Edmunds.com | Inside Line | Auto Observer Your Account | Help | Directory
You are here:
![[F]](http://a332.g.akamai.net/f/332/936/12h/www.edmunds.com/media/townhall/webxicons/site.gif){kind=small}
Forums
Sedans Cadillac STS/STS-V Cadillac STS/STS-V: Transmission
19 messages, Last post on Mar 14, 2007 at 2:35 PM
You are in the Cadillac STS/STS-V Forum. Your Hosts are pat & karens
I just purchased a 2003 Cadillac Seville STS with 28,000 miles on it. When i test drove it everything seemed to be okay, but after driving it about 200 miles I noticed that sometimes if I would accelerate fast off the line, the shift from 1st to 2nd gear would be so harsh that the tires would screech. I thought that maybe the transmission fluid was low, so I checked it and it was up to the right level and it wasn't a nice pink color. I went to pep boys and got a bottle of Lucus transmission slip/repair. I put half the bottle in the transmission and now it shifts like silk through every gear. I was amazed that half a bottle of liquid could make such a difference. I was just wondering if anyone else had a similar problem, or if anyone thinks that this is only a temporary fix??
|
|
|
|
|
Replying to: caddykid (Apr 13, 2006 7:15 pm)
|
|
|
Replying to: Mr_Shiftright (Apr 14, 2006 7:24 am) |
|
|
The overall ratio of the six speed is about 6:1, that is low gear (4.06:1) divided by high gear (0.67:1) gives and overall ratio of about 6:1. The 5 speed automatic is 3.42/.75 or around 4.5:1. With the same axle ratios, the six speed has a lower first gear and a higher overdrive which should give somewhat better highway fuel economy. If the gears in the transmission were equally spaced, then the 5 speed gears would be 1.46 apart (0.75; 1.10; 1.60; 2.34; 3.42). The 6 speeds gears would be 1.43 apart (0.67; 0.96; 1.38; 1.97; 2.83; 4.06). The basic problem is that to choose each gear would require a planetary gearset for each one. The actual transmissions have only 3 planetary gearsets, so some gears can be choosen, and the rest are combinations. The 6 speed has its top gears closer together than the 5 speed. The interesting thing about the 5 speed is that third gear is half way between low and high. While the 6 speed gearing on average is closer together than the 5 speed's, it is not much closer together (1.46 vs 1.43). The 6 speed seems to provide a somewhat lower first gear and a higher overdrive, so that somewhat better performance and fuel economy can both be expected. The EPA numbers for the Corvette do not seem to be that much different however.
|
|
|
Replying to: sls002 (May 22, 2006 7:30 am) The 6 speed, with the wider ratio spread, does indeed provide the opportunity for both enhanced acceleration in first and second gear as well as reduced RPM and therefore better fuel economy in the higher gears at cruise. The Corvette is an interesting case, in this respect. The replacement of the four speed with the six speed resulted in a loss of one MPG city and the gain of one MPG highway. The change was accompanied by a switch to the 2.56:1 final drive ratio. With the A4, it was 2.73 with option of 3.15. The A4 ratio spread was 4.37. And the 2006 Corvette’s new six speed has identical internal ratios to the 2007 STS’s. My take (after reading 2 sources) is that GM \ Chevy managed to deliver acceleration approx. equal to the C6 A4 with the 3.15 (G90 Performance ratio & sometimes on constraint) final drive while simultaneously achieving fuel mileage approx. equal to the C6 A4 with the 2.73 final drive. There is now only 1 final drive ratio for the automatic Corvette. Anyway – it appears that you and I are the only 2 posters on Edmunds that even care a little bit about any of the 2007 “stuff”. I guess that accounts for the last unsold inventory numbers I saw for 2006 STSs (well over 120 days) and the current apparent ability to buy one for well under invoice. - Ray Still ready for my 2007 test drive . .
|
|
|
Replying to: rayainsw (May 22, 2006 8:50 am) I think that GM's choice of low gear ratios on their six speeds (both RWD and FWD) are perhaps a bit too low. On the other hand, other production six speed automatics are using quite low first gear ratios, so I am sure that there is a reason. |
|
|
Replying to: rayainsw (May 22, 2006 8:50 am) Thanx again for the info
|
|
|
Replying to: quemfala (May 22, 2006 11:53 am) 2 - I have seen nothing to indicate significant upgrade(s) to the interior for 2007. But we'll see - in a couple of months. - Ray Also waiting . .
|
|
|
Replying to: rayainsw (May 22, 2006 12:15 pm) Playing around with my spreadsheet and the equations for planetary gearsets suggest that one could get from two planetary gears the following six ratios (4:1, 2.8:1, 1.9:1, 1.33:1, 1:1, 0.75:1). This would have the top three gears a bit closer together than the bottom three. Compared to the 5 speed, this would have a lower first gear, so the axle ratio could be changed from 3.42 to 3.08. This would give a lower overall ratio in the first 5 gears and still provide an overdrive ratio that is more fuel efficent. A 2.73:1 axle ratio would be somewhat mixed, some lower, some higher. I guess that my point is that I do not fully understand GM's choice of gears, or the sense in an overall ratio of the transmission to be 6:1. Based on the Covette's EPA results, I think the city mileage is not so good. The 2007 Saturn Aura is rated 18/27 with the 3.6 and six speed transmission, while the base Aura's 3.5 engine and 4 speed automatic are rated 20/30. This does not show that the six speed is resulting in better fuel economy. This may be a quirk in the EPA testing.
|
|
You are here:
Forums
Sedans Cadillac STS/STS-V Cadillac STS/STS-V: Transmission
New? Join Now!
Forum Tools
Search Forums
Browse by Vehicle
2010 Cadillac STS
2009 Cadillac STS-V
Browse by Board
Browse by Topic
Today's Chats
