I changed the rear differential fluid in my '97 F-150 (3.55 LS) about 2 or 3 months ago. I used the Amsoil 75-140 synth., but I never heard anything about using a friction modifier also. Do I need to put some in my differential(or is it fine the way it is) and does anyone have any preferences in brands. I don't mind ordering stuff through "mail order" and the only parts stores in this area are: Auto Zone, Advance Auto, and Pep Boys. Any preferences in brands/types and where to get it from are apprecieated. TIA

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1997 F-150 Lariat SuperCab 4x4, 4.6L, aoutmatic, Towing package, K&N Filter, Custom Cat-back true dual exhaust with 2 FLOWMASTER Series 40 Delta Flows and 4" x 22" chrome tips(out the back of course).

 

You should have it in there. I got my 4 oz bottle from my friendly, local Ford dealer for about 4 bucks. If your truck is not "walking" you around turns, you may have bad clutches.

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97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-3"
pvc air box mod-Granetelli MAF

 

I have an f350 with danas and posi's front and rear. I just changed my oil out with LUCAS gear oil. I contacted the company via e-mail and they informed me that their product does not require a friction modifier so I used it in my diffs. I haven't experienced any problems with it at all. I's pricey but I think it's worth the money. I think they have a dealer locator on their website.

 

Dana L/S additive p/n: 43161 is available @ your local truck parts distributor. Try your yellow pages. It would not hurt adding the L/S additive, even if you are using Lucas oil stabilizer or lucas gear oil.

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1999 Teal Blue F-150 s/c
4.6L, XLT, 3.55 L/S
Tow pkg., rhino liner, engine block heater & hard toneau cover. single c.d.
255/75 r16 Generals-owl

 

Thanx guys!!! I was told when I changed the fluid to look on the tag on the diff. to see if I needed to use a synth. gear oil, but they never said anything about using a friction modifier also. Well, I used the Amsoil 75-140, and when I read a post about the differential modi. and redlariet replied, I went to the Ford dealer and got some diff. mod.. No noise from the rear end when I added it--but I only put about 1K-1500 miles on it since I changed the fluid.


THANX AGAIN EVERYONE!!!

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1997 F-150 Lariat SuperCab 4x4, 4.6L, aoutmatic, Towing package, K&N Filter, Custom Cat-back true dual exhaust with 2 FLOWMASTER Series 40 Delta Flows and 4" x 22" chrome tips(out the back of course).

 

Pat: How did you get the fluid out of the diff? Did you remove all bolts and replace the gasket, or did you use a hand-pump?

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Black 2000 SC short-box XLT. 4.2 V-6, 5-speed, 3.55 limited-slip. CD, remote entry, factory side steps, rear fender inner splash shields (TSB 00-09-05), FORD box liner.

My third F-series (ordered new). The other two: '73 F-100 Custom, 240 cube 6, 3 on the tree, tan, "West Coast" mirrors, step bumper, knitted vinyl seat, AM radio; and '98 F-150 SC short-box XL, XLS package, Pacific Green, 4.2 5-speed, 3.55 ls, FM-cassette.

GREAT trucks!

 

shifter,
if you have the original fluid, drain it and clean out your case. You may be amazed at the amount of sludge=metal shaving in there.
I've read at the ford-diesel site about guys changing their fluids and being amazed at how bad of shape the ford "lifetime" diff was in.

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http://a1060.g.akamai.net/f/1060/597...b/ff6165cd.gif Dr.(wife says i'm spoiled) Jones.
2000 F-150 5.4L
AUTO,SC-sb 4x4-XLT, 3.55LS, 8.8 front- 9.75 rear, sidesteps, sprayed in liner, 17"wheels ORP, trailer-tow pkg, CD, Cpt chairs, 4whl ABS, Keyless Entry, Airbox silencer removed/K&N, Amsoil(transfercase, motor, rearend), 3" custom dynomax ultra flow catback, as an anniversary gift. With a best of 18.5 MPG.
kjones02@elp.rr.com waiting for the 275hp PSD

 

Local Ford dealer wanted $20.12 per quart for their 75W-140 gear oil in my non-LS F-150. Seems a bit expensive..

I went with the AMSOIL Series 2000 Synthetic Gear Lube ($12.05/quart).

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2000 F-150 XLT, 4x2, 5.4L Supercab, Superchip, Styleside, Black with silver two-tone, 3.55 rear, class III towing package with super engine cooling/auxiliary transmission cooling HD package, Heavy duty shocks, 4 wheel disk ABS, overhead console, sliding rear window, keyless entry, dark graphite interior, in dash CD, factory leather wrapped steering wheel, FORD bedliner, FORD black tubular cab steps, K&N air filter, mar-hyde rubberized undercoating, Modine climate filtration system, Bugflector II, Mobil 1 oil, build 7/2000


[This message has been edited by Dustoff (edited 01-22-2001).]

 

Sorry I haven't been to the boards lately--computer been really messed up...but I don't wanna get started on that!!!

Shifter,
When I changed my diff. fluid at 105K, I did take all the bolts out of the diff. cover, and used a new Fel-Pro gasket. The factory had some stuff like permatex/silicone instead of a gasket, but I prefer to use gaskets when I can. My Fel-Pro gasket was about $6 from Auto-Zone. I used the Amsoil Series 2000 75W-140(paid about $35-$40 for 3 qts). Find a guy named "msparks" on this site--he'll get you what you need.

Oh yeah, don't forget the 4oz. of friction modifier if you have the locking rear end.

Good Luck and have fun

THANKS AGAIN to all who replied!


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1997 F-150 Lariat SuperCab 4x4, 2-tone: white w/tan bottom, 4.6L, aoutmatic, Towing package, K&N Filter, Custom Cat-back true dual exhaust with 2 FLOWMASTER Series 40 Delta Flows and 4" x 22" chrome tips(out the back of course), Bridgestone Dueller A/T's 265/75/16, Ventshade Bug and Window Deflectors.

 

I'm pretty sure that the Amsoil 75-140 already has the friction modifier in it, so you don't need to add it separately if you have the LS rear end. I sure hope that's the case, because I'm running that fluid in both my Expedition and my Superduty, without additional modifier. I haven't had any problems with either one.

By the way, I changed the Expedition fluid at 30,000 miles, and it was a filthy gray mess. I know Ford says it never needs changing, but I wouldn't want to run the factory fill much longer than 30K.

Maybe msparks or someone knowledgable about Amsoil can fill us in on the additive question.


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97 Expedition XLT 4x4, Black, 3.73 LS, 5.4L, leather, all options except LLS, Edelbrock IAS shocks, BFG AT KO 285/75/16s on American Racing Atlas 16x8

 

powerlifter405,

After reading your last post and similar posts from others..I decided to look into my rear differential. You were right...I don't see how this stuff can be considered "good for life". The plug was badly caked with sludge and the factory fluid was a dark grey. I changed mine out with AMSOIL this afternoon.

Thanks for bringing this to my attention!

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2000 F-150 XLT, 4x2, 5.4L Supercab, Superchip, Styleside, Black with silver two-tone, 3.55 rear, class III towing package with super engine cooling/auxiliary transmission cooling HD package, Heavy duty shocks, 4 wheel disk ABS, overhead console, sliding rear window, keyless entry, dark graphite interior, in dash CD, factory leather wrapped steering wheel, FORD bedliner, FORD black tubular cab steps, K&N air filter, mar-hyde rubberized undercoating, Modine climate filtration system, Bugflector II, Mobil 1 oil, build 7/2000

 

This past fall I changed the fluids in my front and rear diffs. using Amsoil. Before I did I called the tech line and asked if I should use the friction modifier. The tech guy said it was not needed. I then asked why that was, what was the difference between your synth diff fluid and anybody elses. The reply was that Amsoil uses better materials and therfore it was not required. I wasn't really satisfied with that answer but followed the recommendation anyway. As of today my rear diff seems to begin locking up for a short period of time while turning a corner either direction from a stop after the drive train has been driven enough to warm up. Cold this does not happen. The only thing I can attribute this to is no friction modifier added when I changed the fluids. Needles to say as soon as the weather breaks I will add the friction modifier and see if there is a difference. As I understand it adding it can't hurt and only costs $4.00 or so. I wish I would have just added it to begin with. Any comments on what I believe is happening is welcomed.

Dave

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'97 F-150 4x4 4.6L Auto Off Road Moonlight Blue
Tow package, Westin Chrome Nerf bars, Color matched bug shield
Linex bed liner, Wizard Ultra White Headlights

 

someone mentioned tha ttheir rear end fluis was a nasty grey mess. It is supposed to be from the factory. Why? Because the gear marking compound is not wiped off. It will not damage anything other than the somewhat strange color. Also the Amsoil guy was blowing smoke up your a$$. All LS's should use some type of friction modifier. No matter the quality of oil, it must have it for proper operation.

 

I just added the friction modifier today and what a difference. Works like brand new. I only hope I have not done any permanent damage to the clutches. MSparks should have a talk to his people at Amsoil about the advice they are giving.

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'97 F-150 4x4 4.6L Auto Off Road Moonlight Blue
Tow package, Westin Chrome Nerf bars, Color matched bug shield
Linex bed liner, Wizard Ultra White Headlights

 

I also meant to ask if there is any type of additive that needs to be put in the front differential(4x4 transfer case). Changed this fluid about 2 months ago and filled with AAMCO DexronIII-Mercon, but have only used 4wd a few times.

--Just curious--
Thanks

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1997 F-150 Lariat SuperCab 4x4, 2-tone: white w/tan bottom, 4.6L, aoutmatic, Towing package, K&N Filter, Custom Cat-back true dual exhaust with 2 FLOWMASTER Series 40 Delta Flows and 4" x 22" chrome tips(out the back of course), Bridgestone Dueller A/T's 265/75/16, Ventshade Bug and Window Deflectors.