Rear end hits hard going into 2nd gear

[Mike_HKmtrsprts]

I have a 94' f150 the transmission was rebuilt about 6k ago and had a mild shift kit put in it which I can feel, but some times when I floor the truck or at about half throttle as soon as thr truck goes into 2nd gear only!!,it hits hits really hard today I left out of my house track with my foot to the floor and as soon as the truck when staraight and shifted to 2nd gear it blew out the u-joint holder on the 3rd member,the end of the drive shaft and ruined the slip yoke,it has an auburn locker in it the drive shaftplace said to change the fluid or maybe add some of the addative that stuff for locker rear ends?? and answers would help cuz I dont want to spend $250 in a month or two and its not the transmission cuz the rest of the time it shifts like a dream thanks......Mike

 

[fnkrngr]

its the transmission if it only does it in 2nd gear

 

[Mike_HKmtrsprts]

I would say yes to the transmission but it really only hits hard after I hard made a turn like out of a housing track or parking lot once your driving down the road it shifts perfect its like the rearend it trying to lock up into a full spool? my work vans limited slip turned into a full spool one day so I took it to the dealership and they drained the fluid and re filled it and its worked perfect ever since the said it didnt have enough of that special addative that allows the clutch packs to slip during shift points???......Mike

 

[kjmiller1]

Do you think its possible its the brakes? I have a 93 150 and have had a bunch of problems with my rear brakes. If its your brakes, it may be the rear abs doing funky things, or more likely the pads catching on the drums making them bind. I read on a ford truck forum about a lot of guys with our style 150s having their pads catching and locking up or "hitting" really hard. Their solution was to switch from metallic pads to organic. Mine never caught going more than 15, but the firm shift might shift the pads just wrong. Slower speeds it locked up, usually out of turns but going faster it hit. So if you haven't done your rear brakes in awhile you might want to give this a try, go with the cheaper non-metallic pads, file the lips of the pads at an angle where they would grab the drum, and make sure your drums are still in spec.

 

[Dillon]

Is it from shifting from first to second or from third to second? I'd flush out the rear diff and install some synthetic gear lube from Mobil One and see if it helps. If it is from first to second its only doing it in second mostly likely cuz you usually aren't shifting into third gear in hard street turns.

Has it always done this or is it something new? Change the diff lube for sure, if its that simple and you spend money later you are gonna be pissed.

 

[Ryno]

Mike-

If what I am reading is right, you need a beefier u joint. When you hit the gas around a corner with a locker in the rear, when the truck goes straight, it's gonna lock the rear. When you're only going from 1-2, you have a TON of torque going back there, and something is gonna give. Your transmission is built, so the weakest link (u joint) went. Spicer makes the best I have heard of, Chrisman, Dynagear, or Currie could sell you a solid joint that is bulletproof I'm sure. If the joint is more than $20, I'd be shocked.

Ryno

 

[UndercoverFab]

if by auburn locker your really do mean a locker and not a posi your trucks always gonna be like that, when you go around a turn it disengages and acts like an open rear when you straighten out the locker engages and basically locks the axles together, your noticing it between first and second more then second to third because the change in ratios is steeper between first to second then second to third, the ujoints and yoke take most of the absue when it engages and disengages, step up to a bigger shaft with 1350 joints or at the minimum get a quality u joint like Ryno said.

 

[Mike_HKmtrsprts]

the problem is acually in the trans I had Brian from Transwerks look at and test drive it I believe he called it a slide bang? Im just waiting for him to finish 2 trucks and mine goes into to see if he can fix it via the valve body, he said the trans fluid smelled fine look red and didnt have clutch particles floating in it so he thinks some bumb a$$ might have put the shift kit in wrong, well see.....Mike oh yeah ryno fords come stock with spicer u-joints and I told the driveline shop I wanted the good spicers put in and thats what i got....

 

[fnkrngr]

Hmmmm i seem to recall saying that earlier in the post J/K