Jag Rear "clunk"

[Russ Dickey]

I did a quick search on "jag rear" and didn't find the answer, so I'll post this question as a new thread:

I've got about 6700 miles on my FIA now. Just recently, I (as well as my passengers) have noticed a very slight "clunking" noise coming from the rear end. This happens upon initial release of the clutch from a standing stop, and even sometimes as the car is coming to a halt under braking. In addition, I've heard this noise when turning a corner. It's only noticeable at very low speeds, and it's pretty quiet, but nontheless I want to try and figure out what it is so it doesn't get worse.

I crawled under the car this past weekend, and noticed a bit of brownish-colored fluid on the bottom of the pumpkin section, but couldn't locate the source. Due to it's color, I am assuming it's differential fluid, but nothing appeared to be loose. I'm headed over to a friends house who has a lift so I can give it a closer inspection. Any advice from you guys on things I should specifically be looking for??

Thanks,

Russ

Unique 289FIA - Viking Blue

[eliminator]

Russ,

If you have an Auburn Unit (Anti - Spin) unit in the rear-end that's the orgin of the noise. When you are turning there are cone like clutches sliping so one turns more than the other and they make alot of racket. The braking noise I don't know about. When I release the clutch on mine, hard, not easy I have always had that "clunking" noise, I have always thought that to be the Auburn unit also. Adding more Friction Modifier will help and with 6,700 miles it's ready for a rear differential fluid change if you havn't done so.

Rick
#4279405

[ralphscott]

Russ, I had the same problem when turning a corner at low speeds. Butch Capps who built the rear end suggested that I add an additional tube of the positraction additive (for a total of 2 tubes) and it helped a lot. It is very disconcerting when you first hear it and you are miles from home. It is one of those "Aw $#i+!" moments.

Ralph

[Brent]

I have a Butch Capps prepared 3.54 with an Auburn posi and I have not experienced this yet. I do have 2 bottles of friction modifier in mine. ???????????

Brent

[pgermond]

Maybe someone can enlighten me..... I did experience an occasional "clunk", mainly in the left (driver side) rear at low speed making a right turn initially. I have the Power-Lock upgrade with my 3:31. Is this the Auburn posi that is being referred to?

I added (almost all of) a 4 oz. tube of Equa-Torque Limited Slip Additive when I assembled the car. Haven't heard anything lately. Am I on track here?

Thanks!

Phil

427 Roadster, #4279436
Southern Automotive FE
3:31 and Toploader

Roseville (N.Cal)

[ralphscott]

Phil, you are on track. I have the posi and a 3:31 as well had to add two tubes.

Ralph

[pgermond]

And the Auburn unit?

Phil

427 Roadster, #4279436
Southern Automotive FE
3:31 and Toploader

Roseville (N.Cal)

[ralphscott]

Phil this may be a little long but here goes I go this from Butch Capps:

Check your rear end if there is a metal tag on it it will tell you what you have:
O -- open
L -- locker
PL -- Power Lock
A -- Auburn (may also have HP or Pro in addtion to the A
there is also a serial number and if you send it to me I can get Butch Capps to provide additional info for you.
If there is no metal tag then Butch more than likely did not build it. If that is the case and it is a posi it is more than likely the Dana Power Lock as that was the standard Posi that was used in the Jags. The Auburn is an aftermarket unit that was used when there were no Dana's to be had (they do 1 run a year for the Dana PL).
The differnce between the Dana and the Auburn is that the Dana uses clutch plates and the Auburn uses a cone. There are other differences but that is the main one. Typically you use 1 tube of anti friction in the Dana and 2 tubes in the Auburn. If you have to use 2 tubes in the Dana that is OK. The Auburn will regardless of the amount of anti friction additive will make noises at slow speeds when backing in a tight turn, just the nature of the beast.

Also if you have not changed the fluid in the rear end after the first 500 - 1000 miles do so.

Hope this helps I have a Dana in mine

Ralph

[pgermond]

Thanks Ralph - here's what is on the metal tag:

MCGS 6013 (???)
R 3.31 (3.31 ratio, don't know what the R stands for)
PL (I assume power lock)

Sounds like it's time for a gear oil change (1,000 mi)

Phil

427 Roadster, #4279436
Southern Automotive FE
3:31 and Toploader

Roseville (N.Cal)

[ralphscott]

Phil I'll try to get the info to you tomorrow. Your interpetation on R and PL are correct.

Ralph

[ralphscott]

Phil, talked with Butch this morning and here is the scoop and some advice:
MSGS = Mid South Gear Specialties
6013 = built in a production run on 02/17/03
It is a new Power Lock unit 19 spline with new seals and ball bearing stub axles. You should use 2-4oz bottles of anti-friction. Butch uses Dana and if you call him he will UPS two bottles to you $8.50 a bottle 865-524-4800.

As for oil DO NOT use synthetics I use Exxon Superflo GX 80/90 1.5 quarts. Butch uses that and Valvoline. Other oil MFG's are OK as long as there is a GL 5 on the bottle. Otherwise you will get foaming that will leak out your vent on the top of the unit. When you pull the magnetic plug at the bottom of the unit you will see gooey thick accumulation on the plug. That is normal as it is the grease from the assembly process. Use a 1/2 inch square drive. After the first oil change you can go 5-10,000 miles between changes unless you do track events then you need to change out the 1.5 qts after each event.

So there you have it.

Ralph

[pgermond]

Ralph thanks for all the information. A lot more than I expected and very much appreciated. I'll give Butch a call.

Thanks again ;)

Phil

427 Roadster, #4279436
Southern Automotive FE
3:31 and Toploader

Roseville (N.Cal)

[ralphscott]

No problem Phil. I'm sure Butch enjoyed talking to you and knowing where his handi-work ends up. He is a real craftsman. The second part I brought for my Cobra a year before I even ordered the kit was a close ratio toploader from him. I consider him a very close friend. I, like so many others, have learned a lot from him. :D

Ralph

[davids2toys]

I have the same clunk, I thought is was the heim joints binding up in the travel arm ends, and that is what I was told by a few people. I have lube them but still have the noise. This rear was rebuilt to 354 gears by the previous owner back in 96, I am looking at the receipt and it says one bottle of additive. As far as I know I have Salibury unit with dana gears. Can somone give me the amount of fluid with the additive I should have...maybe even the proper proceedure for changing it.
Thanks...Dave

[ralphscott]

Look up 4 messages or so above this one dated June 17

[davids2toys]

I saw that but I did not want to make the assumption that everybody car gets the same.
So this is the first Jag rear in my life.I have a 12 inch x 12 inch plate on the bottom of the rear, I think I see a plug underneath. So , if this is the plug, I need to remove this skidplate,then I will drain it, then on filling it, is it till it flows out of the filler in the middle of the cover? Do you do this hot or does it matter.
I have a 1 quart of Moroso climbing fluid( it does say GL-5), and 8 ozs of Amalie limited slip additive concentrate.
This was given to me last year by a good friend with an ERA. It was recommended to him and he liked it. It would be nice if I could just by another quart of the Moroso and be done with it.
What do you think?
Thanks

[ralphscott]

I remove my plate before I pull the plug. I also like the fluid warm cause I've always done it that way and it works for me. As for additives I use what I stated as it was suggested to me by Butch Capps who builds these rearends I put a premeasured amount in the chunk. I try to keep it as simple as possible.

Hope this helps.

[davids2toys]

Yeah, it would be pretty hard to do with the skid plate in place...lol.
So, is the fill hole the hole about midway up the cover to the right side, do you keep putting it in until it flows out of the hole?

[eliminator]

Use Valvoline 75/90, no synthetic and the additive you have. Do not overfill, as soon as the gear oil starts to run out thats it. Actually if you can touch the gear oil when you put your finger in the fill hole it's perfect. I am sure there are other gear oils that are good but Butch Capp's reccomends the Valvoline and it's readily available.

[davids2toys]

Thanks, I actually ordered another qt of the Moroso already, expensive stuff, 14.00 a qt.
As far as the full level goes, my 05 mustang calls for 1/2 below the hole for the tranny. So with these rears, is it flowing out of the hole or a certain distance below the hole.

[Jim Harding]

[QUOTE=ralphscott;63020]with new seals and ball bearing stub axles. QUOTE]

Man I hope that's not the case. Ball bearings are the achilles heel in Jag rears. They were only used a couple years (around 1968) and were soon replaced by tapered roller bearings. Replacement ball bearings are almost non-existent nowadays, and if you find a set, expect to pay upwards from 400 - 500 bucks a set. My older car is still up on blocks as a result of the ball bearings going up. I've got a lead on solving my problem, but I sure hope you don't have to go down that road.

[Tony Radford]

I haven't done anything with the rear end in my car for 25K miles. Do I need to be doing something? It contains whatever Unique put in it.