Rear End

kreil45 · Jun 21, 2012

I have an 03 GT auto with play in the rear end causing a clunk. The tech said that is probable the spider gears. The rear end is stock and i want to do 373. What should i do? should i have him rebuild it or can i put a rear end from a explorer in it or is there a company that sales already built with 373s?

wmburns · Jun 21, 2012

FWIIW, a clunk especially when sifting from forward to reverse is usually U-joints.

I would strongly recommend against swapping out the entire rear end from another car. You are going to find out things like the half shafts are different lengths and the ABS tone rings are different as well as the speed sensors.

Besides if going to the trouble of replacing an entire axle, there will never be an easier time to rebuild it while it's on the bench.

Anybody that is able to rebuild a rear end could also install new gears.

But I wouldn't pay anyone to rebuild my rear end if they can't tell the difference between worn U-joints and "other" rear-end problems. Further, I find it hard to believe that the spider gears can wear out without there being other bearing wear.

If this were my car I would inspect the the rear end and see for myself what the real problem is. You will be surprised how much rear end trouble shooting that can be done with a simple visual inspection of what's behind the cover and the condition of the oil.

kreil45 · Jun 24, 2012

wmburns said:
FWIIW, a clunk especially when sifting from forward to reverse is usually U-joints.

I would strongly recommend against swapping out the entire rear end from another car. You are going to find out things like the half shafts are different lengths and the ABS tone rings are different as well as the speed sensors.

Besides if going to the trouble of replacing an entire axle, there will never be an easier time to rebuild it while it's on the bench.

Anybody that is able to rebuild a rear end could also install new gears.

But I wouldn't pay anyone to rebuild my rear end if they can't tell the difference between worn U-joints and "other" rear-end problems. Further, I find it hard to believe that the spider gears can wear out without there being other bearing wear.

If this were my car I would inspect the the rear end and see for myself what the real problem is. You will be surprised how much rear end trouble shooting that can be done with a simple visual inspection of what's behind the cover and the condition of the oil.

the u-joints are brand new as well the tranny mount. the guy i took it to is pretty much a trans specialist. so, he ruled out that. he says he found some play in the rear end (also had the clutches done by some one esle who said that would fix the problem no charge when it didnt)

trinity_gt · Jun 24, 2012

kreil45 said:
I have an 03 GT auto with play in the rear end causing a clunk. The tech said that is probable the spider gears. The rear end is stock and i want to do 373. What should i do? should i have him rebuild it or can i put a rear end from a explorer in it or is there a company that sales already built with 373s?

I strongly doubt it's the spider or side gears. These see relative motion only when you're turning. and even then the rotation rate is so small (dictated by the difference in speed of the road wheels) that wear is practically unheard-of.

When do you hear the clunk? Under what conditions, specifically, do you hear noise? Turning? Accelerating? Decelerating? Just starting? Just stopping? Transition from drive to coast?

If you are intent on going to 3.73s then the ring and pinion are going to be swapped anyway and you'd be wise to invest in a kit of parts that includes all new bearings and races. As long as the rear hasn't been run dry the side and spider gears should be fine.

But you should make sure that the clunk you're hearing is not related to the control arms, bushings or even the mounting points on the chassis and floor behind the rear seats...

kreil45 · Jun 24, 2012

trinity_gt said:
I strongly doubt it's the spider or side gears. These see relative motion only when you're turning. and even then the rotation rate is so small (dictated by the difference in speed of the road wheels) that wear is practically unheard-of.

When do you hear the clunk? Under what conditions, specifically, do you hear noise? Turning? Accelerating? Decelerating? Just starting? Just stopping? Transition from drive to coast?

If you are intent on going to 3.73s then the ring and pinion are going to be swapped anyway and you'd be wise to invest in a kit of parts that includes all new bearings and races. As long as the rear hasn't been run dry the side and spider gears should be fine.

But you should make sure that the clunk you're hearing is not related to the control arms, bushings or even the mounting points on the chassis and floor behind the rear seats...

I both feel and hear the noise. Its most present when i let on and off the gas at around 40-45. I also just replaced the rear lower and upper control arms with UPRs. while it was up in the air we turn the rear wheels foward and back ward and there was alittle noise and movement coming from the pumpkin. I had it at a shop that aslo literaly took off the whole rear suspension and rear axle and could not find anything. Maybe i should just have the rearend rebuilt just to rule that out.

flstang65 · Jun 25, 2012

I put a new rear out of a another car and it was nothing but a nightmare. Trying to get axles that were the right length, the mounting flanges for the caliper brackets were bent, took me forever but, I finally got her straightened out.

Sean Fuller · Jun 28, 2012

flstang65 said:
I put a new rear out of a another car and it was nothing but a nightmare. Trying to get axles that were the right length, the mounting flanges for the caliper brackets were bent, took me forever but, I finally got her straightened out.

Hey guys,
I have my 1999 GT in the shop with a metallic grinding noise that is sourced to the rear end (numerous mechanics have told me this). The noise occurs when deaccelerating in 3rd and loudes in 4th...that's when its noticeable. I've change the fluid and this time had a complete rebuild and 4.10 gear from Ford installed. I thought, "ok, this will be gone" only to have the shop call me and say they finished a second rebuild reinstall of the gear (they thought the grinding noise was something they did, but it just reappeared even with the new hardware!) They are stumped, and so am I. Thought I could reach out to my fellow mustang brethren for any kind of suggestions. I can pickup the car tonight (new springs/struts, clutch, the 4.10s,) but they dont think they can identify it, which is very dissapointing. I'd hate to drive away with all the new goods and that same grinding noice.

Any ideas?
Thanks!

Rear End

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