Strange roaring noise

[Eddie Greenlee]

Good morning and thanks for your help in advance.
I just bought my first 97 Jeep Wrangler tj, and im hearing a noise under the jeep when im driving. The faster i go the louder it gets. When i let off the gas it stops. SO this morning im going into the difs to inspect and change the dif oil. when i go back should i use regular or synthetic oil? I may have other issues so please feel free to ask or give advice .
again thanks

 

[Stinger]

There are some different reasons for the noise source that based on the information you have given it would be impossible to give an accurate guess. However, noise that changes during acceleration/ deceleration may vary we'll be a ring and pinion issue.
For diff fluids: if you anticipate being in there often use Dino fluid, it's cheaper. However, if all is good and there is no need to pull the cover I would use synthetic. I use Royal Purple 74/140. Having said that several years ago I had Northridge 4x4 change out my rear R&P. The tech ( Dave Johnson is the owner, his father set up my gears) put in MOPAR factory fluid and told me there was no reason to use anything else.

 

[Chris]

@Eddie Greenlee

I would use synthetic, but I don't think that's going to make the difference. Does the noise sound like metal-on-metal at all?

If there was a noise coming from the rear end my first thought would be the differential. I would take the cover off and inspect things. That's likely your culprit.

 

[david]

if you disconnect the front drive shaft you may be able to narrow it down.

 

[Eddie Greenlee]

ok, just saw yalls replies. I did take the cover off the rear today and inspect the ring gear, pinion. and spider gears. from what i could see the ring gear looked great the blades were flat (nothing worn to a thin sharp edge) and looked brand new to me. I did notice the pattern and it looked a little high from what ive seen on youtube and other patterns. the back lash was some where around .009 to the best of my ability. i cleaned everything very well with brake cleaner and put the cover back on. I didnt realize i had to wait 24 hours before i could put the oil back in. but anyway ill take it out for a spin in the morning.

 

[Eddie Greenlee]

why the front drive shaft David???

 

[david]

why the front drive shaft David???

I was thinking it wouldn't be turning but I have lockouts

 

[Chris]

I'm assuming you're 100% positive the noise is coming from the rear?

 

[Eddie Greenlee]

we are 100% sure the loudest of the noise is coming from the rear of the jeep for sure

 

[Chris]

we are 100% sure the loudest of the noise is coming from the rear of the jeep for sure

I would say it's definitely differential related then. I suppose it could be driveshaft, but that seems unlikely if it's a loud roaring noise.

 

[Eddie Greenlee]

hey i took my jeep to a professional transmission/4x4 shop today. the owner rode with me and listened to the roaring while I was on the gas. Then we came back to the shop and he jacked up the rear end and had me run the jeep up to about 50 mph and there was no doubt the noise was coming from the rear end. So he said "for some reason the ring gear and pinion are out of sink somewhat, causing the loud roar. He gave me the price to fix my problem, and i had to leave $$$$$ . anyway im driving it like it is for now , while getting up the nerve to do it myself. haha
.

 

[Stinger]

hey i took my jeep to a professional transmission/4x4 shop today. the owner rode with me and listened to the roaring while I was on the gas. Then we came back to the shop and he jacked up the rear end and had me run the jeep up to about 50 mph and there was no doubt the noise was coming from the rear end. So he said "for some reason the ring gear and pinion are out of sink somewhat, causing the loud roar. He gave me the price to fix my problem, and i had to leave $$$$$ . anyway im driving it like it is for now , while getting up the nerve to do it myself. haha
.

Its easy to fix IF you know what you are doing. Its a bitch and very easy to screw up if you don't. But ya know--ya got to start sometime. Do A LOT of research and have the proper tools before you start.
Good luck

 

[Eddie Greenlee]

thanks, Stinger. I would really like to work with someone that knows what they are doing. but not many shop owners will invite you in for a lunch and learn ha. I think it would be fun to learn how to do, because its so technical .

 

[mrblaine]

. I didnt realize i had to wait 24 hours before i could put the oil back in. but anyway ill take it out for a spin in the morning.

You don't. I use Mopar Diff sealant and smear it on, bolt it up, fill it with gear oil and go drive it. Never leaks.

 

[Stinger]

You don't. I use Mopar Diff sealant and smear it on, bolt it up, fill it with gear oil and go drive it. Never leaks.

Same here. Never had a leak.

 

[mrblaine]

Same here. Never had a leak.

It is another of those things that folks generally think are all the same but aren't. There is a popular aftermarket t-case builder that needed a RTV product that worked perfectly every time and after a whole bunch of testing, they settled on the Mopar Oily Surface RTV that we use for diff covers. The only time I don't use it is for transmission pans without gaskets. For that I use the black Mopar for transmission fluid and it has solved several problematic pan leaks for me. Over the years I've bought and used at least 60 tubes of the diff stuff with never an issue.

 

[Eddie Greenlee]

in an effort to save a little money, will it work to take a ring gear and pinion out of another axle and install it in my jeep. I found a guy that has a 411 ring and pinion for sale.

 

[Stinger]

That may work. BUT having been a drag racing teenager many years ago I found that reinstalling used R&P just didn't work well. Just never could never get those gears back into exactly the same alignment as their wear pattern had been worn.
Good luck--seriously. Please post up your results.

 

[Eddie Greenlee]

i think ill stay away from it then.

 

[Chris conner]

Did you ever get the issue fixed? Bc my 97 started making the same noise you described.