rear axle and gear compatibility ?

[jaywish]

Hi,

As everyone knows newer parts tend to have less mileage. Rears after 97 are not a direct bolt in.

I was thinking about getting a rear end housing 92?-97 with worn out parts, that should be easy to find.

Then getting a late model say 05-11 rear with low miles. That should be easy to get also.

Swap all newer interior components e.g. axle and gears into the 92-97 housing.

Will it all fit?

As a bonus I would have the newer vented disk setup.

Jay

[sly]

newer rear axles are longer as well... so the axles themselves will not fit in the older housings. This is as of 2003 I think.

92+ were longer than 79-91 and 2003+ are wider than all before buy another inch or so IIRC.

[jaywish]

So gears are ok but not the axles. Bummer. That would have been a big money saver.

Thanks,
Jay

[Lincolnmania]

bearing kits are cheap, unless you are planning on abs conversion i would just rebuild current rear and change the ring and pinion and add rear discs, i have been using oem used ring and pinions for years, only had one noisy set so far.

i think the reason why the new ford 8.8's have gear whine, frpp gears are made by motive gear in china now, i bet the late model oem r&p is made in china too!

[Lincolnmania]

91 boxes and some 90 boxes also have the wider rear btw.......they were gearing up for the aero so the box changed slightly in 1990.......one time at a yard i found a 3/91 box vic and a 3/91 aero vic........they must have been running two lines or they tooled up the new line fast.

[jaywish]

Good to know that some 90's -97 are the wider units. My rear whines now. I do not know about reuseing those gears with new bearings to be whine free.

I do have in mind addiing ABS eventually. I do not want to make any improvements that would have to be redone if and when I get to the abs conversion. Plus I would rather build a rear completly and then swap it in complete to cut down on down time rather than rebuilding the one in the car.

Pete/wagonman has a 96 TC going for parts. The mileage is high 300k but the car is in very nice condition for the indicated mileage. Body parts are almost all ding and rust free. Not too much rust underneath. The interior does not really look like a 300k interior either.

We opened the rear and there was a small amount of wear on the axles at the bearing location. The gears looked to be wearing very smoothly, no bad patterns. It looks like a good runner rear if your rear was shot. It is a 3.27 open. I might consider that ratio as I do not think it would hurt my fuel economy too much going from a 3.08 to 3.27. I would still have to do something about the speedo and tranny speed gears. I am leaning to hanging the late model vented disc brake system on the car. With the hope that it would better balance the brakeing performance. If it were too much I could always dial it down with the adjustable proportional valve. I would hate to convert to the early disk and still not have enough rear brake force.

I do not know how much axel wear is acceptable. You can wiggle the axels a small amount but it was not so bad that it leaked. I guess the question is whether I could just add a posi carrier and new outer bearings and be good to go. If the axles should be replaced, I would prefer to do it all at the same time. Maybe I should get a dial indicator and use that to check the wear on the gears ? I do not want rear whine when I am done with this. You can see I am concerned.

The ideal would be all new usa parts but I guess that would probably run into big bucks.

[sly]

I've had to rebuild both rear axles on the 88 and Mark. Both still have the same gears they came to me with but new bearings all around and the Mark has one new axle. The whine mine have had is the bearings or the trans.

trans whine is still there.

[jaywish]

So are you saying the bearings got rid of the whine?

How about the 93 rear, how did that turn out?

[gadget73]

They all have some in/out play. I dont know the spec offhand but there is some number. That really isn't related to the axle wear though. The bearing surface on the axle ideally needs to be perfectly smooth with no pits or grooves. Pitting is the first indicator of wear, and it goes from that to grooves to failure.

AODs whine in first and second mostly. Its a feature of the gearset. They run straight cut gears which are stronger, but noisier than helical gears like other transmissions use. If you've got whine that is vehicle speed dependent and not engine speed dependent though, that sounds like rear end noise. Usually when the gears themselves whine, its because they have some funky wear pattern or weren't set up right. Not exactly sure how you'd tell that other than trying to check the contact pattern with the paint to see how it looks. More often noises are caused by the bearings being worn out. Both the rear in my Mark VII and my Towncar whined until Scott rebuilt them with new bearings. Both have original gears but they aren't noisy.

[sly]

the 93 just got new carrier and pinion bearings with the new gears. Other than that... it's still stock.

[jaywish]

So no whine in the 93?

I get whine after the car is hot crusing down the highway at speed on the pedal or not, it whines.

The axle play I was mentioning on the possible donor was up and down and side to side, not in and out.

[sly]

nope... the clutches make sort of a grinding noise at low speed hard turns... but other than that... it's all peachy.

[jaywish]

I am glad it came out right. I am told that noise will eventually stop as the clutch pads wear in. That long ride home probably did not wear them at all.

I can not remember if we just put in synthetic fluid or synthetic plus the friction modifier or just regular fluid. If the noise does not stop after a good long while you could suck out a bit of oil and add half a packet of modifier.

[sly]

synthetic