How do I know what gear I have in the dif. ?

I want to put synthetic in the dif, what kind should I use.

Don

 

Hey DonW

Ford has a tag on every differential. The tag is hooked to one of the rear cover bolts. If your truck is a F-150 with a 8.8" differential the tag will have the numbers 88 on it and also the ratio for example 3L55.
3L55 means the truck has 3.55:1 gears and the L means it is a locker type diff. Your differential may already have synthetic in it from the factory. There will also be a tag that specifies the use of Ford 75w-140 synthetic axle lubricant if it has synthetic. I am a Ford technician and am a strong believer in the use of factory parts and vehicle care and maintenance products. If you do have a locker and you change the axle lube be sure and add 1 bottle of friction modifier. Good luck, if you have any more questions write back and I will do my best to answer.

 

Don,
Look for the metal tag on your diff. cover(it's held on with one of the bolts). Once you find this you will see some numbers like this: XXXXX XXXXXXX
XXXX XXXXX XXXXX

It's the first set of numbers in the bottom row that give your gear size. Ex1 3L55, means 3.55 to 1 ratio with Limited slip. Ex2 3 55, means 3.55 to 1 ratio with out LS.

As far as your synthetic lube question, I don't know. I'm not planning on changing it till I have a problem or the manual says to change it.

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stock 98 XL, Reg. cab,4.6, Auto, Tow package, 255/70R16 on styled steel wheels,3.55LS, Black with chrome grille and bumpers! MODS: custom stereo by me, building speaker box was a !@#$%. K&N air filter w/ airbox mod, a complete keyless entry system.

 

fordfixer. I have a question. I recently pulled the rearend cover to change the fluid. I noticed a thin gear bolted to the ring gear thats about the same diameter. Could you tell me what it's for?

Thanks, Henry.



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99 F-150 XL 4x4. RC Flareside 4.6 5spd, 3.55LS. gibson 3" cat-back, K&N Gen ll.Westin step bars.Ventshade window deflectors and bug deflector. rhino liner and a cool white shifter ball.

 

Harry, that ring that your speaking of, is for the rear abs. If you look on the front side of the differential, you'll see a sensor threaded into the case, with the wiring comeing out of it

 

Hey Harry, Rich is right. Ford calls this "gear" a tone ring or excitor ring. The space between each tooth is the same. When the tooth passes the rear speed sensor it sends a signal to the abs module which compares it to the front speed sensors if equipped with 4wabs. In a lock up situation the module sees that the rear sensor is not sending out the signal and activates the abs.

 

Thanks. I couldn't figure was it was for. Now I'll have to look for the wiring.

Henry.

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99 F-150 XL 4x4. RC Flareside 4.6 5spd, 3.55LS. gibson 3" cat-back, K&N Gen ll.Westin step bars.Ventshade window deflectors and bug deflector. rhino liner and a cool white shifter ball.