Xtant3150c

iTrader: (10)

Yah it does depend on your spur gear size.

With the 93t spur I am running now the 56t pinion is the biggest I can go. It is to the point where the farthest I can move the pinion away from the spur is just far enough for good gear mesh. I am running a 54t pinion now which is best gearing for my car on our track and a little easier fit

karlo511

iTrader: (4)

for 64 pitch, i was able to fit a 90/51 (FDR 4.3) and had room to probably go up a couple of teeth.
reduce the spur size to get bigger pinions to fit.

Andysan

I am in dire need of help with my HPI Pr 4 please!

I have 2x Pro 4's, both running fine until about 2 months ago. When i race i hear a crunching from the front gearbox. The gears didn't look noticeably worn, but i replaced them anyhow. The same thing happeneed the next race.

Not having the time to spend on maintenance i switched to the spare car, but this is now doing the same thing. The sound is akin to human teeth rattling inside a box, but is only once every rotation of the wheels, particularly when the car leans around corners.

I am running one ways in both cars (i know they are bad for wear) and have so far replaced the one ways with new one ways and also regular diffs. I have replaced both gears numerous times with new ones (the revised type, meshed as instructed in the Hara ed manual), and also the bearings and layshaft. I have also altered the shimming but to no avail.

Tonight i rested the gears in another gearbox casing and turned them very slowly - they move fine up until an arbitrary point where they lock up very tight and wont budge, akin with he sound i hear once every turn. The lock appears random however, and i am not able to identify and mashed teeth on the gears or other parts that are misbehaving.

Could it be the gearbox casing sperhaps - i don't think it is because i have tried it on a different old casing that i had no problms with in the past.

I have made no changes to the cars - the only change is the introduction of rubber hosing at my track instead of plastic, but i don't think this is related (i don't crash allot).

Could somebody please ofer any help or advice to solve this problem, and general help in meshing my gears which i seem a bit crap at? I am only running a 27t, i don't think i should be getting these problems, especially to both cars at the same time.

Many thanks in advance!

TeckLancer

iTrader: (16)

i had the same problem. its the ball diffs. there not shimmed right. put some more shims so that the gears are closer. as u turn and throttle it there gears kinda seperate and thats the noise u hear.

shadow102

iTrader: (21)

how do the bearings look?

UltegraSTI

iTrader: (20)

hmm, interesting info indeed. for me to think that this car was hosed on using any BL combos in T/A b/c of that 2.4375 , glad to have been mistaken.

R

scootr117

Since the problem started then parts were changed I wouldn't say the shimming was the problem. I'd check the pinion gear shaft. During an impact the drive shaft tranfers force to these and can cause them to bend. This will show as a tight spot in the gears' backlash (mesh)

Andysan

Hi all,

Firstly, thanks for the help and support.

Unfortuantely, i still have this problem. To go into more detail, when the wheels rotate everything is fine. When there is some resistance, either through breaking or sharp cornering the girinding noise occurs, but it sounds like it is happening once per rotation, i.e. something is catching somewhere.

I though i nearly had it tonight when i noticed that the aloy disc behind the front gear was slightly bent, but replacing that hasn't worked either.

So far, i have replaced the following, some several times over:

Shims
Bevel/crown gears
Diff
All bearings in the front end (incl the front two corners)
Every part on the front two corners (i.e. bearings, hubs, cvd's etc...)
Chassis bottom plate
Grease (for gears)
Gearbox casings
Main centre shaft
Front propshaft
Motor & Pinion

Some of these things were daft, but I am running out of ideas now. I also have slightly more resistance in the front right wheel than the left, which may be related - I can't seem to pinpoint the problem there.

The problem only seems to get better when i put more shims behind the gear (to push the gears closer together as it sounds like they are slipping over one another at a particular point), but eventually i run out of space to fit the shims in.

I am running a front one way but have the same problem with a regular diff. I took the entire car aprt, re-greased everything and replaced any parts that looked haggered last weekend-still no joy. I could possibly understand it if these problems were a result of a hards weekends racing, but i am getting this when rolling the car down my drive!

If anyone has any ideas then i would really appreciate some help please - I reckon either i am doing something very wrong, or some parts i have have been manufactured incorrectly (big claim i know).

robk

iTrader: (22)

PRS makes 76 & 80t gears which will fit on a Pro4. You may not need such a wacky huge pinion that way.

pejota

iTrader: (12)

Andysan

Did you check the other moving parts of the drivetrain? For example, i had issues with outdrives and other axle parts randomly rubbing on screws when i bought my Pro 4 for VTA use.

I also had some issues with the front pivot blocks going askew after hitting a curb. You might wanna check the alignment of those as well.

Andysan

Hi - thanks for the reply,

I will check these out - could something that elementary be causing such trouble?

shadow102

iTrader: (21)

check your ball studs i know i installed ones that were too long on the inner parts of the camber links and they would occasionally rub on the outdrive

Andysan

Hi chaps,

Well I tried what i probably should have tried some time ago; I took the grabox off the problem car (including diff, 2x gears, layshaft, rollbar and camber plate) and swapped wit with my spare chassis. Oddly, this seems to have fixed the problem. Bear in mind that i have replaced each individual component that is anywhere near the gearbox.

With that considered, even stranger is that the test car appears to work OK. I can only assume that there were two parts somewhere that weren't getting on.

I race on a Friday night so will report back if all goes awry.

And thanks to all who made suggestions.

LORD SHADO

bad news i got banned from hpibaja furom.
i think their like x-ray site . talk no bad stuff about one of their racer. da da i cant believe how some furom have become so bad for talking freely.
any idea guys .

Isaac

iTrader: (5)

Anyone still using this car for racing?