1975 TH350 Swap
Thread Starter
Cruising
Joined: Sep 2024
Posts: 14
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From: CA
1975 TH350 Swap
Hello all. First time posting. I recently picked up a 75 stingray roller and got a 350 mated to a th350. I didn't realize until after I dropped the motor and transmission into car that the trans mount is about 6 inches from the crossmember. Would I be better off making the th350 work or pick up a th400 and just swap them out? What all will I need to make the th350 work with my application? Can I grab a th400 from any vehicle or does it have to come from a corvette for best fitment? Any and all help is appreciated.
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From: Sunshine Coast, Queensland, Australia
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Is the situation that the car only has 2 pedals?
Was this a automatic car before?
Just trying to understand why your putting an Auto in.
Anyway, lots of L48 C3's came with a TH350. I think all you need is a bracket that goes from the trans to the crossmember.
I'm certainly no expert on Automatics. But many on here are. But I am certain you can make that trans fit.
Was this a automatic car before?
Just trying to understand why your putting an Auto in.
Anyway, lots of L48 C3's came with a TH350. I think all you need is a bracket that goes from the trans to the crossmember.
I'm certainly no expert on Automatics. But many on here are. But I am certain you can make that trans fit.
Race Director
Joined: Oct 2000
Posts: 12,682
Likes: 3,135
From: Shamong, NJ
It sounds to me like you might be missing the transmission support bracket that attaches to the crossmember. This is the support the mount cushion itself attaches too. Switching to a TH400 won't help if you don't have the support bracket, as they mount in the same location as the TH350 does.
If you don't have the bracket in the link below, then that is why your trans is coming up short of the crossmember.
https://www.volvette.com/SH101H.html
As an FYI, 1975 was the last year the TH400 came in all Corvettes ordered with an automatic. For 76 & 77 the TH350 came behind the base L-48 350 and the TH400 came with L-82's. By 1978 all automatic Corvettes used the TH350.
If you don't have the bracket in the link below, then that is why your trans is coming up short of the crossmember.
https://www.volvette.com/SH101H.html
As an FYI, 1975 was the last year the TH400 came in all Corvettes ordered with an automatic. For 76 & 77 the TH350 came behind the base L-48 350 and the TH400 came with L-82's. By 1978 all automatic Corvettes used the TH350.
Racer
Joined: Jul 2018
Posts: 331
Likes: 123
From: Sandusky, OH
350 TH is less weight to carry. Takes less HP to operate. Needs different driveshaft yoke( dia. & spline count). Stock shifter should work, but trans bracket is different. Driveshaft length is different by 7/8”, IIRC.
400 TH is one brute mother jamma. Can handle 750 HP with a DIY rebuild. First gear ratios are similar. Converter purchase is same units. Electric switch for kick down. If your gonna beat on it, it can handle it.
But..budget considerations… 200 4R or TKX …overdrive for cruising at hi-way speeds. Stump pulling first gear ratio. Same length as 350 TH for 200 4R. Crossmember mount similar location to 400 TH on 200 4R. TKX buy as a kit, no pieces, parts shopping.
It all depends on your end view of how you want to use the Corvette and what you budget can absorb.
Thats all I can think of…
Steve O.
400 TH is one brute mother jamma. Can handle 750 HP with a DIY rebuild. First gear ratios are similar. Converter purchase is same units. Electric switch for kick down. If your gonna beat on it, it can handle it.
But..budget considerations… 200 4R or TKX …overdrive for cruising at hi-way speeds. Stump pulling first gear ratio. Same length as 350 TH for 200 4R. Crossmember mount similar location to 400 TH on 200 4R. TKX buy as a kit, no pieces, parts shopping.
It all depends on your end view of how you want to use the Corvette and what you budget can absorb.
Thats all I can think of…
Steve O.
Thread Starter
Cruising
Joined: Sep 2024
Posts: 14
Likes: 0
From: CA
Yes, the car was originally an automatic with the th400. Aside from the transmission support bracket, what all would I need to make the th350 work? Although a 750 HP corvette sounds amazing, I am looking to make this my daily driver with the occasional spirited drives on the highway and canyons. Thank you all for the replies and input.
Race Director
Joined: Oct 2000
Posts: 12,682
Likes: 3,135
From: Shamong, NJ
Yes, the car was originally an automatic with the th400. Aside from the transmission support bracket, what all would I need to make the th350 work? Although a 750 HP corvette sounds amazing, I am looking to make this my daily driver with the occasional spirited drives on the highway and canyons. Thank you all for the replies and input.
Last edited by gbvette62; Sep 6, 2024 at 08:00 PM.
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