I’ve been having a conversation in a General section thread about someone’s low mileage 4.9 find, and instead of taking over that thread I want to continue the discussion here for doing the research for doing my 4.9 swap.
The current discussion is about automatic transaxles, and which one to use. It would seem that the transaxle that came with my 4.9 engine has the Deville 3.11 gears, which some say is bad gearing. It appears to be a 4T80E, and others have said they used a 4T60E, so I want to clarify which transaxle I should use with this swap.
Although I already have the engine for my swap, for reference I want to list the years and models you’d want for your 4.9. According to this link from olejoedad...
...it says 91-94 Cadillac. My engine is a 93 Sedan Deville engine, so good. The transaxle, I’m told, has the 3.11 gearing, which I’m told is not the best. According to car-part.com this is a 4T80E, and I’ve seen some folks reference the 4T60E in their swaps. So I need some clarification as to which transaxle we should be talking about, since I will likely be looking for a used or rebuilt transaxle with beater gearing. I need your help here.
The 4T80E was *ONLY* used with the Northstar. You definitely do not have that.
3.11 may refer to the combination of chain ratio and final drive... So a 2.97 final drive with a 1.05 chain ratio = 3.11. I'm not the expert on what parts were actually available or built, however.
3.11 is a lot of gear for a low-revving engine like the 4.9.
[This message has been edited by Will (edited 01-14-2020).]
The 4T80E was never used with the 4.9 V8. The only transmission used with the 4.9 was the 4T60E. The 4T60Ewas used with several GM engines. It is easily identifiable..... No throttle valve cable Vacuum modulator Electrical plug faces forward
A friend had a Fiero with a 4.9 and the 85 - 86 four speed manual 3.65/1 differential. He said the gearing was great, except for on the highway where the revs were too high. He later changed to the F40, it was good except first gear was useless. He later replaced the 4.9 with an LS3.
A friend had a Fiero with a 4.9 and the 85 - 86 four speed manual 3.65/1 differential. He said the gearing was great, except for on the highway where the revs were too high. He later changed to the F40, it was good except first gear was useless. He later replaced the 4.9 with an LS3.
Sounds like 3.71 should do the job.
FYI, under California smog I can’t use a manual transmission so I’ll be sticking with an automatic.
I would find a Seville or Eldorado trans (Or rebuild yours with a a chain/sprocket change.) The 3.33 FDR came stock in the Eldo and Seville, IIRC. So it's already proven to work with the 4.9. (I hated my Deville 2.97s.)
A word of warning... There are at least six different EEPROMs/definition files for the various 4.9 Cadillac vehicles. Most of the differences probably have to do with transmissions and their respective gearing / wiring / connectors, and the different years. You will probably want to source the CALPAK (EEPROM plug-in) from the same vehicle you get the trans from, to ensure compatibility. If you use the wrong program with the wrong trans, you will possibly find yourself running in "limp home" mode. That happened to me when I tried to run a non-compatible program in mine, while I still had the 4T60E. (Others folks may have a better suggestion, or have more insight into what program works with which drivetrain. I welcome that input. That's all I've got.)
Edit - Here's another link from Sinister. Your 4T60E probably already has the 3.33 gears, but in order to realize that final ratio, you will need to swap in a 35/35 sprocket set. Yours probably has the 37/33 set. http://www.gmtuners.com/ima...FWD_trans_ratios.pdf
I would find a Seville or Eldorado trans (Or rebuild yours with a a chain/sprocket change.) The 3.33 FDR came stock in the Eldo and Seville, IIRC. So it's already proven to work with the 4.9. (I hated my Deville 2.97s.)
Edit - Here's another link from Sinister. Your 4T60E probably already has the 3.33 gears, but in order to realize that final ratio, you will need to swap in a 35/35 sprocket set. Yours probably has the 37/33 set. http://www.gmtuners.com/ima...FWD_trans_ratios.pdf
The 3.71 only came in the 4T80E. I promise that that's not what you have. Not if it came bolted to your 4.9.
Yes you can get better low performance by changing the sprockets. Its a medium difficulty job. Its been a while, but I do recall that the pump housing , pump shaft, valve body and input shaft need to be removed to gain access to the sprockets. In other words almost everything under the rear cover. I do not recommend this job for the amateur.
[This message has been edited by Dennis LaGrua (edited 01-14-2020).]
If you used the 33/37 chain ratio from the 3CWW model code with the 3.33 diff from any of the several model codes that had it, you'd end up with 3.73 overall. That's a lot of gear for a low revving 4.9 though.
If you used the 33/37 chain ratio from the 3CWW model code with the 3.33 diff from any of the several model codes that had it, you'd end up with 3.73 overall. That's a lot of gear for a low revving 4.9 though.
I suppose I should define what I want from the swap. Basically, a street car with really good acceleration. I don’t care much about high end speed and “revs”. I don’t need to go much above the speed limit. I might take it to the track for drivers school occasionally. Otherwise, get to freeway speed quickly then cruise.
What speed to you want to cruise at on the freeway? What rear tire size do you have? How high of an engine RPM would you find tolerable at your chosen freeway cruise speed?
If you can answer those questions, and you want the lowest possible ratio for really good acceleration, then your problem is fully defined with a simple answer.
