Hi, I'm finally having a 3.42 posi (found in '05) put in to replace the 2.73 highway gears -- any recommended vendors for an overdrive transmission (automatic, of course) for street/leisure use? I'd prefer one that will accept the original as a core. I don't think the three-speed w/ the new gears will be drivable otherwise. Anyone have experience with this? Thanks, Paolo
Running 3.42 gears and 28" tall tires isn't going to be unbearable. You'll likely be running between 3,000 and 3,500rpm when going 70-75mph. For an Electra I'd go straight to a 4L80e and associated controller, but a 700r4 or 2004r could be built to last if the engine is tame. A gear vendors on the back of your existing trans is also an option. OD Ratios 4L80e - .80 Gear Vendors - .80 700r4 - .70 2004r - .68 To make an OD trans survive behind a big block in a 5,000lb car is likely going to cost some dollars. I'd drive the car with the 3.42's and see if it's going to justify the cost. Payback on fuel mileage increase is going to be a long long time unless you're driving this car 10,000+ miles per year.
I'm Pretty sure you got the ratios a big off there buddy 2004r is .67 700r4/4l60/e is .70 4l80e is .75 and gv uniti should be about 2800 plus shipping ps. wouldnt use a 2004r or 700r4 past the 600hp mark
The GV overdrive is .78. I paid about 3000.00 for my GV, including installation and new drive shaft, but that was about 6 years ago. The GV and 4L80E are the best choices as they were made for heavy vehicles. The GV is rated for 1200 HP in stock form, and can be modified to take 2000 HP.
I like the 4L80E trans and agree it is a great choice for a heavy car with big power and sticky tires>\ If this is a street cruiser then just swap in a well built 2004R for about $1500 and you should be fine. All in all you stand little to gain by swapping from your current trans which is bulletproof and your highway gear. I would go with a 3.08 gear and leave the trans alone.... If I was to add an overdrive trans I would go with a 3.73 gear to take advantage of the overdrive gear. Unless you are like me and drive 110 MPH+, and if that is the case then keep your 2.73 gear and use a 2004R trans LOL.... Works for me.
I think I'd keep the 400 trans, 3.42 gears are going to spin the engine faster on the highway, but if you dont drive the highway much, its going to take a long time to recoup the 3 plus grand in gas savings for the swap to a 4 speed.
+1 on the 3.08 gear ... And if tou wanted more punch off the line put a 2.75 gearset in the th400 with a trishield perf. Torque converter
I still stand behind this post. I run 3.42 gears on a 26" small car tire, and driving in 4th gear (1:1) doesn't excessively wind the engine out, particularly by the standards of when these old engines were designed. The only hit is going to be in mpgs, and he'll possibly gain 3-5mpgs highway, 1-2 city, with the overdrive. Just a long payback period is all.
Thanks guys -- on your advice, I'll hold off for now and see how it drives w/ the new gears. I'd just had the the TH400 gone over and a new TC installed so it's solid. Paolo
Oh boy. Got the car into the shop for the swap and *surprise*, I had a 8.875" rear in the box! We were able to find a posi unit elsewhere so I will now have posi & highway gears, which isn't so bad after all. ou: So the 8.875" is for sale here: http://www.v8buick.com/showthread.p...carrier-ring-pinion-500&p=2036606#post2036606
Exactly, this is a great solution! But he already has the 3.42's, so that part seems set. I think I'd live with the TH400 as is for a while as is, see if you reallly need the extra gear. Ok, looks like problem solved! Alan still has the right idea. Glad you found the posi!!!
