I'm currently swapping a 3500 VVT LZ4 into my 88 Fiero. I got a great deal on a fully rebuilt 4T45 transmission from a Pontiac G6, so that is the transmission I will be using with it. However, all the custom swap brackets out there are for the 4T65E.

Since my coupe is an 88 and originally came with a Duke, the path of least resistance would be to use the "shelf" on the cradle that used to have the single transmission mount setup that Dukes had that year. However, I hated that setup, since the powertrain would annoyingly rock back and forth in the engine compartment too much. So I converted my TH125 to the dual mount setup of the V6 models, and it completely fixed that problem. I don't want to recreate that problem with my swap, so I want to avoid using the single transmission mount setup of the 88 Duke.

So I had an idea for a dual mount setup that I wanted to share with all of you here to have your input.

People who swap a non-electronic 4T60 into a Fiero usually try to find transmission brackets from GM cars that offered both the TH125 and the 4T60, to have brackets that will work with the stock Fiero TH125 mounts.
Using the same logic, I came up with a theory that I'd like to test with all the GM experts here. The Chevy Cavalier and Pontiac Sunfire offered both the 3T40 (a renamed TH125) and the 4T40E, which was later revised and became the 4T45E. Could this mean that Cavalier/Sunfire 4T40E transmission brackets will bolt right up to my 4T45E and the stock Fiero transmission mounts?

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Silver 88 coupe, Duke with TH125C (for now)
White 88 GT, 3800 L67 with 4T65E-HD (sold)
2004 Chrysler Concorde Limited (winter car)

Did you ever find out if this would work?

I don't know if this will be useful in any way (I suspect not, but I'll throw it out there, anyway) but the 3900 in the G6 was bolted to a 4T65E.
I might check to see if the 4T45E and 4T65E used similar brackets, since both trannies were available in the same platform.

In any event, I wish you good luck. I have an LZE (Flex Fuel 3.4) and the 4T45E in my G6. Have often thought it would make a great swap into a Fiero.

[This message has been edited by Raydar (edited 11-17-2019).]

I have an 88 with an automatic iron duke and got a Donor 2009 cobalt with the 2.2 L LAP and 4T45e Where you able to to figure out the tranny mount situation? Also what Axels would you use with the 4T45e?

The 4T60e may bolt right in using stock mounts. We've done this on the earlier cradles, not sure about the 88 though. The 88 will probably need a bit of modification to lengthen the rear mounting area.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "