71 Transmission Change
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Heel & Toe
Joined: Jun 2009
Posts: 22
Likes: 0
From: Austin Texas
71 Transmission Change
I have a 71 3-speed automatic 350/270; not a dragster obviously, but still a lot of fun to drive. Top speed I can get her to is just shy of 100 though; just not enough in that 3rd gear to keep those RPMs climbing.
It's been recommended to me to put in a 4-speed auto tranny (or 3-speed with overdrive) to improve the top-end speed.
And before anyone suggests it, I'm NOT interested in putting in a manual tranny; just want to get those RPMs down at higher speeds.
Has anyone done this? It's been recommended to me to put in a 700r4.
Any feedback/advice, good or bad, is appreciated.
m
It's been recommended to me to put in a 4-speed auto tranny (or 3-speed with overdrive) to improve the top-end speed.
And before anyone suggests it, I'm NOT interested in putting in a manual tranny; just want to get those RPMs down at higher speeds.
Has anyone done this? It's been recommended to me to put in a 700r4.
Any feedback/advice, good or bad, is appreciated.
m
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
I am doing a 2004r in place of the 3 speed auto. 2004r and the 350hydro are the same length and use the same spline thus no change neede to drive shaft. Mounting holes to mount are different so you could mod original mount or look at one from Bowtie Overdrive.
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
I am doing a 2004r in place of the 3 speed auto. 2004r and the 350hydro are the same length and use the same spline thus no change needed to drive shaft. Mounting holes to mount are different so you could mod original mount or look at one from Bowtie Overdrive.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You must have a high ratio rear end (3.73 or higher) which is why you 'top-out' so soon with the standard THM-400 tranny [1:1 final ratio in 3rd gear]. If you want to keep the same level of performance {acceleration} but reduce rpm's at higher speeds, you will have to install an overdrive transmission. If you don't mind losing some performance, you could choose to change out the rear gear for a lower ratio, instead. The stock car came with a 3.08 gear. The rpms will reduce by the proportion of change to the rear gear....i.e. changing from a 3.73 to a 3.08 would reduce rpm's about 17%.
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
There are plenty of posts on 200R4 and 700R4 swaps. 200R4 can bolt right in. 700R4 requires a shorter driveshaft. 200R4 never came stock behind a V8, but can be built to take a lot of power. 700R4 has a bad reputation, but a later one, if built right can also handle a lot of power. Do more searches.
Drifting
Joined: Jan 2004
Posts: 1,991
Likes: 3
From: Piscataway NJ
There are plenty of posts on 200R4 and 700R4 swaps. 200R4 can bolt right in. 700R4 requires a shorter driveshaft. 200R4 never came stock behind a V8, but can be built to take a lot of power. 700R4 has a bad reputation, but a later one, if built right can also handle a lot of power. Do more searches.
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