GM AC Delco transmission oil

[datzenmike]

I have been running a no-name semi synthetic 80w90 gear oil in my transmissions for years. First thing it did was wet the rear seal and begin dripping which most synthetic do because it is so slippery ir will slip past old seals that have no problem holding normal 90w GL-4. A simple $4 seal and the problem is fixed.

 

I noticed the transmission wasn't noisier or quieter after removing the old GL-4 EP gear oil for the no name brand semi synthetic, but the gears shifted with a pleasant and positive clicking sound. The dogleg up shift to third is, and has always been, 'slow'... so I don't bother forcing it. Fifth has always been a firm shove over through the neutral gate and up. Of all the gear changes this one, if not done positively, will most likely result in the clutch coming up and the gear missed. Maybe because it is used the least? or because it's an over drive? Otherwise up shifting is normal and uneventful.

 

Down shifting to second and first is harder than up shifting and the effort increases if the speed change is higher. There is no grinding but you do have to pull firmly into second for a corner in town and push hard to get into first. Generally I just slow down more and it slips in as I near a stop but sometimes the light changes and you are caught in second with cars behind you and need to get into first quickly. This seems fine and I'm used to it and see no problems...it is what it is.

 

I don't drive in cold weather and mainly in the 3-4 months in the summer but when starting off 'cold', the first few shifts into second are more effort than when the transmission is warming or warmed up. I have found that pulling back and slightly towards my right knee seems to work the best and revving up up through first a bit more helps get it into second easier than shifting right away. This could be due to the oil being thicker and slowing the spinning gears faster. 

 

 

I was reading on the 510 Realm of Mazda and Toyota dealers using a GM friction modified synchromesh oil for better shifting and Datsun owners trying it. It's brass synchromesh safe. The results and testimonials are enthusiastic! Better shifting all round and noticeably in cold weather. Quieter too. It goes on and on...

 

So three weeks ago I got two liters of this AC Delco oil and replaced the semi synthetic that was in my transmission. It looks slightly orange and is noticeably thin like engine oil and poured in through the funnel almost as fast as I could pour it. Not wanting to jump on the band wagon, I decided to just drive around for a while and see if later I would look back and notice anything. Here are my impressions...

 

Transmission is not noticeably quieter... no change.... I think.

 

On cold start up, shifts into second are easier and less balky than they used to be. I can shift at much lower speeds. No other changes. When warm it is pure silk.The dogleg to third which always felt slow has improved. It shifts just easier enough to be noticed. Fifth is also just noticeably easier.

 

Down shifting is the most notable improvement. Second and first are the big winners here and I can down shift much easier and have started doing so more often!

 

Was it worth the $17/liter I paid? I think so. If I was changing from ordinary GL-4 80w90 to this I think the results would have been much more dramatic. If running a synthetic oil already, maybe less improvement or none.

 

BTW this oil is manufactured by Shell I believe and re-labeled for use by Chrysler and GM AC Delco under their own part numbers, probably Ford has it too. Maybe some of those 'brand name' colored synthitic oils are the same stuff???

 

[Stoffregen Motorsports]

Mike, thanks for the info.

 

I don't usually have the luxury of experimentation. Since most of the trucks I build are customer vehicles, I am not likely to want to risk a comeback. A few years ago I looked into this very issue for a customer who insisted his transmission needed to be rebuilt. I tore the cases off and inspected the trans to find everything in pristine condidtion. So I called a friend who works for Redline oil and he reccommended MT90 gear oil. The trans was put back together and re-installed into the truck with the new gear oil and it made all the difference. I didn't tell the customer that I did not rebuild it (nor did I charge him for a rebuild), but I let him take it and drive it and he thanked me for fixing the problem.

 

Point being, I bet the A/C Delco oil is similarly formulated to the Redline, but it's probably 1/2 the price. Again, thanks for the info. I know you put a lot of thought into your experiments so now I can try this without worry of a comeback.

 

Matt

[Scgreen620]

Very interesting .. It would be cool if you can update.. Maybe have before and after of the transmission ..

[datzenmike]

I have been running a no-name semi synthetic 80w90 gear oil in my transmissions for years. First thing it did was wet the rear seal and begin dripping which most synthetic do because it is so slippery ir will slip past old seals that have no problem holding normal 90w GL-4. A simple $4 seal and the problem is fixed.

 

I noticed the transmission wasn't noisier or quieter after removing the old GL-4 EP gear oil for the no name brand semi synthetic, but the gears shifted with a pleasant and positive clicking sound. The dogleg up shift to third is, and has always been, 'slow'... so I don't bother forcing it. Fifth has always been a firm shove over through the neutral gate and up. Of all the gear changes this one, if not done positively, will most likely result in the clutch coming up and the gear missed. Maybe because it is used the least? or because it's an over drive? Otherwise up shifting is normal and uneventful.

 

Down shifting to second and first is harder than up shifting and the effort increases if the speed change is higher. There is no grinding but you do have to pull firmly into second for a corner in town and push hard to get into first. Generally I just slow down more and it slips in as I near a stop but sometimes the light changes and you are caught in second with cars behind you and need to get into first quickly. This seems fine and I'm used to it and see no problems...it is what it is.

 

I don't drive in cold weather and mainly in the 3-4 months in the summer but when starting off 'cold', the first few shifts into second are more effort than when the transmission is warming or warmed up. I have found that pulling back and slightly towards my right knee seems to work the best and revving up up through first a bit more helps get it into second easier than shifting right away. This could be due to the oil being thicker and slowing the spinning gears faster. 

 

 

I was reading on the 510 Realm of Mazda and Toyota dealers using a GM friction modified synchromesh oil for better shifting and Datsun owners trying it. It's brass synchromesh safe. The results and testimonials are enthusiastic! Better shifting all round and noticeably in cold weather. Quieter too. It goes on and on...

 

So three weeks ago I got two liters of this AC Delco oil and replaced the semi synthetic that was in my transmission. It looks slightly orange and is noticeably thin like engine oil and poured in through the funnel almost as fast as I could pour it. Not wanting to jump on the band wagon, I decided to just drive around for a while and see if later I would look back and notice anything. Here are my impressions...

 

Transmission is not noticeably quieter... no change.... I think.

 

On cold start up, shifts into second are easier and less balky than they used to be. I can shift at much lower speeds. No other changes. When warm it is pure silk.The dogleg to third which always felt slow has improved. It shifts just easier enough to be noticed. Fifth is also just noticeably easier.

 

Down shifting is the most notable improvement. Second and first are the big winners here and I can down shift much easier and have started doing so more often!

 

Was it worth the $17/liter I paid? I think so. If I was changing from ordinary GL-4 80w90 to this I think the results would have been much more dramatic. If running a synthetic oil already, maybe less improvement or none.

 

BTW this oil is manufactured by Shell I believe and re-labeled for use by Chrysler and GM AC Delco under their own part numbers, probably Ford has it too. Maybe some of those 'brand name' colored synthitic oils are the same stuff???

 

Well this is the immediate results reported after 3 weeks of driving. If replacing the original 90 weight gear oil, the results would have been an immediate WOW!!!!! Even more dramatic if during the winter when it's colder. I already had a semi synthetic oil in it so the results were not as dramatic. (and I'm not so easily impressed) After several weeks I slowly came to realize the up and specially the down shifting was definitely improved. I remembered how it was to drive in the past and compared it to the present and it IS better. If you are running the proper factory recommended 80W90 GL-4 oil and are planning a future change (should be changed every 30K miles) and are finding GL-4 harder and harder to find, try the AC Delco synthetic oil.

[Stoffregen Motorsports]

Yes, cold weather improvements. Sounds exactly like the Redline MT90.

[datzenmike]

Probably the basic formula from Shell.

[datzenmike]

Well I have put about 3K highway miles trip to Canby then up to Calgary and back home running just under 60MPH max but probably averaging 50-ish and the maybe 40% on tertiary roads at 45-ish and even less. Hell I was on holiday and was in no hurry, plus the last month going maybe 3/4 tank in town.

 

Transmission is no louder than before... slight  counter bearing sound at steady speed when car changes from coast to load or load to coasting, normal for a used '79 zx I found in a junkyard for free and was used in my 620 for 10 years and now in my 710, lord knows the mileage on it.

 

Before when shifting cold, and often when warmed up, the engine revs would drop below the next gear before I could get it in gear and the clutch out making for a balky sounding shift. Now the transmission shifts fast enough to catch the revs just right for seamless gears. Shifts continued to be silky smooth and faster when shifted with normal effort. Third and fifth were particularly 'slow' before and now they are effortless.

 

Downshifts again are so much easier now that I find myself looking forward to them more. Before, I down shifted when it began to lug and it wasn't much fun.

 

So, cost me $40 to make driving both easier and more enjoyable. Best $40 I ever spent with my clothes on.