Awh man, blew another transmission

[Luke]

Well I think the point is it's flexy in the diff area, but not up by the actual gearset. Thats not to say the gearset is strong, just that failures there are simply related to the torque handling capacity of the gear, not to misalignment related to flexing of the case itself.

[Nate]

How do you shift a dog box? I know that you have to be very quick with the shifter but do you have to shift at a high rpm?

If you guys ever get a uprated gear set group buy together, I'm so in.

[TRAILINGTHROTTLE]

most of my experience with dogboxes is from formula fords and formula mazdas...they had less dog teeth on them than the typical rally or sedan roadrace box seems to have. on those boxes you could upshift however you felt like and didnt even need to touch the clutch. all that was important is that you didnt get lazy and stop moving the shifter before the gear was FULLY engauged...no syncros to help pull you in the rest of the way. on downshifts you needed the hell out of the clutch and as long as you could get in the neighborhood with your blip---snaped right into gear. the more dog teeth the stronger the setup(all other things being equal), but the more difficult to engage a gear(less opportunity for the dogs to fall in a gap).

[allessence]

Took the blown trans apart last night. 4th gear had a few half teeth left, but the cluster was completely toast. Not a tooth left on the gear.

This is the 2nd time in the last year I have had a syncro spring retainer/spring fail on 4th gear. completely wipes out the box. Argh.

I never used to see this kind of failure in earlier boxes1985-1990 after 1980 that had the bevelled cluster on 3rd gear. Seems almost crazy to find this in 4th all within a year in 2 different boxes.

So, Now I am in the testing phase for trans oils. Have spent a small fortune on different brands. Royal purple: Max gear 75w-90 11.00quart, 10w-30 motor oil 5.99 quart(after talking with tech support they said it had a high shear load and would still work and swore it had a high shear and load strenght.

BG syncroshift II. 12.75 quart. This is a 80W-90.

Will also get some Amsoil MT 75w-90, and some Redline MTL, and shockproof.

Buying a minimum of 7 quarts to change out the old (3quarts) and have a decent new oil fill the 2nd time around (another 3quarts with some to spare for top ups).

Currently am using the Royal purple 10w-30. Not impressed so far. Will follow up as time goes on.

As for stronger gears/cluster. I'd be up for something in the 1000-1500 range. Really can't afford anything more expensive unless it's a full on high HP box.

this last time around a couple of days before the incident the trans shifted a little hard into 2nd (thought it was the cold weather and the royal 75w-90) Once warmed up still a little notchy but not anything really different.

[allessence]

One other thing which I thought was unusual is the spring on 3rd gear syncro was also locked into the groove around the stamped spring retainer. I haven't tried to free it yet.

Wish I have a way to tell exactly what happened first. I mean besides big HP

[TRAILINGTHROTTLE]

cant tell enough in the pictures to determine, but is there any possibility that this gearbox was in 2 gears at the same time?

[allessence]

cant tell enough in the pictures to determine, but is there any possibility that this gearbox was in 2 gears at the same time?

No, I doubt it. I'm sure it was only one gear 4th.

What happened is I had just shifted from 3rd to 4th and started to generate large boost #'s (28lbs) and thats when it went kaboom. At that kind of torque it just knockes the teeth off like chicklets. especially with a 2.5mm wire spring between the gears. The spring hit the bearing shield and ripped it right out of the bearing and added to the mess.

[Raul]

Took the blown trans apart last night. 4th gear had a few half teeth left, but the cluster was completely toast. Not a tooth left on the gear.

This is the 2nd time in the last year I have had a syncro spring retainer/spring fail on 4th gear. completely wipes out the box. Argh.



]

Did you rebuild that tranny? Seems like you haven't placed spacers correctly. It is very critical, we are talking about 0.1mm tolerance. I don't know about oil realy, as long as it is not too thick it will work fine and not make your tranny fail. I run 75w synthetic red line in my box and I have been running my spg hard and it is still good. I never had this kind of tranny failure ever.

[TRAILINGTHROTTLE]

o.k., seems reasonable, just looking for a possible explanation for THAT type of damage(other than big HP), and ive seen it from being engaged in two gears at once.

[paulh]

ha! let me guess that was a 91+ box? the last failure i had looks like it was damn near identical to that one, even found the spring in similar shape, seemingly it had been crushed in between some gears. dont the 89-90 boxes have different synchros? i'm thinking the later synchro setup is junk, or they were lazy and put the boxes together poorly, cause the 89-90 trannys seem to hold up much better.

these are the pictures from my trans, looks like the pictures could be of the same trans if you didnt know any better!







mine failed on a 3-4 shift too, once it got on boost, poof...

Paul

[allessence]

Paul, this looks like the same failure big time.

What are you running for oil in the trans?

[Raul]

+91 transmissions have different gear pich than the rest. It could be that factor too.

[paulh]

i honestly dont recall, it happened a few years ago at this point, it may have had redline shockproof in it (terrible terrible shift quality) or perhaps honda MTL. i'm not too sure it was fluid related though, looks more like that spring went, and caused trouble throughout the box.

Paul

[Nate]

Did you rebuild that tranny? Seems like you haven't placed spacers correctly. It is very critical, we are talking about 0.1mm tolerance.

The newer boxes have a scary tight tolerance. When I rebuilt mine I was .0005 over the tolerance. Close enough I would think.

[DeLorean]

haha, yep I have had the same failure 2X with the 91+ boxes. Oddly, the 89-90 ones I have run I have never had such a failure.