20 replies to this topic

[Rob Burgoon]

Is there such thing as a pro transmission? How much power is there to be reclaimed from drag over the typical junkyard tranny running the same oil?

Vendors, sell me on a rebuilt tranny. They tend to die shortly after installation in my region.

[john mueller]

Rob;
From my vantage point miata transmission rebuilds don't have longevity... That being said I gave a local re-builder a shot and it's been great (solid for the first 4hrs of last yrs 25hr, the entire SoCal NASA season plus two classes and Nationals).

I have two gearboxes sitting here that I plan to take to him to rebuild... One will become my spare the other will need a good home.

[Jim Drago]

IMO transmission failures are 90+ % driver related.. I have been through a total of 2 rebuilt trans since 2004. The first, I missed a down shift pretty badly and sheared the teeth off third gear. The second happened last year, it just stuck in third with no issues before that happened. ( this failure was due to inadequate lubrication as we were trying fluids we should not have. ) My team mate goes through 2+ a year.. I lift the gas pedal, push clutch to floor, engage the gear, let the clutch out, back on gas, a little quicker than that, but I do all the steps.. I do not rest my hand on the shifter either. My team mate speed shifts. IMO if a transmission is rebuilt by one of the many qualified people doing them and all the parts that wear are replaced, they should all perform well. If they fail shortly after installation and was not a reassembly issue, it is a driver issue. We offer a 90 day warranty on ours, covers all except obvious abuse.

As far as drag... In terms of negative pulls on the dyno.. I have seen 1-3 hp drag differences in good boxes.. The used ones are inconsistent, some good, some not so good. That being said, I have never seen a used box better than a rebuilt box in terms of drag or performance. I haven't tested others rebuilt boxes, but obviously dyno ours all the time. Our negative numbers are always very close. within 1-1.5 hp. We see a larger difference in changing fluids than I have seen changing from one trans to another. We have seen some used units that are similar to rebuilt ones. I think the deciding factor for most is what you value your time at. If you do your own work and don't mind swapping a trans out, buy used. If you want a good trans that you can put in once and forget it , go rebuilt or new.

Jim

[Rob Burgoon]

Jim, tranny shipping to San Diego?

[davew]

IMO, What Jim said.

Between Jim and myself, we probably do 50% of the SM transmissions on this side of the country. A used box will NEVER shift like a fresh one. They are worn out at 40,000 miles.

Upshifting properly, like Jim describes, is part of the issue. When you down shift, you must brake, wait, wait, wait, downshift and turn. Early downshifts will break teeth.

I have never broken a trans while driving. I also have customers who go through 2 a year.

Dave

[Johnny D]

Barry H here at MR.com is one of our best in NorCal for trannies.
Lives by LS.
Hartzel Automotive Svc

510 California Ave, Sand City, California 93955
Tel: (831)3946002
J~

[Rob Burgoon]

Is there anything in the way of clever stuff going on inside of a rebuild? Or is it just newer parts work together better?

[MPR22]

'Jim Drago', on 18 Nov 2011 - 12:18 AM, said:

IMO transmission failures are 90+ % driver related.. I have been through a total of 2 rebuilt trans since 2004. The first, I missed a down shift pretty badly and sheared the teeth off third gear. The second happened last year, it just stuck in third with no issues before that happened. ( this failure was due to inadequate lubrication as we were trying fluids we should not have. ) My team mate goes through 2+ a year.. I lift the gas pedal, push clutch to floor, engage the gear, let the clutch out, back on gas, a little quicker than that, but I do all the steps.. I do not rest my hand on the shifter either. My team mate speed shifts. IMO if a transmission is rebuilt by one of the many qualified people doing them and all the parts that wear are replaced, they should all perform well. If they fail shortly after installation and was not a reassembly issue, it is a driver issue. We offer a 90 day warranty on ours, covers all except obvious abuse.

As far as drag... In terms of negative pulls on the dyno.. I have seen 1-3 hp drag differences in good boxes.. The used ones are inconsistent, some good, some not so good. That being said, I have never seen a used box better than a rebuilt box in terms of drag or performance. I haven't tested others rebuilt boxes, but obviously dyno ours all the time. Our negative numbers are always very close. within 1-1.5 hp. We see a larger difference in changing fluids than I have seen changing from one trans to another. We have seen some used units that are similar to rebuilt ones. I think the deciding factor for most is what you value your time at. If you do your own work and don't mind swapping a trans out, buy used. If you want a good trans that you can put in once and forget it , go rebuilt or new.

Jim

Jim,

So what fluids give the least HP loss

[James York]

'MPR22', on 18 Nov 2011 - 01:01 AM, said:

Jim,

So what fluids give the least HP loss

Customer secret.... No soup for you!

[john mueller]

'MPR22', on 18 Nov 2011 - 01:01 AM, said:

Jim,

So what fluids give the least HP loss

I've been using WD40

[FTodaro]

Last winter I tore into rebuilding my transmission because the reverse gear had a broken synco. I had never rebuilt one before. got everything I could read on the topic and bough the "MX-5 Miata 1.8 enthusiast manual", it had a step by step approach. Talked Karl Zimmerman into lending me his tools and rebuilt the sucker my self. I raced it all season hard, and never had an issue.

I agree with Jim and Dave, if your patient and good with heal toe should have no issues. I don't bore shift or power shift. I push the shifter with the palm of my hand between 3/4. If you grab it like bowling ball and push it into the gate you will miss a gear.

On to your question about Pro tranny, well I am no pro, but the gears are held into place by shims along the way. there is a tolerance that has to be followed. I did not do this but I could see someone shiming to the lower end of the range to fee it up some but other than that and making sure that you have good parts and bearing, I am not sure you can do much more.

On fluid, I find Crisco Oil works well after deep frying some light french fries.

[Adax]

I agree, I've rebuilt 4 now and maybe I'm missing something but there's not a lot you can legally do in there to decrease drag. I don't think looser selective spacer items will free up much but they will probably make sifting worse. I guess you could "forget" the spring on the 5/R shift rod that keeps a little pressure on the reverse syncro (probably why every one I've been in is worn out), but that's not technically legal. You can tell a huge difference in sifting with new parts though, and are probably less likely to mess-up a shift and damage something.

[LarryKing]

Micro coatings are just a myth, aren't they?

[davew]

I experimented with coating and REM about 10 years ago. Do not waste the money.

REMing takes the high spots off the gear surface. 100,000 miles of driving does the same thing. REM just makes the sides smooth. The gear surface is already smooth. If the gears where new, it would make a difference.

The ones we did the coating on had nothing but problems. The coating seemed to jam up the syncros. I eneded up taking them all apart and polishing the coating off the syncro surfaces and installing new syncros.

Plus it is not legal

Dave

[LarryKing]

Hmmmmmmmmmmm

[Clayton L]

What about cryo-ing the gears? Is that legal?

[Jim Drago]

'Clayton L', on 18 Nov 2011 - 4:34 PM, said:

What about cryo-ing the gears? Is that legal?

Legal? no...
detachable? no...

Also a waste of time IMO

[Mark]

Until the last year I was a junkyard transmission guy. If I found a decent one I never had any issues with them. I guess I'm pretty easy on the trans or maybe just lucky as I've never had one fail on me and I thought they all shifted just fine. For this last build I put in a 'pro' transmission. Big difference. I've never had a car that shifts so nicely. I doubt there is much if any performance difference but with the more positive shifting I'm much less prone to miss a shift and zing a very expensive motor into oblivion. The trans is basically a 1000.00 motor insurance policy in my case. Would I do it again? You bet.

Mark
www.ironcanyonmotorsports.com

[Blake Thompson]

+1 for dave's tranny. Probably a .5s/lap difference for me over a junkyard trans. Since I had so many of them it was way easier to just toss another one in a few times a season but Dave's rebuid got me through two seasons nicely.

.5 in drag? no, .5 in nice tight shifts where they belong and not missing gears due to sloppy forks and worn syncros.

[Blake Thompson]

'Rob Burgoon', on 18 Nov 2011 - 01:00 AM, said:

Is there anything in the way of clever stuff going on inside of a rebuild? Or is it just newer parts work together better?

careful, considerate construction always beats a robot. That's most of the magic in a fast motor too.