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I'm going to swap out the T5 for one of these Tremecs. Right now I have the 3.27 rear end. The car was an Automatic formally. Question is what ratio would I want? I was also thinking of stepping up to a 3.42, so this would change the option again. I'm not to well versed in these type of calculations. Not to concerned about a high highway cruise speed. Don't really cruise much past 70 mph.
Stand down, found a calculator on Tremec. But I'm always open to opinions. Looking for more of a light to light type of thing but that has a nice highway cruise. Beyond 150 kph and we lose our cars up here so a high highway speed would be lost on me.
I agree, 3.73 will definitely be more fun. The first gear in that trans is pretty low and w 3.73 will be pretty snappy and rpm won't be bad at 70 and above. Just look into where the carrier cut off is for swapping gears in your current rears gear ratio. You may or may not need a new diff, just something to look into. I think the tkx also uses a different bell than a t5 so you may need to look into clutch release mechanisms.
I have 4.10 in mine w a t56 and its great. But I have a t56 w a higher first(2.66) and sixth(0.63). 3.73 w the ratios your looking at I bet would be pretty perfect. I'm sure a 350 tpi would pull the 342 well if your concerned. Let us know what you find.
I have 4.10 in mine w a t56 and its great. But I have a t56 w a higher first(2.66) and sixth(0.63). 3.73 w the ratios your looking at I bet would be pretty perfect. I'm sure a 350 tpi would pull the 342 well if your concerned. Let us know what you find.
Hawks has 3.70 that looks like it'll fit the Borg Warner 9 bolt. I don't want to get into replacing the entire differential. 3.73 to 3.70 looks like it makes very little difference. Mind you I just started looking so I imagine there's a 3.73 that will fit. The car is fun right now with the 3.27, T5 and recent engine mods. I'd imagine it'd be quite a demon with the 3.70 or 3.73. Seems it'll be around 200 to 300 RPM more at 70 MPH.
Yeah, 0.03 will make no difference. The gear swap will be most noticeable in the lower gears and make the trans feel a little tighter as far as gear spacing (tkx is a little wide) The lower gears will also be easier on your clutch. Maybe a little harder on the tires!
For your 1987 3.27 9-bolt, upgrades are 3.45 and 3.70. 3.70 was a factory offering in 1985 and 1986 only and was the 9-bolt's equivalent to the 10-bolt's 3.73. IROC/Z28 HO cars got 3.73 10-bolts, and Trans Am HO cars got 3.70 9-bolts. If you had 3.45, then I'd say leave it alone, but since you want to upgrade from 3.27, then definitely go all the way with 3.70.
Seems like an aftermarket manufacturer did offer a 3.73 for a 9-bolt at one time, but I haven't heard of it for many years. Not really much point anyway, since 3.70 is still available.
I believe that same manufacturer also offered a 4-something gear for the 9-bolt, like, 4.10 or 4.11. But, again, I have no idea if it still exists. A search of the internet would probably produce some info.
Stock gears back then in that range were 3.70 (37/10). Not sure you can still buy those. Peeps complain nowadays about they can "only" get 3.73 (41/11). So OK yeah whatever... yeah, arguably, a pinion with fewer teeth (let's say, 10) is "stronger" than one with more (and therefore slightly smaller) teeth like, say, 11... OK yeah whatever. You go girl.
I've heard there's 4.xx gears available for the 9-bolt butt never seen em. All the same I can't begin to doubt that they exist. For better or worse. Butt that's OK, if you can get em, more power to ya.
Me, personally, I'd rather have a favorable ratio, made in a facility that isn't the "low cost" provider, set up properly. I'd like for em to be reliable, durable, QUIET, and ... such that people (especially those of my preferred complementary sex) wouldn't get in my car and be all fearful about "what's that weird noyyyyzzzzze". Because, at some level, just being comfortable and reassuring and "normal", is better than some arbitrary "my geeeeerzzz are stronger than your geeeerrrrzzz". Now if this is a RACE ONLY deeeeeeel, where nobody but you has to endure it, that's one thing; butt if it's a street car, that's a WHOLE OTHER concern. At which point, "all the fast cars" kinda has to take a "back seat" to what you're REALLY trying to obtain. (no pun intended, butt one given anyway)
Stock gears back then in that range were 3.70 (37/10). Not sure you can still buy those. Peeps complain nowadays about they can "only" get 3.73 (41/11). So OK yeah whatever... yeah, arguably, a pinion with fewer teeth (let's say, 10) is "stronger" than one with more (and therefore slightly smaller) teeth like, say, 11... OK yeah whatever. You go girl.
I've heard there's 4.xx gears available for the 9-bolt butt never seen em. All the same I can't begin to doubt that they exist. For better or worse. Butt that's OK, if you can get em, more power to ya.
Me, personally, I'd rather have a favorable ratio, made in a facility that isn't the "low cost" provider, set up properly. I'd like for em to be reliable, durable, QUIET, and ... such that people (especially those of my preferred complementary sex) wouldn't get in my car and be all fearful about "what's that weird noyyyyzzzzze". Because, at some level, just being comfortable and reassuring and "normal", is better than some arbitrary "my geeeeerzzz are stronger than your geeeerrrrzzz". Now if this is a RACE ONLY deeeeeeel, where nobody but you has to endure it, that's one thing; butt if it's a street car, that's a WHOLE OTHER concern. At which point, "all the fast cars" kinda has to take a "back seat" to what you're REALLY trying to obtain. (no pun intended, butt one given anyway)
This should be perfect. Motive makes good gears also. I've heard some complain they're a little loud but I wonder if that's setup related. Either way they're a good quality. IDK what setup kit you're gonna get. Try and stick w timken bearings, or more like, I'd try and not use KOYO bearings. I try not to bash companies but I've had issues w their bearings years ago and in my diffs I always try and go w an American bearings (god knows what's actually made here). My point is, put good stuff in w those gears and you'll only do the job once! I don't know anything about 9 bolt setups, maybe your stock bearings are reusable. I've never reused diff bearings but I know some people do.
This should be perfect. Motive makes good gears also. I've heard some complain they're a little loud but I wonder if that's setup related. Either way they're a good quality. IDK what setup kit you're gonna get. Try and stick w timken bearings, or more like, I'd try and not use KOYO bearings. I try not to bash companies but I've had issues w their bearings years ago and in my diffs I always try and go w an American bearings (god knows what's actually made here). My point is, put good stuff in w those gears and you'll only do the job once! I don't know anything about 9 bolt setups, maybe your stock bearings are reusable. I've never reused diff bearings but I know some people do.
I'm going to let a shop do this one. I don't want to get into a situation where I need hard to find tooling and end up grounded. I'd think I probably will need new cones as well.
Yes, almost certainly. Be aware that the new ones aren't exactly right for the older rears, they need to have some material shaved off the end to fit all the way down into the carrier.
I wouldn't have a problem with Koyo bearings, or any others made in North America, Europe, Japan, Taiwan, or Korea. I'd avoid any made in China, India, Thailand, Malaysia, Indonesia, etc. Anybody making bearings in a "low cost" country might be trying to shave cost in any number of other ways as well, I'd just as soon not take that risk.
I'd avoid any made in China, India, Thailand, Malaysia, Indonesia, etc. Anybody making bearings in a "low cost" country might be trying to shave cost in any number of other ways as well, I'd just as soon not take that risk.
Absolutely. I totally agree. It's splitting hairs in terms of upfront cost for the cheap ones compared to the cost of doing the job twice in short order when they fail and probably cause even more damage. Do these new cones need to be precision ground? As in brought to a machinist?
Not really. The deal is, they're a bit "taller" toward the inside, than the original ones were; so they won't go all the way in, and will bottom out in the older carrier. I'm not sure exactly how much needs to be knocked off but I think it's around .100 - .125". I don't think it's real critical as long as enough is taken off to allow them to seat fully. Pretty sure if you search the forum you can find more details on it. It's similar to what you have to do to used ones to "renew" them to the extent that it's possible.
Not really. The deal is, they're a bit "taller" toward the inside, than the original ones were; so they won't go all the way in, and will bottom out in the older carrier. I'm not sure exactly how much needs to be knocked off but I think it's around .100 - .125". I don't think it's real critical as long as enough is taken off to allow them to seat fully. Pretty sure if you search the forum you can find more details on it. It's similar to what you have to do to used ones to "renew" them to the extent that it's possible.
Perfect. Doesn't sound like it'll be to bad of a mod. Now that I said that.....
10-13-2023, 10:20 AM
never thought to go with that ratio. I'll check out that calculator and see what that will do for the highway range 
