Thoughts on the transmission

[padgett]

The Reatta transmission whether designated 440T4 or 4T60 all have a 3.33 final drive. The difference between the 2.97 88-90 and the 3.33 (91) seems to be in the sprockets used with the drive chain.

(Yes, Virginia, the Reatta has a chain drive between the torque converter output and the trans input shaft).

To get the 2.97 overall, the chain uses 37 and 33 tooth sprockets. Other ratios use different sprockets, 35/35 for the 3.33 ratio and 33/37 for a 3.73:1.

My question since I have never had one apart is "could the stock sprockets be swapped to get the 3.73:1 ?"

This would definatly impact MPG, but the effect off the line might be...interesting.

Does anyone know ?

[Guest Richard D]

I just found out that the tire shop installed 225/60/15 on the fronts and left the 215/65.15 on the rear. He did not mention it at the time but something looked and felt different. When I read the marking and saw what he did he made it as no big deal, at 60 MPH I am actually travling at 52 MPH. I said that was not accetable and GM has hundreds of engineers working on tire sizes and where did he go to school to learn wheel & tire dynamics. He finally agreeded to swap them out when he gets the new size tires in stock. Am I wrong, is having two different size tires on each axle a bad thing? I think so.

Richard

[padgett]

Not really as long as the same on both sides of the front axle. Would only make a difference in a 4x4. American roundy-round cars some times have different sizes on all four, is called "stagger". Of course they are rarely pointed in the direction they are travelling.

[Ronnie]

I wonder if it might cause improper operation of the ABS computer when sliding the tires during an emergency stop? Does it look at differences in wheel speed or just that fact that one wheel has stopped turning and the rest haven't?

Edited November 17, 2011 by Ronnie (see edit history)

[charlie1]

As Info my 89 Riviera has a 2:84 final drive axle ratio.

Tires are 205 70 15

Edited November 17, 2011 by CHAS1 (see edit history)

[padgett]

Pretty sure the ABS just uses a certain speed as a reset & looks to differences between the wheels and not actual speed.

As to the difference in diameter, a 215x65x15 is 26" and a 225x60x15 is 25.6". 799 revs per mile vs 813, less than 2% difference. I doubt that it is enough to trigger.

[Guest Richard D]

I have only put a few miles on them but there has been no strange ABS operation or warning lights. I still think it is the wrong way to do business.

[NCReatta]

I have only put a few miles on them but there has been no strange ABS operation or warning lights. I still think it is the wrong way to do business.

Without a doubt it's a terrible way to do business.. But know what was going through the guy's mind..

He didn't have four tires in the size you needed, so rather than loose the sale all together, he puts the wrong size on, then once you find out, he says he'll replace them. In the end, he still gets the sale.

Twisted, butI'm almost positive that's what he was thinking..:eek:

[Guest Recian]

back to what padgett was saying I think it's potentially possible and a 3.73 rear would help the reatta get up and go alot better in town but it would ultimately kill it's MPG on the hwy. The vehicle having a big V6 really doesnt need high gears like that or it'll be even harder to keep ffrom spinning wheels as it is now

[padgett]

Thing is that now the 225s are used tires. Guess I am having trouble understanding the issue, even when I have ordered odd sizes at Sam's, they have them in a couple of days. 215x65x15 is not an unusual size, I just walked in on Sunday and left with 4 new BFG touring TAs (sale ended on Tuesday and I do not care for Goodyears). Made in Woodburn, Indiana.

[Guest Richard D]

Well He may have made this sale but I or any of my family or friends will not patronize his shop any more. All he had to do was to be honest and order the correct size tires. He said he is getting Kuhmo which is the same brand my neighbor has on his Pacifica, came with the car in 2008 and still look good. He said he is happy with them. I am pretty sure they are made in China.

[Guest Mc_Reatta]

Kuhmo tires are Korean. Think you will be very happy with them. Some of them are rated very highly. You can check out the model you get on tire rack .com. I consider them to be an excellent value, though their cost seems to have risen quickly as their reputation spreads.

[Ronnie]

Kuhmo tires are Korean owned but they manufacture tires in China and Vietnam as well as Korea.

[Guest Mc_Reatta]

Just saw where china is manufacturing colored tires. They add dyes to bleached rubber to make many different shades.

So now you can color coordinate or contrast your tires to the body.

Guess it remains to be seen how the will perform and hold up to standard rubber ones.

http://english.ntdtv.com/ntdtv_en/science_technology/2011-11-18/color-tires-fresh-off-production-line.html

Kuhmo also makes tires that emit colored and scented smoke on burn outs for the drifter crowd!

Edited November 20, 2011 by Mc_Reatta (see edit history)