Pinion Failure-Why?, Gears in disarray Options

[brant]

we have actually now switched from the mobil 1 75-90W

over to the Mobil 1, 140W
(available at semi truck supply shops in a 5 gallon drum)

anybody need 4 gallons of left over 75-90W in my garage? ha...

brant

[Brad Roberts]

We run nothing but Mobil1 in all the late model tranny's. I run Swepco in STREET cars. I'm up to 4 tranny's now that dont shift when they have 20miles of street driving on them. Common denom: Redline Synth in all of them for a short period of time.


KenH,

I'm betting this was a stock tranny that was never checked. You would be amazed at how few people actually have the proper tools to set pre-load on the diff. I can only think of 10+ shops across the USA that have a decent selection of pinion shims.


B

[groot]

I certainly didn't check the pinion depth..... but I also didn't change any parts that effect the pinion/ring mating. I only changed out 3rd, 4th and 5th gears for shorter ratios... no bearing changes. I was anticipating going to a Hewland eventually.

Seperate question, that I'm sure everybody already knows but me. Does a 915 bolt up to a 4 cylinder? Can I move the ring over to the correct side? Is it a feasible solution?

[Brad Roberts]

You want a 76 912E tranny. It is a direct bolt up 915 tranny with a T4 clutch input splines.

Yes. You can easily flip the diff and run a WEVO shift solution if you choose. You can also go to straight cut gears (dog ring box)

It would be cheaper/easier for you to switch to a MK/Hewland solution.

Unless you measured the gears coming out and the gears going in and KNOW for sure that they are identical.. you should have checked pinion depth. Not all gears are created equal. You see/hear of us talking about switching out gears, but no one ever talks about the consequences.

We ran with 3 boxes as I mentioned above. All 3 had LSD's. One was partially disassembled until we needed it for a race. All the gears where pre measured so we wouldnt mix gears sets against the "pre-set" R+P of the 3rd tranny.

You are doing fine with what you have. Slap another tranny in it like you mentioned and go on your way (IMG:style_emoticons/default/clap56.gif)


B

[groot]

I hear you Brad. Considering the cost of the "rebuild" 2 seasons ain't too bad. I knew I was cutting corners when I did it. I can't help it, I'm cheap.

Another question on the 915... Ignoring the clutch spines, since I'm fitting a new 7.25" clutch and pressure plate tilton and they're relatively cheap, will other 915 boxes bolt up to the 4 cylinder, or is it just the 912 box?

Ironinally the 915 2nd, 3rd, and 4th line up quite well with the 3, 4 and 5 ratios I've been running. I'm just thinking of building a more solid back-up solution and then wait on the Hewland for a bit longer.

[Brad Roberts]

Yes. You can actually bolt a new 996/997 GT3 tranny to your 914 engine. It weighs more than the 914 engine, but you could.

Yes. All the 915's are direct bolt up. The 915 pilot bearing is the same bearing used in the 914 flywheel.

The big difference: 914 uses a push clutch and the 915 uses a pull clutch. This is VERY easy to get around.


B

[Brett W]

I have never seen the tool to setup ring and pinion, could it be done with a dial indicator, kinda like checking the backlash on a cam gear or intermediate shaft gear?

[Bill Smith]

how do you set the preload on the diff and how much?

[KenH]

Set pre-load.

Remove the o-ring gasket from the cover. Set the cover on the bearing. Using 4 bolts on opposite sides of the cover tighten them equally until there is a "even" gap all the way around the cover and the case. Note - exert as little pressure on the cover as possible. Measure the gap. Look for .008-.01" gap. To change the gap the wheel bearing has to be removed and shims are placed under the bearing. Shims are available from the dealer.

[john rogers]

At several of the vintage races I have seen some of the old Can-Am cars barely make it through a weekend without R&P failure. They all looked just like yours. I have seen several of the HSR/HSR-West R&Ps that failed and they were all the same too. Most of the 2L class 911s and 914s run a cooler and pump system to get cooled oil on the R&P as I started to do a few years ago and so far I have had no failures. Most setups I have seen have a nozzle over the R&P and another over the gear cluster. A handy addition is the temp plug adapter that Jim Patrick sells that replaces the speedo plug and lets you use a VDO gauge to keep an eye on the temps.