Hey guys I have another ZF5 question for all of you. I bought a used trans from a guy and swapped it into my truck about a year ago and for the first few months the trans was acting fine and shifting smooth through every gear. All of the sudden 1st gear started to grind real bad which did not bother me to much because I start in 2nd anyway. About two/three months later R began grinding/slamming into gear unless i shifted to a gear with good syncros then down into second. Of course not long after R went 2nd started to grind very bad unless I went to a good gear first to reset the syncros and then into 2nd. It is not even possible to drive the truck shifting from 1st to 2nd while driving without it grinding VERY bad, and it is especially annoying when im towing my boat. I have kind of learned a way to avoid grinding by shifting into 3rd first and then into 2nd to start off and then just going through the normal pattern while driving with no grinding, however it is very annoying as everytime i go to shift into 2nd when going to make a turn, I have to be going less than 5mph or it will grind. I have changed the fluid and played with adjusting the clutch pedal and they both did noting. Long story short, my 1st 2nd and R syncros are just shot I think. I am in South Florida and do not know of or trust any tranny shops around the area, so I am looking for someone that sells a good rebuilt ZF5 that can eventually hold up to around 450/500 hp. I have heard good things about high impact and midwest, but I came across this website which I think is through Xtreme Performance https://spprecision.com/products/zf-...sion-sale.html. Theirs is listed for $1295 with a $700 core charge. I know you get what you pay for, so if you guys think it is better to go with High Impact or Midwest, I am fine with paying the extra cash. Anyway let me know what you guys think about the website a attached above. Hope everyone is staying safe during all this Bull $...

Thank You,
Christian

 

Before you go to far, check you pedal box bushings. If they are ok check your your throw out bearing arm and see if it has proper amount of travel. This sounds a lot like the pedal box.

 

I have already checked the pedal box bushings, when I did the swap I bought a brand new pedal assem

 

Also if it was something with the pedal box wouldn’t it not shift smooth into 3rd 4th or 5th? Because if I push the clutch in and go straight to 3rd 4th or 5th, it doesn’t grind at all and shifts right into gear

 

I rebuilt mine. Here is what I know -

Shifting into 1st or Rev only can happen fully stopped or creeping around 1-3mph area. I guess you might be able to rev match to do at a slightly faster speed.

You cannot make a fast 1-2 upshift. Gearset weighs too much for that and all have a single cone syncro ring. It will grind every time treating it like some triple cone syncro trans in a car.

1/2 are on one slider. 3/4 are on one slider. 5/R are on one slider.

Do you know how to rev match on upshifts? If you still grind, you probably have internal damage. Only place I would buy a unit from would be Midwest Trans.

 

Yes I have tried rev matching going from 1-2. When I finished the swap it shifted perfect from 1-2 and through all the other gears. I can rev match 2-3 and 3-4 then 4-5 but it will grind if I try doing it from 1-2. And that’s what I have heard is to go with Midwest.

 

But as I said if I am at a stop and I push the clutch in and go to 1st it will grind/slam into gear. Same thing happens if I stopped and push the clutch in and go straight to 2nd or R. However, if I push the clutch in and shift up to 3rd and then into 1st, 2nd or R it will not grind. If that makes sense

 

Let me know if you can view these video. This is clutch in and straight to 1st. Clutch in and straight to 2nd is worse and it does the same for R

 

You sure the clutch is fully disengaged?

My 5/R slider had ground off dogs on R side. Bet you have same issue. Try clutch in, hit 5, keep clutch in, then pop into R. That makes the application of R much easier. May help some if slider is junk. You may have to replace that gear on main shaft too, depends on extent of damage.

1/2 should drop in with pedal down and at dead stop.

Disconnect driveshaft at trans and get a pal to depress clutch in neutral w that inspection cover off. I recall being able to see the clutch disc. You should be able to tell if fully released. You could also put it in gear and see if yolk spins still.

Did you measure slave cyl throw?

 

Also did you look at the master cyl rod to see if the eye is elongated or bushing broke missing?

 

So I was trying to rev match 1st to 2nd yesterday and it just grinds terribly, I can rev match 2-3, 3-4, 4-5 without using the clutch no problem at all. I’m assuming this probably means my synchros are probably toast for 1st, 2nd and R. Would you guys suggest taking mine to be rebuilt or order a reman tranny. Talked to high impact and it is $1700 with a $500 core charge and they said they can ship to me in Florida with free shipping, tranny will arrive in 5-7 business days. Has anyone on here heard good things about high impact? And also I need something that can handle around 450/500 hp eventually.

 

I would not worry about the power capacity on the trans, once you see inside one you will see what I mean. It is about 175lbs dry...and the case is aluminum. 450-500rwhp single disc will be like my SB OFE unit.

Is $1700 including any damaged parts replaced or do they just exchange? Make sure you replace yours with same model, especially if you have an S5-47. The -47 is geared better. I have never heard of High Impact, sorry.

I really doubt you have a bad reverse syncro, you probably have a chewed up gear and slider. Mine was like that.