turbo 350

essexcoupe3131

I all, this carry s on from carb thread, I checked the diff ratios last night

the ratio is 3.5 as per what I thought I had installed

I have a short shaft turbo 350, do these all finish at 1;1 in top gear or is it possible they have different ratios?

Is there any way to identify 1 if it does have another ratio set without pulling the whole thing down?, as you know this is fully painted and I havent seen any tags on it



Thanks



Mike

Lee ODell

The length of the transmission does not change the gear ratio. The turbo 350 is l:l in high gear. The long and short transmissions were for different lengh wheel base cars.



Thanks for sharing information on your car.



Have a good day. Lee

essexcoupe3131

Hi Lee, i have been told by a guy here that they are not always 1:1 in the final ratio and was trying to figure out how to identify, as it still brings me back to why I am doing 4k at 60 MPH where I should be doing 2.3-2550 revs at this speed



thanks Mike

[Deleted User]

essexcoupe3131 wrote:

Hi Lee, i have been told by a guy here that they are not always 1:1 in the final ratio and was trying to figure out how to identify, as it still brings me back to why I am doing 4k at 60 MPH where I should be doing 2.3-2550 revs at this speed



thanks Mike

All TH-350 & TH-400 transmissions have a 1:1 final drive ratio. However, unless you are using a lock-up converter (TH-350C) style trans, you will have 200-300 rpm or more "slip" for lack of a better term, due to the fluid coupling properties of the torque converter. Below is a ratio calculator that I used frequently and is quite accurate:



http://www.ringpinion.com/Calc_RPM.aspx

Ol racer

I echo that all Turbo 350's I have are direct drive 1:1 in high gear. Could it be not shifting into high gear or do you have a low ratio Rear End gear like 3.90 or 4.10, or possibly small circumfrence tires?

I have 3.42 gear in one car and it doesnt rev like that at 60mph....

essexcoupe3131

Hi Old Racer,This is the specs turbo 350, 3.5 gears in a 9" 18" Boyd with 28.35" high tires x 245 wide, this has left me dum founded, its been on a rolling road and speed o calibrated to suit and matches the rolling road

Question, is it possible when it was on the rolling road if this was set up in 2 nd gear this would give a false reading in top?



Thanks Mike

[Deleted User]

Being in 2nd gear would do it:



AUTOMATIC

Trans Type First Second Third Fourth Fifth

ALLISON 1000 3.10 1.81 1.41 1.00 0.71

POWERGLIDE 1.82 1.00 - - -

POWERGLIDE 1.76 1.00 - - -

Turbo 4L60 3.06 1.62 1.00 0.70 -

Turbo 4L60E 3.06 1.62 1.00 0.70 -

Turbo 4L80 2.48 1.48 1.00 0.75 -

Turbo 4L80E 2.48 1.48 1.00 0.75 -

Turbo 350 2.52 1.52 1.00 - -

Turbo 400 2.48 1.48 1.00 - -

Turbo 200-R4 2.74 1.57 1.00 0.67 -

Turbo 700-R4 3.06 1.62 1.00 0.70 -

Lee ODell

Mike, where does this guy get his information from?



I believe you may have to disassemble the trans to answer your question.



I believe the problem may be coming from elsewhere.



1. All transmissions have speedometer gears of different ratios to compensate for rear end gear ratio and tire combinations. There may be an error there. A speedometer shop can easily check and correct any errors that may exist.



2. Or there may be a tacometer error. I had that happen to me once.



3. Or you have a much higher stall speed torque coverter than you thought. We have a car running around here that sounds like he's going 80 mph down a 35 mph road but when he goes by it doesn't appear he is even going 30 mph.



Try checking 1 - 3 before tearing the trans apart. I'm looking forward to hearing about the solution to your problem.



I hope these suggestion will be of help.



Have a good day. Lee

Lee ODell

essexcoupe3131 wrote:

Hi Old Racer,This is the specs turbo 350, 3.5 gears in a 9" 18" Boyd with 28.35" high tires x 245 wide, this has left me dum founded, its been on a rolling road and speed o calibrated to suit and matches the rolling road

Question, is it possible when it was on the rolling road if this was set up in 2 nd gear this would give a false reading in top?



Thanks Mike

Mike , I think you have answered you own question.



Second gear ration 1.52 X 3.50 = 5.32 gear ratio.



60 MPH X 5.32 x 336 DIVIDED BY 28.35 tire diameter = 3783.11 RPM plus torque coverter slippage =4k



Have a good day. Lee

Lee ODell

Sorry about my spelling (ration) ratio. My fingers shake and sometimes they hit the wrong keys.



Lee

essexcoupe3131

Thanks Guys, I think I should go back to the rolloing road and have it checked and check out the tach as well, I am working off the infomation the instruments are giving me

Will let you know