny bit of cupping on my crownwheel perfectly flat as the steel is as hard as the hobs of hell, but when refitted, instantly everything fell into place. When checking your preload and back lash you need to check it at multiple rotation points. Ie: Try it, then rotate a few degrees, try it again, rotate a few degrees, rotate again until you come around full circle. If there are light spots or heavy spots then odds are you have a bent crownwheel. In a perfect world, we would like to see perfect backlash attained when the teeth meshing is also perfect. Last time I looked, we dont live in a perfect world. Your teeth mesh must be very close to perfect though, and then just move the diff VERY SLIGHTLY left or right to get your backlash correct. Shim sheet material should be available from your local bearing supplier in really thin sheets of about 9 square. These can easily be cut with quality scissors and then punch the holes on a nylon sheet. Use this micron thin shim stock to fine tune.
This bothers me a little. How did you machine the bearing cup? This has to be a tight fit, not too tight that it won't come out by dropping the housing onto a length of timber for instance, but it should be so close that even the smallest degree of tilt when installing would make the bearing cup bind in the alloy housing. Fitted in a lathe with some quality emery will take enough off to do the job, any more and you may have issues. If the centre hole in the carrier is off then you will get high and low spots on the diff itself. Set up a dial gauge and rotate the diff checking for off centre. Easy to check.
