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Manual Transmission Question

1K views 11 replies 5 participants last post by  mattt0305 
#1 ·
I was wanting other MT owners to chime in on this. Since I got my 2006 2.8L cts with the MT I noticed a lot of vibration coming trough the grearbox. You can actually watch the stick shake. Overall it shifts good and no gears pop out or anything. I'm just wondering if this is normal for this car because all the other manual I have driven do not have this vibration. I also get some vibration through the wheel at certain rpm's. I know the wheel shake is not from a poor alignment or tires because tires are new and I just got an alignment. Just let me know if anyone else is experiencing this too. Oh and I do have a catback exhaust if that will affect anything at all. It has a resonator so I get little cabin vibration from it.
 
#11 ·
I bought a 2006 Cadillac CTS with 112,000 miles, three years ago. It now has 142,000 miles. I love this car. It has the 3.6 liter engine, the six speed Aisin transmission and limited slip rear differential. It started clunking shortly after I bought it. I replaced the front differential bushing with the Creative Steel urethane bushing, which got rid of about half the clunking. Not long after the clunking started, it began to make a thumping noise while accelerating hard in first gear. This thumping gradually became worse over time.

About a month ago, something broke in the shift mechanism that caused me not to be able to get the car into reverse. SX54DX has a great post on CadillacForums.com on how to fix the shifter linkage. Search for his post. I used off-the-self bronze bushing instead of the urethane bushing SX54DX used. I put information about the bronze bushings on SX54DX’s thread (01NOV2014). Anyway, I got the car on my brother’s car hoist, and while I was showing him the problem with the shifter he said, “it looks like your drive shaft is about ready to depart your car”. Well the front flex drive shaft coupler was in really bad shape (scary bad condition). It’s not hard to fix, with the exception of drilling out the exhaust flange bolts. I replace the exhaust flange bolts with stainless 1.5” x 5/16” and top lock nuts. The bolts were just barely long enough. You might be more comfortable with 2.0” long bolts.

So I replace the entire driveshaft with a new GM part, about $700. If I had it to do over I would try to save some money by replacing the worn parts, but I was in a hurry to get the car back on the road. I have the Aisin manual transmission and finding the front flex coupler was hard and I think one would have to purchase on the internet. Local part stores could order the aftermarket flex coupler Dorman, but I would strongly suggest buying the OEM SGF coupler, I think it is much more sturdy. I pulled the part numbers off the old drive shaft:

Front Flex Coupler - SGF GAU01-008
Rear Flex Coupler - SGF GAG03-007
I believe these are the dimensions:
GAU01-008 - bolt circle diam 96mm - bolt diam 12mm - bushing length 38mm
GAG03-007 - bolt circle diam 105mm - bolt diam 12mm - bushing length 35mm

These parts are for CTS with the 6 speed Aisin transmission. I can’t speak to other applications, but you should be able to figure it out by googling on the web.

As the bolt circle diameter is smaller on the front coupler I believe it causes more stress and the front coupler is most like the coupler to fail first. My rear coupler looked in good condition, but the front coupler was in really bad shape.

Also the center support bearing was in really bad shape. I believe that the clunking when shifting gears or letting out the clutch was caused by the bad coupler and the thumping was caused by the bad center support bearing.

BEFORE YOU REMOVE THE DRIVE SHAFT ---

1. Pay attention to the bolt pattern where you bolt the drive shaft to the transmission yolk and the differential yolk. The heads of the bolts are on the side of the flex couplers and the nuts are on the side of the steel flange, at least on my car.

2. Do not separate the two halves of the drive shaft before you paint or somehow mark the two halves so they can be aligned when you put the two halves back together. Supposedly the assemble shaft is balance together, and I suspect that the front and back couplers are aligned similar to conventional u-joints. The splines of the drive shaft are not indexed so if you pull apart the two halves without marking them you will not know how to align the splines.


When you remove the drive shaft, there are guide pins on the transmission yolk and the differential yolk, so when you remove the connection bolts you can not pull directly down on the shaft. The front guide center pin is shorter than the rear, so after you remove the front and rear coupler bolts and the center support bearing bolts, push the entire shaft to the rear of the car, and pull down on the front of the shaft. After the front is clear pull forward on the shaft and down on the rear of the shaft.

The front coupler, center support bearing, and the rear coupler will run you about $350 I think. You might have to take the shaft to a shop to have the new center support bearing pressed on.

After I replaced the drive shaft and installed the Creative Steel differential bushing, my Cadillac drives like new.

Good Luck to You,

Dan from Minnesota
 
#12 ·
You can get the sgf flex discs now from your local dealer or oddly enough amazon. Got my front one from an online GM dealer shipped for like a $145. If you let it go too far that front alignment bushing will be bad although I think I have a source for those now after tons of searching. Our manuals use a different one in front the autos use the same front and back.
 
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