Help with 9" Trac lok
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Cargo Master
Joined: Apr 2005
Posts: 3,338
Likes: 167
From: Harpswell Maine
Help with 9" Trac lok
I normally do essentially all of my own work, however in the case of setting up my 9" with trac lok I did have a friend of a friend assemble with new r&p and new trac lok parts. That was a number of years ago. The truck when turning feels like the rear is alternately trying to lock up, particularly at slower ,speeds, like it is "walking around the corner" It has the correct amount of friction additive and fluid, new bearings and is properly quiet going straight down the road. I thought that it would "wear in". That has not happened. I am about at the point of going back to a non trac lok setup. Your thoughts and recommendations?
Post Fiend
Joined: Feb 2001
Posts: 6,328
Likes: 124
From: Iowa
The "stickiness" can definitely vary. You have a torquey motor and a light rear end. With time it might wear in,, but that might be too long for you. I would add another bottle of additive and use a good brand. My differential guy has always put an extra bottle in when he installs new gears since forever. It won't hurt to try. Otherwise you are disassembling to have a look inside.
Fleet Mechanic
Joined: Jan 2004
Posts: 1,688
Likes: 1,471
From: Mendon, Massachusetts
My 49F1 has a trac lok and defiantly makes a lot of unwanted noise while turning at slow speeds.... the clutch pack is slipping on the steels as you turn which is normal. If you still have a stock type suspension (spring & hangers) the friction from the slipping clutches resonate through the whole truck. Only solution I can think of would be to replace the spring & hanger set up with newer poly/rubber bushings to isolate the friction noise or install an open differential. I'm considering pulling the Trac Lok on my 49 but for now just putting up with slow noisy turns.
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Cargo Master
Joined: Apr 2005
Posts: 3,338
Likes: 167
From: Harpswell Maine
Thanks for your responses. I will add another bottle of friction modifier. My reading indicates that once broken in (which I should be by now) the running torque should be in the 100-250 ft lbs. I assume that means I could test by jacking up one rear wheel, firmly blocking the other rear wheel,fabricate a 3 legged spider that bolts to the rear axle with a large nut in the center welded to the spider and use a torque wrench to measure moving/running torque. The pain would be that my access (my son) for a high load torque wrench is the click type. I do have an old sears dial type but not a high enough torque capability. Has anyone gone down this road and tested on the vehicle?
Logistics Pro
Joined: May 2015
Posts: 4,475
Likes: 974
From: Tri Cities, TN
That 100-250 ft. lbs. is the bench torque with new plates. After it is broken in the torque is 40 ft. lbs. min. It is possible it wasn't shimed right when it was assembled or it didn't get broken in. The easiest way to break one in is to drive to a parking lot and drive in tight left an right circles for 10 minutes or so.
One other thing, you don't ever want to put synthetic gear oil in a clutch type locker. That stuff will cause it to chatter even with friction modifier in it.
One other thing, you don't ever want to put synthetic gear oil in a clutch type locker. That stuff will cause it to chatter even with friction modifier in it.
Last edited by Crop Duster; May 22, 2021 at 12:46 PM. Reason: More words
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Elder User
Joined: Apr 2016
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I normally do essentially all of my own work, however in the case of setting up my 9" with trac lok I did have a friend of a friend assemble with new r&p and new trac lok parts. That was a number of years ago. The truck when turning feels like the rear is alternately trying to lock up, particularly at slower ,speeds, like it is "walking around the corner" It has the correct amount of friction additive and fluid, new bearings and is properly quiet going straight down the road. I thought that it would "wear in". That has not happened. I am about at the point of going back to a non trac lok setup. Your thoughts and recommendations?
If the fluids are correct, I've seen one instance where the clutches were not soaked in oil during assembly and were dry. The cure was to do some donuts in an empty lot to get oil into the clutches.
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Cargo Master
Joined: Apr 2005
Posts: 3,338
Likes: 167
From: Harpswell Maine
Iirc I used the Ford additive. I see 2 different "Ford" additives, the Ford racing in a white container, CM-19546-A1, and Motorcraft XL-3 in a red, black and white container. Which is recommended?
I made a torque multiplier which with my old Sears beam torque wrench will give me up to 200 ft-lb. I thought that I would measure the running torque with both wheels off the ground and then block one wheel on the ground and measure that running torque. I think that the difference will give me the equivalent of the "bench" torque. Yes?
I made a torque multiplier which with my old Sears beam torque wrench will give me up to 200 ft-lb. I thought that I would measure the running torque with both wheels off the ground and then block one wheel on the ground and measure that running torque. I think that the difference will give me the equivalent of the "bench" torque. Yes?
Post Fiend
Joined: Feb 2001
Posts: 6,328
Likes: 124
From: Iowa
You can read internet debates about synthetic vs conventional GL for weeks if you care to. After 30 yrs in the street strip cars of mine and friends with Mobil 1 and Redline I've decided it's internet lore. Synthetic certainly isn't required though. I always use additive though, even if the product says it's not necessary. It is possible as crop duster mentioned that clutch and shim pack is not correct. I've met a few guys that believe they have a better answer adding a clucth and or steel. . I'd run it by your gear setup guy if another bottle of additive doesn't make a difference after you drive in tight circles for awhile. I bet that will make a notable difference but we'll see.
Thread Starter
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Cargo Master
Joined: Apr 2005
Posts: 3,338
Likes: 167
From: Harpswell Maine
Iirc I used the Ford additive. I see 2 different "Ford" additives, the Ford racing in a white container, CM-19546-A1, and Motorcraft XL-3 in a red, black and white container. Which is recommended?
I made a torque multiplier which with my old Sears beam torque wrench will give me up to 200 ft-lb. I thought that I would measure the running torque with both wheels off the ground and then block one wheel on the ground and measure that running torque. I think that the difference will give me the equivalent of the "bench" torque. Yes?
I made a torque multiplier which with my old Sears beam torque wrench will give me up to 200 ft-lb. I thought that I would measure the running torque with both wheels off the ground and then block one wheel on the ground and measure that running torque. I think that the difference will give me the equivalent of the "bench" torque. Yes?
I then bought a bottle of the Ford Racing additive (white container) . I drained the rear and refilled with fresh conventional gear oil plus the Ford Racing additive. I could tell already that it liked that additive better than the previous additive that I used. I then did the 10 minute circle game. Now no more rear grabbing. I measured the breakaway torque again, still a little high at 100 ft#. What I found online ranges from 40-75 ft#. I am going to live with it since it no longer "talks" to me. Thanks to all for their responses.
Fleet Mechanic
Joined: Jan 2004
Posts: 1,688
Likes: 1,471
From: Mendon, Massachusetts
Finally got around to changing my Ford 9" gear oil (85-140W conventional & w/ Ford racing friction modifier) ..... took it for a spin, did some tight circles and now NO more noisy Trac-Lok!
Thanks to the guy's who posted their advice on this thread
!!!
Thanks to the guy's who posted their advice on this thread
!!!
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Chris-R
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Oct 5, 2009 10:39 PM