Quote:
Originally Posted by Onebean
My Turbo 350 is getting tired, and I'm trying to decide between rebuilding it, or swapping in an overdrive. The advantage of the overdrive is I can make the reared gears a bit deeper for in town fun. The trade off is a goofed up shift pattern on the column. My son's will never know what gear they are in or why it's not moving. Give me your thoughts and experiences.
Onebean
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Onebean, you'll find just about everyone has an opinion on O/D transmissions, some much stronger opinions than others. For every guy that swears this or that transmission is junk, ten more will swear it's the best thing since sliced bread.
700R4 is by far the most common swap, though, in bone stock form is not exactly the strongest trans on the planet. Certainly not TH400-level of strength and simplicity. As mentioned above, the TV cable will need to be precisely adjusted to avoid burning up your trans quickly, however, Bowtie Overdrives makes a very simple kit to do this at home (I think they call it TV-Made-EZ, or something like that). Bowtie Overdrives website is a wealth of info. Hundreds of threads on here about how to do the 700 swap if you go that route, as well as the 2004R route. Usually need crossmember relocation, d/s shortening, etc etc.
Since you mentioned the desire to go to a deeper gear for in town fun, well, it sounds like you are gonna run around doing burnouts, so keep this in mind when it comes to the strength of the trans you purchase. 700R4's can be built, and if you're gonna do burnouts, you're gonna need a beefed up one or it won't last. But it's a truck... burnouts?? Throw some wood in the back you'll look just as cool
ALSO - if you are wanting a deeper gear for such antics (I'm just kiddin ya, we've ALL done em, just less and less as we get older, wiser, and cheaper...)
keep in mind that if you do an O/D trans swap, you may not even NEED a deeper rear gear to get the off the line performance you seek. Most O/D trans have a notably deeper 1st gear than the TH350. 700R4, for example is 3.06 vs 2.52 in a TH350, so you're going to feel that off the line without touching your rear. So to speak.. Do you know what your current rear end ratio is? Best to know before you leap.
If you put in a 700R4 AND a deeper rear end, you'd likely find that your rpm is thru the roof in a smoky burnout without really moving your car forward much at all, it would be time to shift in about 2 seconds.
Now, you're REALLY not gonna like this, but... my preferred route is a GV over/underdrive. Keep everything stock, buy a shortened driveshaft from the local driveline shop (keep the original since it's EASY to revert to bone stock if you do this mod, and would be nice to not have to buy a new long d/s if you ever go backwards), and enjoy. It provides the overdrive you seek. It will NOT give you a deeper 1st though - it only adds a gear (if you choose to use it beyond just the overdrive function) between 1-2, 2-3, and overdrive from 3. So if your ultimate goal is burnouts, this wouldn't be the approach for you, other than the fact that it's bulletproof. If need a deeper gear today to do a burnout, you'd still need it with this thingy. But it is a primo piece of gear, not cheap either. Figure $3K new. About the price of a well built, stout, o/d trans...
Decisions, decisions.
If you just want to do burnouts, then get a deeper rear.
If you want better highway mileage/hauling, and bulletproof, get a GV o/u.
But, it sounds like you want the best of both worlds, so If you want both, then an O/D trans is probably your quickest route with the least number of changes from stock. Don't skimp on quality and I would not just stuff a junkyard 700R4 in it, it won't last long. 4L80 converted to standalone, or with it's own brain/controller, is a great option, but not inexpensive. 6Ls, bring your checkbook, and your wife's and kids' as well.
EDIT: Oh, btw, they do make replacement shift indicators that will show the O/D detent.