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Hello Gentlemen, it's been a while. I was able to drive my car yesterday for the first time in about three years, after rebuilding the carb and brake master cylinder...
I'm having an issue with my R11's overdrive engagement. When I reach the appropriate speed and let off the gas, I can hear and feel the car kick into OD - except it won't maintain speed once it's shifted. The car will slow down until I give it enough gas to kick down. Does this sound like an electrical or mechanical issue? Any tips where to start troubleshooting? I've looked through the BW OD manual and I'm not sure my symptoms are covered, although I may be misunderstanding the terminology.

Thanks!

Excuse my sarcasm, just in a mood today. Check to be sure the wastegate on the turbocharger is not opening too soon...or that the drive belt on the supercharger is not slipping.

To me sounds very unlikely related to the overdrive, more of a power issue...? I know this sounds silly, but put your hand on the trans/overdrive sections after a drive and make sure something ain't too hot...and make darn sure your fluids are up to level. just saying...

It sounds like bad petrol to me especially as it's been parked for so long. What you described is exactly what I experienced on one of my own cars where the lower gearing without overdrive would move the car but not enough power once it was engaged to do so.

By the way, I doubt that everyone on this forum are men so "gentlemen" might not be in the best of taste!

David, no worries on the sarcasm, thanks for the reply. I really don't think it's a power issue though. The OD has worked perfectly before, and this feels different. Before, I could let off the gas, let the OD shift/engage, and reapply the gas and the car would maintain its speed or accelerate if I asked it to. Now it almost feels like a slipping clutch, and won't maintain 45 on flat ground in OD. This happened the last time I drove it three years ago as well. I thought maybe something was gummed up in the unit preventing complete engagement, so I drained it, filled it with ATF, and ran the car with the rear end in the air, and refilled with fresh Lucas gear oil. The first stop yesterday was to the gas station, added 12 gallons of clear 92.

Any suggestions?

P.s. the belt on my supercharged car is just fine 😜https://bringatrailer.com/listing/2006-mercedes-benz-cl/

One of the amazing functions of the Borg Warner OD system is that when the system is dropping out of OD, the electrical system momentarily shorts the ignition output at the distributor in order to ensure there is no engine torque through the overdrive for a moment.
Sounds as though perhaps the portion of that circuit that goes through the R11 kick down switch may keep the circuit shorted.

I would start with the kick down switch. Either remove and spray some electrical contact cleaner into it, or replace it. Getting the cleaner into it isn't easy, but you can also dunk and soak it, exercise it a bunch of times to make the contacts scrape each other clean.

The other part of this circuit is a set of contacts in the solenoid.

Take a look at the circuit diagram on this website and you may get more insight:

https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=20645&forum=1&post_id=203036#forumpost203036

Hope this helps,
Pat

Pat, thank you for the suggestion, I'll try that this weekend.

On another note, digging around the internet I found this on "Fifth Avenue Internet Garage":

"Do NOT use any synthetic transmission oil / grease in a transmission with a Borg Warner Overdrive. The rollers inside of the O/D transmission that free wheel and lockup the transmission will be too slick with the synthetic oil causing the O/D to not lockup. If someone has installed the synthetic transmission lube, you will have to remove the transmission and disassemble it completely and clean all of the individual internal parts. You CANNOT flush out the transmission with it in the car and get all of the synthetic transmission fluid out of the transmission. So use ONLY non-synthetic transmission lubricant as per factory original or modern 80/90 non-synthetic gear lubricants."

Does anyone here have any similar experience? Seems like it could be my issue...

Source link:http://fifthaveinternetgarage.com/tech_tips_what_transmission_fluid_not_to_use.php

I would chalk that up to a new form of internet hysteria. Yes, the overdrives do work better with normal GL-1 rated gear oil but synthetic oils are not the overdrive equivalent of ebola virus.

Besides, when the car is operating in overdrive, the rollers are not transmitting power and just coast along in their little cage.

If indeed your OD is absorbing a lot of power then it will quickly get very hot, so it would be wise to check it but that is quite unlikely. I would do a careful timing check first, then have a good look at the air filter and carb after that.