Mopar Muscle Association UK

Just been reading A and A transmissions website. They tested breakage of stock front drums at around 12,500 revs.

My unintended first gear burnout/launch saw me in first gear at just over 6,000 rpm before I shifted up.

Double that and I get 12,000 rpm , presumably if I'd not changed up and backed of whilst still in first gear instead, I could have had a nasty shock.

Yep, IF the sprag has broken you were very lucky.

It's worse than that, drum speed would go to engine revs x the first gear ratio, so that's 6000 x 2.45 = 14700 rpm. If you have broken the sprag you're lucky you've still got a floor in the car...

3.40 shows excessive first gear abuse due to open diff and street tyres. Not sure that damaged it..

Rebuild will include new governors from A and A to allow the trans to shift at 5,500 in D so I don't have to manual shift and risk any further silliness.

A&A are pretty pricey for parts. I always dealt with John Cope at CRT, easy to deal with and a good website, plus he's been specialising in Torqueflites for donkeys years. It is also worth noting that on the standard transmission, the low band is not applied when you select drive, it is only applied if you select manual low (1) or reverse.

That RPM speed Blue mentioned is astonishing.
I know you should not do burn outs in 1st and Drive but if like Miles you put the pedal to the floor, how do you avoid possible loss of legs? Is it a bad thing to shift at high rpm in gear 1?

MilesnMiles wrote:

3.40 shows excessive first gear abuse due to open diff and street tyres. Not sure that damaged it..

4.39 shows some excessive C4 abuse, still hanging in there Dunc

mad machs wrote:

MilesnMiles wrote:

3.40 shows excessive first gear abuse due to open diff and street tyres. Not sure that damaged it..

4.39 shows some excessive C4 abuse, still hanging in there Dunc

Nice one Mike. thats what we aim for,,

GJUK wrote:That RPM speed Blue mentioned is astonishing.
I know you should not do burn outs in 1st and Drive but if like Miles you put the pedal to the floor, how do you avoid possible loss of legs? Is it a bad thing to shift at high rpm in gear 1?

What you want to avoid is coming off the throttle hard in 1st, knock it into 2nd and then come off it. The sprag or to give it it's correct name, the overrunning clutch, is the 727's achilles heel.

So the 'judder' or no traction to sudden traction, can break it...
Still okay to set off in 1st full power and carry on up the gears, but not to boot it in 1st then at 5500rpm come off the power?



(hope you fix it soon Miles, take lots of photos!)

Yea that's pretty much it.

Jon, I didn't come off the power much, just let the revs drop to about 5,000'and shifted into second gear. I probably damaged the sprag on my last run. Burnt out and went past stage. With quite a few revs I knocked her into reverse, neutral and then first and did my last run.
Who knows?
No pics to see as it's just a standard trans removal; lots of bits you can't get to cos of headers, drop prop etc and get the trans out.
The difficult bit is lowering it safely without breaking bits of me whilst under the car

Interesting post with what and how you should treat those 727 and this is not a criticism of what's happened to Miles but having a clear understanding of shift and change times when using the boxes up and down the strip I know I've learnt a few things reading this topic. ( and yes I've also broken mine a few times too)
hope you get it sorted Miles

Rich

Here's something interesting, I'd often wondered how effective those TCS Kevlar trans shields really were, well here's the proof they ain't bulletproof! You can clearly see the damaged shield at the top, I guess it saved his leg but he still ended up with a broken foot.