I have a 1992 5.0L F-150 4x4 AOD with about 60K on it. Ever since I purchased this truck new in the winter of 1991, I have had a problem with a vibration and pinging after the transmission shifts into overdrive especially under load. I'm pretty sure the differential gearing is somewhere in the 2.70's. If I manually pull it back down into "D" it does get somewhat smoother. Also, something else I've noticed is that I never "see" a second gear. It's either 1 (first) and then D (drive) and then OD. I've had the shift points checked by a Ford authorized mechanic and they are where Ford says they should be. Anybody have/had this same problem ?

 

WOW, you must have special ordered this truck and I bet you get a very good MPG. But can not use it for a truck setup like that and only use OD on the Interstates.
In short a 5.0L engine can not work with a 2.7?:1 rear end in OD. You need from a 3.31:1 to about a 3.55:1 and if you are going to pull stumps a 4.10:1.
Yes, I bet it does ping and shake.

 

So I gather what you're saying is - I am not able to utilize the engines "working " range because of the gearing. As I understand it and have experienced it - there is a lean idle misfire issue with the 5.0 which makes it essential to keep the engine RPM's up. When I went looking for a truck that year I did NOT want the EOD transmission because it had just been introduced into the trucks and there had been some problems with it in the cars. The dealer located this truck for me and I did'nt realize it had the gearing it had until after I had received it. My gas mileage, however, only averages around 13.5 with the high being 15-17 and the low being around 10. Thanks for the reply.

 

Yes I guess the MPG would not be that great with an engine that is lugging all the time. You would get about the best MPG with about a 3.31:1 and more power with a 3.55:1. Of course since you have a 4X4 if you change gearing you have to change both the front axle and back axle gears.
I am sorry that I do not know any other way to fix your problems.

 

Does your truck have a tachometer? If so-- what RPM are you turning at 60 MPH with the truck in overdrive?? I didnt know that you could get a 4x4 with 2.73 rear ratio. What size tires do you have--235/75 x 15??.

Check your VIN label in the driver's door jam--see if the axle code is "12"--that is the code for 2.73 axle ratio. I bet you have 3.08s--that code is "18' if the differential is open or H8 if the differential is limited slip.

If I was you--I would check the initial timing and also check that knock sensor and make sure that they are within spec. The initial timing should be 10 degrees --I believe .

Does using higher octane gas make any difference in the engines propensity to knock?

 

Thanks for the VIN/code info. I'll check it again, but I believe I remember that the original "window/order sticker " said it was a 2.73.The tire size is the stock 235-75=15. The truck is bone stock although I've added a Flowmaster muffler with dual outlets to the passenger side like the 351 and a relacement K&N air filter element. I've always run 90+ octane gas and have tried "booster" but it doesn't seem to make much difference. What resurrected this concern was that I drove the truck to New Orleans to pick up my daughter's old car - a Tempo. Pulling the car on a U-haul tow dolly was a challenge - manually shifting in and out of OD and having the trans fluid "adjusted" and shift additive added. I also added STP octane booster but nothing really helped. I have lived with this for almost 14 years but it really reared it's ugly head during this trip. Thanks for all the good info and maybe with input from you all and some bucks, I might be able to improve this situation. THX.

 

Well-- I have a 92 F150,5.0 regular cab that was custom ordered by the original owner. It has the 5 speed Mazda manual transmission and 4.10 limited slip in the rear differential and 4.09 open in the front differential. And I also have the 235/75 x 15 tires. And it was used to pull a 4000 pound horse trailer for the first 13 years of it's life.

I turn about 2250 RPM at 60 MPH and can get over 20 MPG at less than 60 MPH--if I drive it very carefully. I can get my 5.0 to ping only when driving around a city corner in 5th gear/overdrive. If I downshift to fourth--the pinging goes away. The 4.10s make it unnecessary to downshift out of overdrive unless the truck is going less than 10 miles per hour!! Who says that the 5.0 doesnt have enough torque at low speed??

 

I finally got around to checking my axle code on the F150 that I'm having vibration problems with. The label on the door post says it is a "19". What ratio is this ?