I know there has been threads regarding the lsd and rear end swaps so I will keep this simple. I searched the archives, faq and current threads for the past 1 1/2 hours and have somewhat of an idea on what to do. I swapped the pumpkin from my 84 se in to my 84 gs and kept the same axles for the bolt pattern. I know of the disc and susp. upgrades but am not concerned of this. I took the rex out and put 125 miles on her before I heard the thumping in the rear end. I have an 83 gsl out back and need to know if I am right on this. I will need to change the driveshaft ( or flange on the pumpkin ) and switch the complete housing and all due to the difference in axle size correct ? Which also means I will need the brake lines as well. Or should I find ( where ) the parts to rebuild the lsd pumpkin from the se. Gear ratio difference is very minimal so not too concerned about that. I ask this cuz I have put about $2500.00 into her this last month and really can not afford a whole lot more, however I want to drive her sooooo bad. Also, in Michigan the 7 is increasingly difficult to locate parts, new or used. Thanks in advance guys, any advice would be very helpful.
Jim

 

bump

 

If you switch to the 83 rear end, use all of it. It may or may not have the large pinion flange. If you have the 83 driveshaft, don't worry about it, use that one. If you don't have the 83 shaft and the do have the small pinion flange, change in the larger one to match the S3 driveshaft.

Brake lines will mount up woth no moddifications at all.

You might want to explain the noise you heard a little better before you start switching rear ends. Depending on what it is, the switch may not be needed.

 

The noise is a real low thud thud. It is steady and coincides with the revs of the drivetrain at a coast or with the clutch pushed in. When it is under load such as braking or acceleration it disappears. It started out really low and had become progresively louder as I drove it home. About 15 -20 miles. If I remember right last year it made the same noise and I was not careful with it and next thing I knew I had busted the teeth on the other dif. I almost think it may just be bearing noise but if neglected it will become a complete rebuild. I do not know how long the SE sat before I bought it and then it sat another year or two and my thinking is that maybe the bearing was bad but had enough gunk to keep it good for the first 125 miles. Once the new fluid ( amsoil ) worked through and cleaned it out it showed up. I am pretty sure it is not lsd chatter since amsoil has the additive in it.

 

You may be right, but start with the driveshaft and u-joints first, just in case. If those are good, have fun changing the rear end out.

 

Driveshaft does not have interchangeable u-joints correct. At least I know I read that somewhere in the mazda books. Maybe it was for earlier versions. If it was a u-joint I would feel a vibration either on take-off (rear) or slow down(front) and I am not, it is very smooth.

 

One more tidbit. I called a garage this morning that specializes in difs and they said they would have to split it to determine if it was a bearing. Cost about 150 -185 for a total rebuild. I also have an in at the Mazda dealer so I can get parts for cost and they( garage ) were willing to give me a list of what would be needed. If it is only a bearing, I should not have to replace the ring and pinion or the spider gears right ?

 

where in michigan are you located? I highly doubt that a bearing would go seemingly instantly from quiet to a thud-thud-thud. I think my bearings are starting to go in my rear end, i have an '82 GS, and i have a thrumming noise coming from my rear end. Sounds like a worn out bearing to me. I agree with trochoid that it could be your driveshaft. Before you go about ripping out driveshafts and your rear end, have you checked your tires? If you slipped or broke a belt while driving, it makes that kind of noise and will get progressively worse. Swap your rear tires to the front and front to the rears and see if that helps out at all.

 

If it is only the wheel bearings, the rest may be good. If one bearing needs replacement, do both, it's cheaper in the long run.

Edit.

Now that I think about it, I remember in high school a friend of mine kept blowing the r&p on his 59 Impala. Missing one tooth makes a definite thud-thud. Just hope for the best.

A good driveline shop can remove the u-joints and replace them with replaceable and greasable joints.

 

located in Holland area on west coast. If it were the tires I would hear it wether or not there was pressure on the rear end. This noise only occurs during a coast or acceleration, but thanks for your input. I will be putting the driveshaft from the SE in to see if that makes a difference. As I mentioned earlier though, I had the same noise last year before my other dif went out. Started out really low thud thud and progressed. I continued to drive it for another week or so, aggressiviely at times and then it completely went out. Pulled it and had several teeth broken.

 

That makes sense, considering the history I have had with the rear end in my 7 and the noise it could easily be one tooth. However we checked it over real close before we put it in and all the teeth were fine. Unless it is one of the spider gears which you really can't see without splitting it. Everything was really tight. I didn't think tooth would break within 125 miles if the clearances were fine. I did not drive aggressive at all. Still had another 200 miles before the clutch was broke in. We will know soon enough, I will be pulling it in the morning and let you know. By the way, checked out the pics of your widebody, very nice. Not criticizing but it seems from the pics the ride height is up there a little. Is that purposely done ?

 

Holland eh? I'll be putting together the Grand Rapids meet again in a month or two. Hope to see you there. Check 6-mile autoparts (just North of GR) for parts, they have a few 7s up there and pretty good prices.

 

No the height is the standard Eibach lowering springs. The Epsilons wheels and 15" tires do raise it a bit, probably near stock height, but it can't go much lower than it is now because of the front air dam. I tore that up the first time I pulled in the driveway. The fenders also give the illusion of more height.

Thanks for the compliment.

Spiders usually clunk more on turns. When going in a straight line, they are all turning at the same rate.

 

our giving away a source for parts...lol. Thanks for the info, that's what this forum is all about. We all share the love for the 7. I will surely be there, just pm me when it gets close with the details. I will be in GR tomorrow dropping my dif at D & R driveline ( Jenison ), ever heard of them ? Maybe I will check out 6 mile autoparts while I am there.

 

I wasn't sure how that worked (spider gears ) since this is my first lsd. I know the noise in my last dif stayed the same as this noise for about a week, then it developed huge miss in gear and it turned out to be 4 broken teeth. I hope it is not the r&p. Do you know where to get them for a decent price versus mazdatrix and racing beat. Last checked they were around 350.00. I am going to put the other driveshaft on today and check it before I pull the pumpkin.

 

I am a big giant dumbass!!!!!!!!! I figured out the noise in my rear end after I changed the driveshaft, took it for a ride and still heard it, put it up on jackstands, still heard it but only from the driver side, grabbed the lugwrench to pull the wheel and noticed 3 of the 4 lugs loose. Tightened em down and low and behold, the noise disappeared. If you could seem the shame on my face you all would be laughing. At least I know I have 2 ggod driveshafts now ...lol

 

Don't feel bad, I should have thought of that too. Good thing you caught it before the wheel exited stage left.

 

Good thing since I was up at 110 mph down the stretch of road by my house when the noise showed up. I have a nice section of road that is dead straight for about 2 1/2 miles in the country, perfect for getting the 7 up to speed. Got on it a little harder today and wow do I love the lsd. Also did the mechanical secondary trick but not too sure how I like it. Definetely quicker in the mid rpms though, just have to get used to a little lighter pressure pedal. Put another 100 miles on it today. A few donuts in the parking lots and some intersections. Why would anyone want to drive anything else. Tomorrow I will really be getting on it to test the handling and takeoff, clutch is pretty much broke in now.

 

Wait until it rains and the streets are a little wet/damp. Lsds are sooooo much fun then. I find it quite easy getting sideways by hitting 2nd gear a little harder than normal driving, even with the big *** tires.

 

That was the case yesterday...rained a little in the afternoon and wet the pavement nice. Every stop and go and turn was a blast. And with the new centerforce clutch she grabs hard in 3rd, even got a little sideways once. Today sucks though, forecast for rain most of the day and then possible snow. UGH....some times I really don't llike Michigan. By the way, I really would like to thank you for the all your insight and help the past couple of days, much appreciated.

 

Most welcome. Just be careful enjoying the clutch and lsd, don't need new pics in the wercked 1st gen thread.

 

for sure. My baby is in too good a shape to be wrapping around any trees and such. I have been all through it and found on quarter sized rust area on the storage bin on the drivers side. Other than that it is solid with no rust. Amazing for a Michigan car but she has never seen a winter. Hell, I won't even put it on the road until all the salt has been washed off. Undercoating is still on the underside as well.

 

Glad you figured it out man. Also nice to hear that not all of the 7s in Michigan are rotting out. Take good care of it!

 

You will see her soon enough, whenever the meet is gonna be. We should try to get together one day on a weekend. I am in GR usually once a week. In fact, I may be taking the 7 up there for a cruise this evening. She hasn't tasted the open highway for more that 12 miles in the last 8 months. I would like to see your baby as well.