3 Speed To 4 Speed Detent Bracket Upgrade-Floor Shift

g3chevy

Apprentice
Jan 30, 2019
96
33
Spring, Texas
Not sure if this has been covered but I wasn't able to find any info on it. Since I wasn't able to shift into 1st I was suspect of the detents on the floor shifter bracket. After comparing it to a 4 speed shifter out of an 86 Grand Prix that had a 200-4R I noticed they were slightly different. So I drilled out the factory rivets on the detent plate on both shifters and did a side to side comparison. So obviously the 4 speed has an extra detent that allows for shifting down into 1st. So I drilled out the rivets on the 3 speed version and swapped out the plates. Riveted back together and road tested it this week. Works great. I'm thinking the other option would be just to grind in another notch on the plate. Would be great to get your thoughts on this.

3 Speed-4 Speed Detent Plate Comparison.jpg 4 Speed-3 Speed Detent Plate Comparison.jpg Shifter Detent Plate-Side By Side.jpg 4 Speed Shifter Detent Plate Installed-Front.jpg 4 Speed Shifter Detent Plate Installed.jpg
 

UNGN

Comic Book Super Hero
Sep 6, 2016
3,061
113
Southlake, TX
Back in the 90's I did 700R4 swap in my '72 Chevelle and a company called "shiftworks" made new detent plates that bolted right in hassle free.

Since Most performance G-bodies came factory with 4 speed autos, there probably isn't much need for a standalone bracket for a swap.
 

g3chevy

Apprentice
Thread starter
Jan 30, 2019
96
33
Spring, Texas
Good to know. I'm about to put a 200-4R in my 75 Chevelle and wondered if I could somehow make one of these plates work. I'll see if I can find an aftermarket supplier that may have one that will fit my shifter. Thanks for the info.
 

UNGN

Comic Book Super Hero
Sep 6, 2016
3,061
113
Southlake, TX
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Rktpwrd

Comic Book Super Hero
Supporting Member
Feb 2, 2015
3,265
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Calgary, Alberta, Canada
Since Most performance G-bodies came factory with 4 speed autos, there probably isn't much need for a standalone bracket for a swap.

I respectfully disagree. Sorta.
While this may be true for performance G bodies, the majority of G’s (and certainly the older “A” bodies out there) are non performance versions and were never offered with an overdrive 4 speed option. And with the performance of regular run-of-the-mill daily driver type cars out there now, our older antiquated 3 speed auto G bodies could all benefit from an overdrive gear just to be able to keep up with traffic and cruise comfortably on the highway.

I was fortunate enough to obtain a 4 speed shifter for my Cutlass from a member on here a couple years ago, but at the time I definitely could’ve used this information to modify my existing 3 speed console shifter. I think regardless of whether there is a demand for a new standalone part or not, the information on how to modify an older existing 3 speed gate would be helpful to many G body owners.
Just my opinion.

I say go for it, and post back with the results. Available shifter gates for mid 70’s Chevrolet’s don’t help the guys out there with Pontiacs, Oldsmobiles, Malibus etc.
 
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UNGN

Comic Book Super Hero
Sep 6, 2016
3,061
113
Southlake, TX
There 100's of thousands of TH350/TH200 G-bodies built, but only a tiny percentage of them have a swapped 4 speed auto and if they needed a shifter, there were 3-4 years of factory shifters built vs. an A-body, Nova, 1st/2nd gen F-body, etc where there no factory solution and a potential commercial market..

Maybe someday, something will be commercially available, but I doubt it, event though a guy with a LASER/waterjet cutter could make these detent plates pretty cheaply.
 
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ssn696

Living in the Past
Supporting Member
Jul 19, 2009
4,970
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Permanent Temporary
If somebody has one of these, can you put the plate on a scanner, make a pdf, and post it in the tribal knowledge section of the Forum? If its a file-to-fit, that could be very helpful data.
 

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