: Lost 5th & 6th gear on the way to work this morning



V8V
03-07-13, 09:12 AM
Cruising at 70, and bumped the cruise up by 2 to go around someone. A small bang/pop, and the engine starts to rev. 5th and 6th are gone, but 1st-4th and reverse all work fine. No drama, grinding noises, etc. My first thought was that I lost my clutch until I found that 4th was normal. 162k highway miles. Searching implies transmission, not linkage. Now what?

I could probably change the transmission my self, but rebuilding it myself doesn't sound like a good plan. I'd be fine with a low mileage used one, but a quick Cleveland Pick a Part search came up empty. A Jasper rebuild might be ok. I spend a lot of time on the highway, and never drive it hard. I'll keep searching for a low mileage used one.

Thoughts?

Thanks,
V8V.

rand49er
03-07-13, 10:28 AM
I've been warned many times on here to not shift into 6th gear too early (especially below 40 MPH), but wait till like 50 MPH or above ... that it's hard on 6th gear. At 162k miles, I'm wondering if you've experienced what I've been warned about.

V8V
03-07-13, 11:07 AM
With light acceleration, I normally shift at about 45 to try to keep the RPM's down and save gas. I use a LOT of gas. I always thought that a T56 should last forever under highway driving.

I might have also been low on fluid. This fall I topped it off because of a drip from the tail seal. When I opened the plug, it hissed like it was under pressure. I was suspecting a clogged/pinched vent tube, as the tail seal was replaced once under warranty. I wasn't going to do anything with it until the weather warms up here. It still had an occasional drip, but nothing major

Cadillac Cust Svc
03-07-13, 11:11 AM
V8V, I know you're seeking input from the community, so it's great that rand49er has already chimed in and I hope more members continue to do so. If you continue to have concerns and would like to involve a dealership, please feel free to contact me if you would like Customer Service to work with you and your dealer towards a resolution. I'm reachable via email at Katie_Lucille@gmexpert.com.

Best,

Katie
Cadillac Customer Service

darkman
03-07-13, 11:44 AM
If it were mine I would contact RPM Transmission. They have installers located in various states. They can rebuild yours, or if they have a core in stock they can ship a rebuilt unit for exchange. I don't trust just anybody to rebuild a T-56.

FuzzyLogic
03-07-13, 12:45 PM
With light acceleration, I normally shift at about 45 to try to keep the RPM's down and save gas. I use a LOT of gas. I always thought that a T56 should last forever under highway driving.

Un-freaking believable.

RPM is, at best, a secondary factor in determining fuel consumption. Engine load means almost everything. If your idea of "light acceleration" actually means flooring the pedal at 1100 RPM, you're actually achieving the opposite if your goal because the engine is super heavily loaded at an RPM where it is also the least efficient. And in the process, you were trashing your transmission.

I'm sorry that you blew up your transmission, but frankly, I wished this would happen more often so that people would stop lugging their cars around.

9t8z28
03-07-13, 02:20 PM
Un-freaking believable.

RPM is, at best, a secondary factor in determining fuel consumption. Engine load means almost everything. If your idea of "light acceleration" actually means flooring the pedal at 1100 RPM, you're actually achieving the opposite if your goal because the engine is super heavily loaded at an RPM where it is also the least efficient. And in the process, you were trashing your transmission.

I'm sorry that you blew up your transmission, but frankly, I wished this would happen more often so that people would stop lugging their cars around.

There is "very little" load on the transmission at 45mph in 6th gear. All of the load is on the engine.

V8V, your tranny was just warn out and is not a common thing to happen.

----------

Call F-Parts in PA. (800) 367-8388 They most likely have a tranny.

V8V
03-07-13, 02:23 PM
Darkman - thanks for the tip. I talked with Jeremy at RPM, and he was very helpful. It sounds like this is very common on high highway mileage cars. The 5th/6th gear is pressed onto short splines.

The price and shipping seemed reasonable. I've got two good independent installers locally, a brother in law that is a service technician at a Cadillac dealership (that has almost no V experience), and a friend of a friend who is the transmission guy at Berger Chevy who works on the Camaro's and Corvettes. I'll get his thoughts to see if he wants to rebuild it.

It sounds like there are no upgrades for the T56 for 5th and 6th gear durability. Everything they offer is for low gear drag racers.

Thanks again,
V8V