GP1138 Posted October 19, 2004 Report Share Posted October 19, 2004 Ok, the auction for the Euro I just took delivery of made no mention of the fact that this car has the 125c 3-speed automatic transmission. I noticed this after I sat in the car and it had no Overdrive detent on the shift plate. I cursed very loudly when I saw that. Anyway, I'd like to know what kind of snafu this would be to take a 3.1/4T60 combo and drop that mothafucka in place of the 3.1/125c that is in there right now. Chris (White93Z34) and I have been discussing doing it at his place at some point before winter, and so far we've got questions out the ass. Would we have to change wiring harness? Computer? Halfshafts? Has anyone done this in the past? Is there a distinct advantage to upgrading to the 4T60, or would it be less hassle if I simply had the 125c rebuilt? Thanks for any info you can provide, intrepid purveyors of mechanickeral knoweledge! Quote Link to comment Share on other sites More sharing options...
TeeJay3800 Posted October 19, 2004 Report Share Posted October 19, 2004 The car will be faster with the 4T60 as the gearing is better. Mileage will also be better with the .70:1 over-drive. With only 3 speeds on the 125, each gear is even more of a compromise, so you'll see better performance with the 4T60. Quote Link to comment Share on other sites More sharing options...
GP1138 Posted October 19, 2004 Author Report Share Posted October 19, 2004 The car will be faster with the 4T60 as the gearing is better. Mileage will also be better with the .70:1 over-drive. With only 3 speeds on the 125, each gear is even more of a compromise, so you'll see better performance with the 4T60. I figured as much. I just wanted to make sure there wasn't some advantage I was missing. Quote Link to comment Share on other sites More sharing options...
TeeJay3800 Posted October 19, 2004 Report Share Posted October 19, 2004 The car will be faster with the 4T60 as the gearing is better. Mileage will also be better with the .70:1 over-drive. With only 3 speeds on the 125, each gear is even more of a compromise, so you'll see better performance with the 4T60. I figured as much. I just wanted to make sure there wasn't some advantage I was missing. I love pointing out the obvious. Quote Link to comment Share on other sites More sharing options...
maybe2fast Posted October 19, 2004 Report Share Posted October 19, 2004 I have drove a 3 speed they are soooo much slower! Quote Link to comment Share on other sites More sharing options...
Canada Posted October 19, 2004 Report Share Posted October 19, 2004 3.1L MPFI 125C...(4 cy and 2.8s received 3.10……I am not 100% sure if W bodies acquired 2.84s or not, I know the L chassis did.) 1st...2.84 2nd...1.60 3rd...1.00 FDR...2.84 RPM drops... 1-2...56% 2-3...62.5% 3.1L MPFI 4T60... 1st....2.921 2nd...1.568 3rd....1.000 4th....0.705 FDR...3.33 RPM drops... 1-2...53.6% 2-3...63.7% 3-4...70.5% The 4T60 has a deeper first gear, longer second gear, and the exact same third. This does mean the 1-2 shift is further spaced apart and the 2-3 is closer.......BUT you have a closer FDR to bring everything that much closer together. Don’t forget the advantages of an overdrive gear…. I like the addition of 4th gear for fuel economy....even with the deeper FDR, the overall ratio is taller......2.348 vs 2.84.....the motor is actually turning ~18% less rpm with the extra gear and deeper FDR. There is only about a 4-5 mpg advantage with 4th gear……….my roommate, who owns a 93 Beretta GT, and I went out to Colorado this summer with both our cars, I got to see the difference directly. I also view it as nice as to not see the tachometer north of 3k for several hours at a time. Then comes the matter of top speed.....I can pull to 5950 rpm in third gear with the Beretta (it only has 2.93 gears).....(I cannot shift into 4th as the VSS is disconnected at this point)..........if I could shift into 4th gear, that would drop me to 4200 rpm (just past peak torque) PLUS torque converter slip.....that should be enough to maintain my current speed......*maybe* accelerate a few more mph, but I doubt that. I need to play with CarTest. I view this swap the same as I do a 700R4 for Turbo 350 swap........its GOOD. As far as what has to happen to make the swap go.............I have no clue. Quote Link to comment Share on other sites More sharing options...
TeeJay3800 Posted October 20, 2004 Report Share Posted October 20, 2004 3.1L MPFI 4T60... 1st....2.921 2nd...1.568 3rd....1.000 4th....0.705 FDR...3.33 RPM drops... 1-2...53.6% 2-3...63.7% 3-4...70.5% Can you explain those percentages. I know for a fact that the RPM drops MORE going from 1st to 2nd, than it does going from 2nd to 3rd, but your percentages show a greater RPM drop from 2 to 3. Maybe I'm interpreting this wrong.... Quote Link to comment Share on other sites More sharing options...
White93z34 Posted October 20, 2004 Report Share Posted October 20, 2004 i'm thinking that you will probably need the engine bay harnas for the 3.1/4t60 unless the transmision plugs are identical for the 125c and 4t60 so i'd imagine you need the following - 4t60 - wiring harnas ?? - pcm, or at very least the memcal - halfshafts?? - PRNdD21 shift plate for the console theres probably more that i'm missing here. Quote Link to comment Share on other sites More sharing options...
mihela816 Posted October 20, 2004 Report Share Posted October 20, 2004 halfshafts are definitely different. Quote Link to comment Share on other sites More sharing options...
GP1138 Posted October 20, 2004 Author Report Share Posted October 20, 2004 halfshafts are definitely different. Alright, cool. Quote Link to comment Share on other sites More sharing options...
Canada Posted October 20, 2004 Report Share Posted October 20, 2004 Percent drop = Next Gear / Previous Gear. 1.568 / 2.291 = 53.6% You can then take that percentage and multiply it by the rpm you would shift at to get the rpm in the next gear at the same speed. This of course does NOT account for slippage in the torque converter. 53.6% * 6000 rpm = 3216 rpm. Quote Link to comment Share on other sites More sharing options...
rudefyet Posted October 20, 2004 Report Share Posted October 20, 2004 it's all vacuum controlled so the pcm may not be an issue Quote Link to comment Share on other sites More sharing options...
White93z34 Posted October 20, 2004 Report Share Posted October 20, 2004 it's all vacuum controlled so the pcm may not be an issue i was wondering that myself, the tranny may not have any wiring harnas for it, i'll find out soon enough. or one of you 3.1 /4t60 guys could always pull off your airbox and take pictures of the area where the engine meets the tranny, or tell us if there is any wiring for it. Quote Link to comment Share on other sites More sharing options...
GP1138 Posted October 20, 2004 Author Report Share Posted October 20, 2004 I remember about 6 wires up in the front of the tranny for the solenoid. I can't remember exactly what for, but I had a 4T60 at one point, lol. Quote Link to comment Share on other sites More sharing options...
White93z34 Posted October 20, 2004 Report Share Posted October 20, 2004 ok, now does your current 125c have those 6 wires? Quote Link to comment Share on other sites More sharing options...
rudefyet Posted October 20, 2004 Report Share Posted October 20, 2004 i counted 5 wires hooked to some sort of sensor... VSS..maybe? EDIT: just looked it up it's the VSS the VSS may differ between the 2 trannys so that may require you getting the memcal from a 3.1/4T60 car hopefully someone else can verify the differences Quote Link to comment Share on other sites More sharing options...
bartonmd Posted October 21, 2004 Report Share Posted October 21, 2004 I didn't know the luminas ever came with the 3.1L/3-spd combo (fairly rare?)... When did they stop that? Also, when did they go computer controlled tranny? Thanks, Mike Quote Link to comment Share on other sites More sharing options...
White93z34 Posted October 21, 2004 Report Share Posted October 21, 2004 yeah what johns got is a prety rare combo, a awful combo at that. i know all 3.4 cars got the 4t60-e i forget when they switched to that for 3.1 cars. Quote Link to comment Share on other sites More sharing options...
buckethead Posted October 21, 2004 Report Share Posted October 21, 2004 ugh, 3-speeds are horrible... The gearing in my old chrysler e-class's 3-speed meant that when i was going 75 on the highway, the engine was turning about 4400 rpm.... that couldn't have been good for longevity Quote Link to comment Share on other sites More sharing options...
GP1138 Posted October 21, 2004 Author Report Share Posted October 21, 2004 ugh, 3-speeds are horrible... The gearing in my old chrysler e-class's 3-speed meant that when i was going 75 on the highway, the engine was turning about 4400 rpm.... that couldn't have been good for longevity It has a TCC, so I turn about 2700 at 75 on the highway. It's not too bad. It's just not real fast accelerating. Quote Link to comment Share on other sites More sharing options...
cmo1234 Posted October 21, 2004 Report Share Posted October 21, 2004 It has a TCC, so I turn about 2700 at 75 on the highway. It's not too bad. It's just not real fast accelerating. lol, my VSS must be way off on my 3spd, when at highway speed like 55 and just keeping up with traffic my car registers 75 and 4k rpm. :shock: The VSS are different for a 3 and 4 spds. If you do the swap can i have first dibs on yours :?: i've had no luck finding one at j/yds and new they are like $80 Quote Link to comment Share on other sites More sharing options...
Tru2Chevy Posted October 22, 2004 Report Share Posted October 22, 2004 I didn't think the 3.1/125C combo was that rare....I have one, and I see them all the time. I can still get almost 400 miles out of a tank of gas (highway) with the lockup solenoid shot. I am debating whether to switch to a 4t60 or 282..... - Justin Quote Link to comment Share on other sites More sharing options...
KingArthur Posted October 24, 2004 Report Share Posted October 24, 2004 I bought a 92 Lumina Euro for the motor and tranny. On the dash it has the overdrive indicator but I noticed that when I pulled the shifter all the way to the lower gears it stop between 1 and 2. Then I notice that this car doesn't have a vaccum modulator on it. Does this indicate a 3 speed? Quote Link to comment Share on other sites More sharing options...
Baddflash Posted October 25, 2004 Report Share Posted October 25, 2004 My winter car has the 3-spd with the non-functional TC lockup. I have a spare 4t60 that I was considering swapping in but haven't decided if it's worth the effort, or if I should do another 5-spd swap. I know the vaccum line is run differently cause the port behind the TB is capped. Also the vent is different, the 3-spd uses the same one as the 5-spd the 4-spd is built onto the top of the trans. I've been told both the axles and wiring are different and possibly the MEMCAL but I haven't confirmed this yet. Good luck on the 4-spd swap (if you do) I know I wouldn't rebuild my 3-spd I would definately swap to something else. The only thing I like about the 3-spd is you're doing close to 50mph when you shift to 2nd. I actually raced both my Lumina's against each other before I swapped in the 5-spd. The 4-spd is quicker off the line but the 3-spd did some catching up when the 4spd made it's 1-2 shift. I think if I had done a tuneup on the 3spd it would have been a lot closer till it shifted to 2nd, then it would have been over. Atleast I didn't get beat by my own car, that would have sucked. Quote Link to comment Share on other sites More sharing options...
digitaloutsider Posted October 25, 2004 Report Share Posted October 25, 2004 You'll need the console shift lever assembly itself. The 125-c shift assembly is completely different, and obviously only has the shift positions for the 125-c. Quote Link to comment Share on other sites More sharing options...
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