Bushy

Well, for me that is a loaded question.<br>Let me say up front, I have paid for my system, in full, no sponsorship, no strings attached.<br>Again fluid coupling is our cross to carry....<br>In my opinion, I'd go straight back to the same system if I drove it over a boulder tomorrow and wrecked it.<br><br>All I can tell you is my experience with it. I have not driven but ridden in a BD truck with their TC and tranny. It was respectable. <br>Still when it came time to write the check, it went to DTT. BTW, the usual &quot;buyers remorse&quot; that happens to people after a major purchase has yet to happen for me.... it is a sweet system, period.<br>Not to mention service and custom tuning. In fact they may well service the heck outta ya till you yell for mercy.<br><br>Bob.

furious70

I'd like a further explanation as to what fluid coupling vs. lockup is?

Bushy

furious70,<br><br>I honestly do NOT want to come across as a smart a$$. It's not my style, and others will confirm that I think.... also, I'm not a tranny specialist/builder or anything else, so here is my explanation of fluid coupling vs lockup.<br>My apologies if this is simplistic...<br><br>Picture a large metal dougnut (torque convertor). The center of the doughnut facing the engine has an inlet to connect the crankshaft of the engine, and the rear of the doughnut has another outlet that the tranny connects to.<br>The torque convertor is basically two large fans. The only connection between the two fans, is transmission fluid. The engine turns it's 'fan', which in turns starts the trans oil moving. As that speeds up, the oil causes the opposite 'fan' to start turning. When this happens, the transmission shaft begins to turn and power starts to make it's way thru the tranny.<br>I'm leaving out a number of &quot;parts/components&quot; but this is the basics.<br>Now the &quot;efficiency&quot; of the two &quot;fans&quot; result in more/less of the power being transfered to the tranny. The tranny does the shifting and decision making in terms of what gear, when, etc.<br>In fact these fans can mulitiply the power the engine is providing a fair bit.<br>On our A518's there is no other component involved in the transfer of engine power, to the transmission and subsequently the rear wheels.<br><br>On lock-up systems, they still have the &quot;fans&quot;, they still mulitply/transfer the engine power to the tranny, BUT.... there is actually a clutch disk(s) in the torque convertor.<br>The fans do their thing in each gear, but at predetermined times/rpm's/speeds, the 'clutch' disk(s) are forced forward, against the inside face of the torque convertor. At this point, you are said to be in &quot;lock-up&quot;. Since it really resembles a clutch system like standard trannies use, it is the most efficient method of connecting the engine to tranny short of having a traditional standard transmission.<br>As you go thru the gears, the lock-up system engages/disengages in carefull timing to provide smooth efficient power transfer. It also results in less heat generation, and better &quot;pull&quot; over all.<br>The first gen trucks did not use the lock-up convertors, they came on the 94 model year and up.<br><br>Ok, so in our case the &quot;fluid coupling&quot; is what we need to be concerned with... that is unless you're going to go with a conversion which is a pretty respectable conversion.<br>So, what we want is the most efficient &quot;fluid coupling&quot; we can get, and still have responsiveness, drivablility etc.<br><br>In both cases the internal pressures of the transmission and, the efficiency of the torque convertor (generally measured as a percentage) will have a direct and significant impact on the &quot;positive/aggressive/firmness of each gear, each shift, and the &quot;pull&quot; you feel.<br><br>A rough guideline as to the stock convertor's efficiency is about 65-69% efficiency, partly due to it's operating range being designed for higher RPM gas engines.<br>The convertor I am using at present is rated a 89% efficiency. You can have 91% or 93% efficiency TC if you want them. The higher the efficiency the more HP/torque you'll need to make them work for you.<br>Lock-up TC's also have various efficiency ratings but they are designed to have each &quot;fluid coupling&quot; gear very close in efficiency to the lock-up points so the transition to lock-up is smooth, without the need to utilize &quot;slippage&quot; to make the shift smooth feeling.<br><br>Ok, that's the best I can do. PLEASE if I've missed something correct me so I can learn too guys......<br><br>BTW, there a number of aftermarket systems out there, and here are a few, beginning with my personal favourite...<br><br>DTT<br>TCI<br>BD<br>ATS<br>Goe rand (sp?)<br>Suncoast<br><br>bob.

furious70

Good discussion, but not what I was after lol. I know how convertors work, but I was under the impression that OEM 518's were all lockup. MP 'aftermarket' new 518's are not however. That's where my confusion as to the 518 not being a lockup is coming from.

Bushy

furious,<br><br>To the best of my knowledge none of the 1st gen auto's were a lock-up type system. That began in the 94 model year.<br><br>Weg,<br><br>Buying a better TC will certainly help, but you'll want to make some internal tranny upgrades too.. for example a tuned valve body and some other components like better quality seals etc to hang onto the extra pressure you'll need in the trans if you want it to hold higher HP.<br><br>Bob.

furious70

http://smrtrans.tripod.com/smrtransm...intro/id6.html<br><br><br>if you look there, they seem to be interchanging 518/618 and 46rh for their purposes, and calling them all lockups