denver9244

I have a 350/350 combo in my 71 Vista Cruiser, and it works great. However, I DONT like the stress the three speed puts on my engine at highway speeds. I want to look into maybe putting a 4-speed auto in instead, to give the engine a breather at speeds of 65 mph- plus. Ease of swap and price are my two biggest concerns, not necessarily in that order. Any suggestions?

oldcutlass

Stress? Please note if your running stock gears, your combo was designed to run at highway speeds all day without issue. If your wanting to improve fuel economy then that's a different issue.

denver9244

I am running stock gears. I just DONT like where my RPMs sit at anything over 55. It feels like its running too high.

oldcutlass

What rpm is it running?

oldsmobiledave

Put a taller back tire on it. You are not hurting anything @ 3000 rpm.


If you want an OD trans there are dozens of threads on here regarding 2004R swaps. Keep in mind you will be spending quite a bit of money to purchase the trans, build it right, install it, change the drive shaft & recalibrate your speedo. It will take a lot of driving to get that money back.

denver9244

i dont have a tach, so I dont know where it runs RPM wise. I estimate it to be around 3500 or so. I'm sure its fine, its just higher than I'm comfortable at. New question though: if I run my car for long periods of time in warmer weather, my tranny hesitates to shift. Anyone know why?

oldcutlass

Is the fluid a pretty red color? Although temp shouldn't matter, are the rubber hoses to the modulator and steel line in good shape?

denver9244

It was red last time I checked. I haven't looked at the other two pieces yet.

jensenracing77

If you go to an overdrive transmission you will also have to get a longer driveshaft made for it. That TH350 in that car is a long tail.

Professur

So you're proposing major surgery on a guess?

denver9244

It feels wrong is what I'm getting at. It was only a thought anyways.

Professur

I understand. I posted that to try and shock you back to reality. I had a similar thought with my '85 parisienne. The old trans had lost second so I thought I'd upgrade to the 4 speed. Saw one for cheap on the web and grabbed it. Then I did the math. I'd wind up doing 80+mph before it would shift into 4th. Changing out the diff to match would mean I'd get better acceleration .. but my mileage wouldn't improve a lick. I was turning a lot less rpms at highway cruise than I'd ever thought.

Just a thought ... tire noise can trick you.

denver9244

I also DONT like where it shifts. It shifts from 1st to second at like 10 miles per hour and second to third at like 25. Its probably normal, but I still do not like it.

Fun71

FYI, for many years my car had 3.23 rear gears and short (~25" tall) 245-60-14 tires and the engine turned 3400 RPM or so on the highway. During the summer (Phoenix, AZ with 110+ temps) the coolant would creep up to 210º or so, but slowing down so the RPM dropped to ~3000 brought the coolant temps back to 190º.

My car has survived this for a decade with no adverse effects.

Those shift points are about what my car did when it had a 3.55 rearend under it (light throttle operation).
Shifts are controlled by the governor and the vacuum modulator; lower rear gears translate to lower MPH shift points. WOT shift points are governor controlled as the engine vacuum drops to near zero.
Shift points are also throttle position dependent, so without knowing how you're driving it's hard to speculate.

TexasT

As above, the shift points vary with throttle position. I have a 2004r and 3.42 gears. At light throttle, 1-2 is very early(2k rpm), then 2-3 is about 20mph, 3-4 comes about 40mph and lockup occurs quickly if not accelerating. Now at wot, things happen very differently.
If you choose the 2004r, it will most likely need an overhaul and several parts upgraded and a tv setup and driveshaft if you are swapping the long tail th350
I love mine.

joe_padavano

To get back to the OP's original question, a properly built 200-4R is your best bet. Search on this site, the topic has been covered many times. As noted, you'll need a custom driveshaft. The 200-4R pushes the crossmember back to the TH400 position, so you'll need to change the front and intermediate e-brake cables also. I suspect that you'll really like this trans swap, as not only do you get the O.D. for highway use, but first gear in the 200-4R is 2.74:1 vs. 2.52:1 for the TH350, so off-the-line acceleration will be better as well.

I remain mystified why people think there's some magic to the rear axle ratio and that the engines in early cars won't be able to pull an O.D. trans. I don't care if your Vista has a 2.73 axle, it will still be better with the 200-4R. The 1980s cars with 2.56 gears and the anemic 307 had no problems at freeway speeds with a 200-4R. Your 350 will be fine. Your problem will be the cost of a properly built 200-4R and driveshaft (though it is still cheaper and less invasive than a Gear Vendors unit).