Wondering if the torque converter rebuild was not so good

DorianL

DorianL

solid fixture here in the forum
Staff member
Welp, I unfortunately changed two variable when I fixed the trans... the 'verter was rebuilt and pump as well.

But I also changed my gearing... well, I went from 26-inch tires to 28. Drag radials.

Now the converter seems a bit slippy. Maybe that is because I am cruising on the highway at same speed but at a lower rpm (not locking up) and the converter slips more like this?

Just wondering if the converter slips more (since its rebuild) before it hits the stall rpm. Or if the bigger tires just make it feel that way...

D
 
DorianL said:
Welp, I unfortunately changed two variable when I fixed the trans... the 'verter was rebuilt and pump as well.

But I also changed my gearing... well, I went from 26-inch tires to 28. Drag radials.

Now the converter seems a bit slippy. Maybe that is because I am cruising on the highway at same speed but at a lower rpm (not locking up) and the converter slips more like this?

Just wondering if the converter slips more (since its rebuild) before it hits the stall rpm. Or if the bigger tires just make it feel that way...

D
Click to expand...
both could be true to some extent if your stall speed is just a bit higher than the cruise rpm, swapping to a larger diam tire may require a rear gear ratio change, the swap from 26" to a 28" tire should have reduced the engine rpm at a 70mph cruise by about 300rpm

viewtopic.php?f=71&t=555
 
Indycars said:
What RPM is the tach showing when cruising on the highway with both tires sizes???
Click to expand...

The problem is the speedo is off when you swap tires... So direct comparison is difficult.

Stall speed should be 2200 - 2400. About 60mph at 1800 rpm but depending on load, +/- 200 rpm.
 
DorianL said:
Indycars said:
What RPM is the tach showing when cruising on the highway with both tires sizes???
Click to expand...

The problem is the speedo is off when you swap tires... So direct comparison is difficult.

Stall speed should be 2200 - 2400. About 60mph at 1800 rpm but depending on load, +/- 200 rpm.
Click to expand...
Just changing from 26" tire to 28" tire doesn't make a big difference in RPM. What rear gear ratio are you running, must be about a 3.36 if you are turning 1800 RPM @ ~60 MPH???. The chart below will give you some kinda idea just how much the RPM would have changed. Also the change would put you closer to the stall speed, making it feel better.....right? The numbers are for the 700R4, but if you want to give me the 2004R ratios, then I would be glad to run the number again.

Just some of my thoughts, what to you all think???

NOTE: [RPM Drop, 26" to 28" Tire] calculations are for the 700R4.
 

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RPM-Calcs60MPH.jpg

looking over that chart it sure looks, like the 3.90-4.11 rear gear is the best choice, for your application, as it would give both a reasonable cruise rpm and good acceleration,


BTW I THINK WERE TALKING a 200R4 transmission here?
with these ratios, making the 4.11:1 rear gear the better choice in my opinion
200-4R
1st 2.740
2nd 1.570
3rd 1.000
OD 0.670
 
I think I'm mainly wondering if this tire change can significantly impact the feel of the trans... Lowering rpm making the converter feel mushy.

For the moment I have 3.42 gears. I used this so I could return to a TH350 if I screwed up. ;). It worked well with 26-inch tires
 
Will see if I can get that lockup going tomorrow + vacuum pump. ;)
 
Ive always liked the results I get with 3.90:1-0r-4.11:1 rear gears with the OD transmissions,which Ive don,e several times in the mid year muscle cars like G.T.Os, ,CHEVELLES,and CAMAROS
the problem is that I also like the way the C4 corvettes look and a 3.73:1 rear gear is max in the stock rear differential, which is a bad joke strength wise, so I,m forced to do a few mods to install a better differential like a DANA 60
 
Here is the updated chart, not much difference between 0.7 and 0.67 OD. Example: 116 RPM - 111 RPM = 5 RPM.
I also added another ratio (4.56)
 

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grumpyvette said:
GREAT!
thats a really useful chart making the rear gear and trans stall speed selection far easier to visualize, especially if youve got access to a dyno power curve print-out for your particular engine.
Click to expand...
Thanks Grumpy!
You are talking about cruising speed right, not going thru the gears???
 
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