Shifter linkage with 700R4

LT1B-Body

Greasemonkey
Feb 25, 2021
191
90
28
Maricopa Arizona
So, I've ran into an issue with the shifter on this car, a 78' Malibu. It had a TH350 previously, I don't know for sure that the column shifter worked with that trans even, I'm assuming so, but regardless it doesn't with the 700R4 I've swapped in. On this car, I would be mostly unbothered by a lack of manual 1st, but I can't get park confidently, regardless of the adjustment.
I've done some reading and tried a few things myself. The engine and transmission in this car, a stock L03 and 4L60, came out of my 91' Caprice wagon (which I have more elaborate plans for). I tried the linkage from that car, which didn't work well. I also played with mixing the upper and lower rods from both car's shifters, that's a big no.

Based on what I'd read, a factory 2004R linkage should work, but I can't exactly pop on over to Summit and grab one. So finding one would a be a quest in and of itself.
Thought about changing to a floor shifter, but those are not cheap. So, not my first choice.
I'm sure I could modify the TH350 linkage, but that would take quite a bit of time I think.

Any ideas? Am I missing something?
 

Rt Jam

G-Body Guru
Mar 30, 2020
621
644
93
Ontario Canada
You are trying to shift a 4 speed auto with a 3 speed shifter.

All the adjustment you are doing is linear adjustments. You probably need to increase the ratio.

If the linkage moves 2" from P to 1st. No matter where you adjust it. It still moves 2"
You need to increase the amount it moves with a lever length change.

Arbitrary numbers^
 

doood

Amateur Mechanic
Sep 24, 2020
620
862
93
My car came with TH250. I used a 2004r shift linkage (including bracket on the prop valve) with my 4L60e and factory column shifter; I dialed in the column shift and transmission detents for park, first and foremost. I placed importance on this so that I don't start the car in gear and run over a kid. I wanted to put a brake-depressed relay for extra safety, but scoped that out (nice but not necessary).

For installation, using the 2004r column shift linkage (ebay), which is subtly different than the th350 shift linkage, I put the column shifter in park, I put the trans in park and I locked the nut down so park on the trans matches park on the column rooster comb. I bought a new grommet for shifter D-loop on the gear selector.

Turns out that I think some of the other detents match up too, like R, maybe D.

I rely on the transmission detents for N, OD, D, 2, 1, L. Those engagements are solid; I have never "knocked it out of gear" with my knee or hand or anything, although I have found myself in D instead of OD a few times.

The column shifter that came with the TH250/350 was not long enough. I've seen people add some rod to the end of the TH350 column shift linkage to get it to work. It may be that some combination may work too, such as 2004r bracket and horizontal bar with the th350 hanging linkage.

You can also do the cable and keep the column shifter. THey sell kits for that too.

Additionally, I have a position indicator on the trans that communicates with my Dakota Digital cluster, so I have a second indication other than counting detents. I rely on that mostly. If I were doing it today, I'd use the 13-pin connector for position-indication and lock-out that came with the 4L60e instead of the one-wire dakota digital position indicator, which is delicate.
 
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Rt Jam

G-Body Guru
Mar 30, 2020
621
644
93
Ontario Canada
Disconnect the linkage at the transmission.

Move the shifter from Park to 1st. Measure how far it moves.

Turn the transmission selector from Park to 1st. Measure how far it moves.
 

CopperNick

Comic Book Super Hero
Supporting Member
Feb 20, 2018
3,436
3,124
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For myself, I shift the 700R4 in my van with the stock TH350E column mounted shift and factory linkage with no problem getting the existing linkage to play nice. The only exception, as has been noted, is that you lose access to 1st/low should you ever want to go granny mode but I just drop it into drive and the T-mission handles all the rest.

Think that locating and acquiring the complete linkage from either a 700R4 or a TH200R4 might help you. The only thing here is that you need the Complete assembly, meaning you have to disconnect the firewall down rod from the tab that sits behind the brake booster, slide under the hulk and drop the pivot plate off the brake proportioning valve, plus the matching mount to it off wherever that is bolted, and all the rest of it all the way to the resident transmission, including the lever on the box and the nut that holds it down. You are replacing your combination with the donor unit as an assembly, no mix and match. The four speed rod combo will already be set to work a four speed auto-box. As for finding one, if all else fails, try Original Parts Group, OPGI and look for a rod set from an 84-88 G-Body.



Nick
 

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