Don't know what it is but the ap2 tranny I swapped in really doesnt like to go backwards at all.
the first 6 gears are GREAT and smooth but backing up just makes the awful whining noise its both annoying, embarrassing and kinda scary that something might be busted. its also kinda hard to actually put it into reverse

anyone have any idea where to start? or did I just get a junked up AP2 tranny that someone was doing reverse burnouts with?

 

Does it sound kind of like a whining sound that gets higher as you go faster? Ive been told reverse gears are different from regular gears in that they arent as "smooth" on the gears

 

Reverse gears are normally straight cut. This makes for a noisier gear (but it is cheaper to make and easier to engage/disengage). Forward gears (and your ring and pinion) are helical cut to reduce noise.

OP, if the noise you are hearing is a "whine" that gets louder/higher with wheel speed, then it is probably normal reverse gear noise.

 

In the s2k gear box all gears are helical (in any way: not straight) cut, even reverse.
Reverse also has a synchro.
There is an idler gear between the 2 revesre gears, to get reverse
Maybe that small gear has issues?

You could change trans oil and look for debris.
Allthought the trans has an internal magnet.

The noise is not, as in: for sure not, coming from the diff?
Or the rear in general?
Axles?

Just asking.

Btw.. selecting a gear does not mean you actually get gear wheels to engage.
You select a gear by sliding a synchro & hub on a splined shaft, the hub locks the freewheeling gearwheel to the shaft, if you know what I mean.
The cut of the gear wheel has no relation to shifting, just noise and what forces are generated by power transfer.
Helical gears (not straight cut gears) also generate axial forces, straight cut gears do not.
Most common gearboxes today - probably all but the S2k gearbox - are constant mesh, helical cut gear (exept reverse ) gearboxes.

The ring & pinion are Hypoid gears (it could be Helical's brother, I donno)
Maybe for noise, but mainly to generate axial forces by rotation.
And, you can put the pinion well below ring centre to create ground clearance.
And that's why you need a single SAE 90 weight... ok ok I'll stop!

 

I understand the normal gear whine from straight cut gears having no axial load and a smaller contact patch, it's like normal reverse whine cranked up to 11 on a 0-10 scale

Fresh Honda mtf in there 300 miles on it now. It's warm out around 70* so ideal temps when warmed up.

 

I know it is 10 years from last post (lol) but I also have same type of issue and was wondering what you may have found out about your reverse issue. Did you ever figure out the issue?

 

OP probably sold the car and now lives life in a constant state of regret.

Probably best to post your car's symptoms independently. 10 years have gone by...we have better access to high def video and sound to help diagnose this kinda stuff. The better you explain the issue, the better the answer.

 

I think I recall a post years ago by SpitfireS on his car winding up in a canal ditch somewhere in Holland where he lives.