Gearing questions 7.5 rear

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Stupidquestionspro

Master Mechanic
May 23, 2019
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Tampa Bay Area
Just figured out my rear gear is a 2.41
I think A code peg leg
Seems I forgot an important part
Tires are 225/50/17

Though it seems with the change in transmission it must have changed the final drive I’d guess or something because at 60 it runs 26-2700 rpms which seems rather high to me.

Any ideas?


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Last edited:

fleming442

Captain Tenneal
Dec 26, 2013
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Since you don't have a 4th gear OD, I wouldn't go any lower than a 3.42. It will make it more fun to drive, and seem a helluva lot peppier. HOWEVER, the cruise rpm will be higher than what you already think is high (it is). Are you sure it's shifting into 3rd? According to this: http://www.wallaceracing.com/gear-speed.php you should be at 80 couple mph.
(I put in a 1.00 trans gear, 2.41 rear gear, and a 26" tall tire)
 
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pontiacgp

blank
Mar 31, 2006
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Kitchener, Ontario
with a 2.41 rear end, guessing 26" wheels and a 3 speed transmsion you should only be at 1870 rpm at 60 mph
 
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Stupidquestionspro

Master Mechanic
May 23, 2019
369
107
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Tampa Bay Area
Tires are 225/50/17
So it looks like they are 25.9 inches tall I think based on google so sounds like I need to check my kickdown or figure out what is going on.




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Stupidquestionspro

Master Mechanic
May 23, 2019
369
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Tampa Bay Area
The trans we put in was a TCI street rodder package.

TCI 311138P1 Details
GM

Transmission Part Number: 890-311138
Converter Part Number: 890-241538
Dipstick Part Number: 890-743860
Universal Kickdown Cable Part Number: 890-376900

Looks like gear ratios are

First 2.52
Second 1.52
Third 1.00

Non lock up

Apparently the converter included on a small block is between a 1500-1700 stall

Sounds like I really need to find out if I’m shifting into 3rd or if my tach is lying.




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Stupidquestionspro

Master Mechanic
May 23, 2019
369
107
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Tampa Bay Area
My axle code is 2AJ 201 I believe and from what I read it seems it would be a 2.41 although my tach may be lying it does sound possibly more likely that my trans isn’t shifting to 3rd

Edit: based on the calculator posted above and using the gear ratio for second gear with a 2.41 rear it returns about 2800 around 60 which would kinda fit the situation so I’ll like have to check my shift linkage to ensure it’s correct.

From what I understand the kickdown cable is a very simple set up and shouldn’t effect shifting unless kickdown is engaging trapping it in second? Considering it’s a th350 it doesn’t have a tv cable controlling pressures?

To be sure how exactly do I adjust the kickdown again?


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Stupidquestionspro

Master Mechanic
May 23, 2019
369
107
43
Tampa Bay Area
Yea unfortunately gearing is probably the thing I’ve worked and learned the least on so I didn’t realize how crazy that idea was until I posted so now I have to get down to business and why it’s not shifting.


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Oct 14, 2008
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Melville,Saskatchewan
Have you checked your speedometer with GPS? It and or your tach may be wrong. Actually without a lock up converter like your regular TH350, add 250 to 300 rpm, so around 2100 rpm at 60 mph.
 
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