3.25 Traction Loc issue in curves and corners.

[Fordboy71]

So I finally got to take the 71 out last night for a rest drive. First drive since I towed her home a year ago. The car had been sitting for years.

When going around curves and corners the rear end feels like it “catches”   That’s the best way I can describe it.

I get a clunk and a side shift from the rear. It’s fine going straight. No traction problems or slippage. At first I thought it felt like a sticking brake shoe or how it feels when turning with a stuck caliper. But now I’m sure it’s in the rear. 

I was thinking I should start with new fluid. I am also going to replace the worn out leaf springs and shackles. I’ll probably also get rid of the air shocks the previous owner installed. 
Does this sound like a good place to start? 
What fluid is best. 
This is my first Trac-Loc Ford. 
Thanks. 

 

[Fordboy71]

Also..I see there are replacement leaf springs in 4 OR 5 leaf. Which ones will give a better ride? 

 

[Bentworker]

Are you sure you don’t have a locker?

Other thing is are you running limited slip additive in your gear oil?

 

[Stanglover]

Perhaps I can offer something here. This year, I had my rear axle serviced and added a traction-loc dif. because 'the price was right'. I too have a 3.25:1. I think what is happening is the clutches are sticking in the trac-loc. You might first try to add a 4 oz bottle of Ford friction modifier, you can easily get that from a Ford dealership service counter. If that does not free up the clutches, a service may be needed. I'm far from an expert on these, but on mine, I get no clunking sounds. It may also need to be driven a bit more, but gently!! There may be other additives you can use, not sure on that though. As for oil, Valvoline 80W90 gear oil is what I use plus the Ford friction modifier. It took about 2 1/2 bottles to fill to the correct level. TIP; warm the bottles in hot water before as it's like tar to pour otherwise. Also the friction modifier stinks to high heaven, don't get it on your hands or clothes.

As for springs. I am in process of changing mine. I have posted on this before including YouTube videos from Eaton Detroit Springs. When I first swapped out my rear springs, I chose Grab-A-Track 4 1/2 leaf springs at 175lb spring rate to help eliminate spring 'wrap up'. What I found was they were too arched and put the rear end way up too high. I later had then de-arched, but then they started to reverse and are now too low. So, back to the drawing board so to speak, I have ordered a set of Eaton Springs Boss 351 4 leaf springs @ 153lb spring rate. With my 7/8" anti sway bar, I think the handling will be right where I want it, firm, but not bone jarring. I am currently using KYB Gas-A Just shocks, but I am planning on returning to good oil filled shocks. Air shocks are not good on our cars as they were never built to work with them. You can probably get Eaton Springs from NPD or directly from Eaton. IMO, don't waste your money of anything else.

Stock spring rate for Mach 1's and 429's was 138 lb, others were softer, so check your needs.

 

[Stanglover]

Are you sure you don’t have a locker?

Other thing is are you running limited slip additive in your gear oil?

As in "Detroit Locker". Not meaning to correct you, just clarify.  Limited slip or friction modifier was my first thought too.

 

[Jeff73Mach1]

4.5 leaf springs would be my choice. (I have 5 leafs and they are stiff and can be punishing)  I concur that what you feel may be a locker rear end where the spider gears are welded, but it also might be the front spring bushings being shot allowing the rear end to move laterally.  Your plan is reasonable as all will need to be done at some point anyway.  If it is a Traclock rear end the clutch pack may need to be rebuilt.  If you can pull a chunk, the next steps aren't bad at all.

 

[Stanglover]

4.5 leaf springs would be my choice. (I have 5 leafs and they are stiff and can be punishing)  I concur that what you feel may be a locker rear end where the spider gears are welded, but it also might be the front spring bushings being shot allowing the rear end to move laterally.  Your plan is reasonable as all will need to be done at some point anyway.  If it is a Traclock rear end the clutch pack may need to be rebuilt.  If you can pull a chunk, the next steps aren't bad at all.

Jeff, looking at the Marti Tag Book, the only difs listed with Detroit Locker's are the Boss 302, code WFU-E, same for the 428SCJ, 429 SCJ. All others  with an L in the ratio code would be Traction-Lok I'm assuming. His door tag may give a hint as to what he has if it's original. Of course, someone may have swapped out the rear end for a D/Locker. If that is the case, definitely time for a rebuild.

 

[c9zx]

This may help you determine if you have a Detroit Locker. https://explorationoutfitters.com/pages/detroit-locker-faq

If it is not a Detroit Locker, but is a Traction-Lok friction modify (Motorcraft XL-3) may not have been added after a clutch pack exchange. Too much pre-load on the clutch pack will cause tires to chatter during a slow speed turn. Chuck

 

[Hemikiller]

Easy way to tell a Detroit Locker is to do a tight circle in a parking lot. DL will have a very obvious metallic "click" to it as it releases. If you don't hear a clicking, and the rear just feels like it's binding up, then you probably have a Traction Lok. The friction modifier others have posted *should* help. Many gear lubes state they have it in there, but it's not what works for a Ford clutched unit. 

I have the 138lb factory 4 leaf 429CJ springs in my Mach 1 and like the ride. 

 

[MKSpeedlab]

As others said, my first thoughts was maybe the previous owner put a locker in it. Usually with one you can feel it kinda ratcheting around corners and definately notice a rear tire grabbing. If it was a welded diff like Jeff mentioned it would likely chirp tires around any corner but you dont usually feel/hear any ratcheting since welding it basically turns it into a spool so it wouldnt have any give. So my best guess is locker or as others have mentioned maybe your diff needs a bottle of friction modifier.

 

[Fordboy71]

Thanks everyone, sorry it took so long for me to get back. Long workday. The door plate on my car has an R code. My Marti report says is a 3.25 traction lok rear axle. When I jack up the rear end both wheels turned forward. But you cannot hear a ratcheting Or chirping when going around corners or in circles in the parking lot, so I’m guessing not a DL. This weekend I’ll change the fluid and add a friction modifier when I put a new spring kit in. 

 

[Bill73Ragtop]

Make sure you use petroleum-based rear end gear oil and not synthetic.   Trac-Loc clutches do not like synthetic.

 

[c9zx]

Bill, Did you have a bad experience with synthetic gear lube? Have used Amsoil synthetic gear lube in several Traction-Lok units with no problems. I've used in street cars, drag cars, and a couple that saw occasional road course use. Chuck

 

[Fordboy71]

Got the differential out today. Things were going smoothly until it got to the 10 center section bolts. Two things I learned...1. Don’t put the jack stands under the axle. 2. Don’t try to remove the center with a 7/8 rear sway bar mounted in the car. That added an hour to the job fighting the #@!: sway bar. Everything looked super clean inside. If I had to guess, I’d say the previous owner had it rebuilt and didn’t add the friction modifier.
 There were copper washers at each lock nut on the center. Are these very important? Should I put new ones on when I reassemble it?
Thanks again for all the help everyone. 
 

 

[Bill73Ragtop]

Bill, Did you have a bad experience with synthetic gear lube? Have used Amsoil synthetic gear lube in several Traction-Lok units with no problems. I've used in street cars, drag cars, and a couple that saw occasional road course use. Chuck

About 10 yrs ago after doing a rebuild with new clutch pack, I tried synthetic gear oil (Pennzoil or Valvoline as I recall) with the thought I'll never need to deal with it again.....after putting approx 1000 miles (with no issue) the rear end started grabbing in turns & reverse with noticeable groaning.  Driving forward in straight line did not appear a problem.  Within a couple hundred miles the noise & grabbing became "time to fix!".   The fix was simple, pull the differential to drain and clean out the pumpkin, spray differential with brake cleaner, re-install and fill with petroleum based. Immediately upon backing the car out of the garage for test drive, all issues were gone.

Unfortunately I also encountered a similar problem with a Detroit Tru-Trak I installed in my 69 vert in 2006 using synthetic.  No clutches so I figured it was simple decision to use synthetic.  First 6K+ miles were no problem and then it began to groan in reverse / turning.  When I called and talked to a tech at Detroit Locker, he admitted they were having some issues with synthetic.  He recommended pulling it and washing it down with carb / brake cleaner and re-installing.  Now, unlike back in 2006, the description on the Summit site for the Detroit TruTrak notes you need petroleum based gear oil.

Considering that petroleum based is readily available and a proven lubricant, my personal recommendation is to use for differentials in vintage setups.  If the differential manufacturer recommends something else (for those using new setups) follow their direction.

NOTE: Fordboy 71 - you should be able to pick up replacement copper washers at Home Depot / Lowes .  I would re-install them.

 

[Stanglover]

Just a note on the center section bolts/nuts. My dif. builder strongly recommended using NEW  grade 8 3/8-24 flanged nuts and copper 'crush' washers as they're called. Torque spec he gave me is 45 ft/lbs done in 3 steps to ensure even torque. Strangely, he was out of stock for both nuts and washers, so I had to get my own..

Note on "flanged nuts"; they can be bought in self locking  or plain, you need plain ones when using crush washers.

 

[Fordboy71]

I’ll grab some new ones. Thanks!

 

 

[Carolina_Mountain_Mustangs]

It takes some getting use to even a traction loc. You can drop the clutch and do 180 deg. and not move forward. A Detroit locker is even worse. You have to learn how to drive a traction loc I use to scare my daughter and her mom to death. Was fun. 

 

[Fordboy71]

I’m putting her back together tonight! Since I don’t want to do this job again. The plan is to put on the new copper washers with a new gasket and a light film of black or gray RTV on each side of the gasket. Does this sound like a good plan? Or is it better just to put the gasket on dry?