Gearing questions 7.5 rear

  • Thread starter Stupidquestionspro
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Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
254
28
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

fleming442

Geezer
Dec 26, 2013
6,417
113
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)
 
Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
254
28
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

Stupidquestionspro

Master Mechanic
May 23, 2019
254
28
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

Stupidquestionspro

Master Mechanic
May 23, 2019
254
28
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

Stupidquestionspro

Master Mechanic
May 23, 2019
254
28
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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olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
4,504
113
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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